Interface and Hardware Component Configuration Guide for Cisco NCS 5000 Series Routers, IOS XR Release 6.3.x
Bias-Free Language
The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
This module describes the configuration of Ethernet Operations,
Administration, and Maintenance (OAM) .
Feature History
for Configuring Ethernet OAM
Release
Modification
Release 6.1.1
Support for the following features was introduced:
Ethernet CFM
Release 6.3.1
Support for the following feature was introduced:
Unidirectional Link Detection Protocol
Configuring Ethernet
OAM
This module describes the configuration of Ethernet Operations,
Administration, and Maintenance (OAM) .
Feature History
for Configuring Ethernet OAM
Release
Modification
Release 6.1.1
Support for the following features was introduced:
Ethernet CFM
Release 6.3.1
Support for the following feature was introduced:
Unidirectional Link Detection Protocol
Information About Configuring Ethernet OAM
To configure Ethernet OAM, you should understand the following concepts:
Ethernet Link OAM
Ethernet as a Metro Area Network (MAN) or a Wide
Area Network (WAN) technology benefits greatly from the implementation of
Operations, Administration and Maintenance (OAM) features. Ethernet link OAM
features allow Service Providers to monitor the quality of the connections on a
MAN or WAN. Service providers can monitor specific events,
. Ethernet link
OAM operates on a single, physical link and it can be configured to monitor
either side or both sides of that link.
Ethernet link OAM can be configured in the
following ways:
A Link OAM profile can be configured, and this profile can be used to set the parameters for multiple interfaces.
Link OAM can be configured directly on an interface.
When an interface is also using a link OAM profile, specific parameters that are set in the profile can be overridden by configuring
a different value directly on the interface.
An Ethernet Link OAM profile simplifies the process of configuring EOAM features on multiple interfaces. An Ethernet OAM profile,
and all of its features, can be referenced by other interfaces, allowing other interfaces to inherit the features of that
Ethernet OAM profile.
Individual Ethernet link OAM features can be
configured on individual interfaces without being part of a profile. In these
cases, the individually configured features always override the features in the
profile.
The preferred method of configuring custom EOAM
settings is to create an EOAM profile in Ethernet configuration mode and then
attach it to an individual interface or to multiple interfaces.
These standard Ethernet Link OAM features are
supported on the router:
EFD
Ethernet Fault Detection (EFD) is a mechanism that allows Ethernet OAM protocols, such as CFM, to control the line protocol state of an interface.
Unlike many other interface types, Ethernet interfaces do not
have a line protocol, whose state is independent from that of the interface.
For Ethernet interfaces, this role is handled by the physical-layer Ethernet
protocol itself, and therefore if the interface is physically up, then it is
available and traffic can flow.
EFD changes this to allow CFM to act as the line protocol for Ethernet interfaces. This allows CFM to control the interface
state so that if a CFM defect (such as AIS or loss of continuity) is detected with an expected peer MEP, the interface can
be shut down. This not only stops traffic flow, but also triggers actions in any higher-level protocols to route around the
problem. For example, in the case of Layer 2 interfaces, the MAC table would be cleared and MSTP would reconverge. For Layer
3 interfaces, the ARP cache would be cleared and potentially the IGP would reconverge.
Note
EFD can only be used for down MEPs. When EFD is used to shut
down the interface, the CFM frames continue to flow. This allows CFM to detect
when the problem has been resolved, and thus bring the interface backup
automatically.
This figure shows CFM detection of an error on one of its
sessions EFD signaling an error to the corresponding MAC layer for the
interface. This triggers the MAC to go to a down state, which further triggers
all higher level protocols (Layer 2 pseudowires, IP protocols, and so on) to go
down and also trigger a reconvergence where possible. As soon as CFM detects
there is no longer any error, it can signal to EFD and all protocols will once
again go active.
Figure 1. CFM Error Detection and EFD Trigger
Ethernet CFM
Ethernet Connectivity Fault Management (CFM) is a service-level OAM protocol that provides tools for monitoring and troubleshooting
end-to-end Ethernet services per VLAN. This includes proactive connectivity monitoring, fault verification, and fault isolation.
CFM uses standard Ethernet frames and can be run on any physical media that is capable of transporting Ethernet service frames.
Unlike most other Ethernet protocols which are restricted to a single physical link, CFM frames can transmit across the entire
end-to-end Ethernet network.
CFM is defined in two standards:
IEEE 802.1ag—Defines the core features of the CFM protocol.
ITU-T Y.1731—Redefines, but maintains compatibility with the features of IEEE 802.1ag, and defines some additional features.
Ethernet CFM supports these functions of ITU-T Y.1731:
ETH-CC, ETH-RDI, ETH-LB, ETH-LT—These are equivalent to the corresponding features defined in IEEE 802.1ag.
Note
The Linktrace responder procedures defined in IEEE 802.1ag are used rather than the procedures defined in Y.1731; however,
these are interoperable.
ETH-AIS—The reception of ETH-LCK messages is also supported.
Ethernet CFM is also supported on subinterfaces. CFM provides immediate update if there is any drop in the connection links
between any or all of the devices connected in a network at the subinterface level. To support Ethernet CFM on subinterfaces,
the interface {HundredGigE | TenGigE | GigE | Bundle-Ether}interface-path-id.subinterface command is updated to include the subinterface path ID. For more information on the configuration, see Configuring CFM MEPs section.
Note
In Cisco IOS XR Release 6.3.1, the CFM on subinterfaces is supported only on Cisco NCS 5001 and Cisco NCS 5002 Routers, and
not supported on Cisco NCS 5011 Routers.
To understand how the CFM maintenance model works, you need to understand these concepts and features:
Maintenance
Domains
A maintenance domain describes a management space for the purpose of managing and administering a network. A domain is owned
and operated by a single entity and defined by the set of interfaces internal to it and at its boundary, as shown in this
figure.
Figure 2. CFM Maintenance Domain
A maintenance domain is defined by the bridge ports that are
provisioned within it. Domains are assigned maintenance levels, in the range of
0 to 7, by the administrator. The level of the domain is useful in defining the
hierarchical relationships of multiple domains.
CFM maintenance domains allow different organizations to use CFM
in the same network, but independently. For example, consider a service
provider who offers a service to a customer, and to provide that service, they
use two other operators in segments of the network. In this environment, CFM
can be used in the following ways:
The customer can use CFM between their CE devices, to verify and
manage connectivity across the whole network.
The service provider can use CFM between their PE devices, to
verify and manage the services they are providing.
Each operator can use CFM within their operator network, to
verify and manage connectivity within their network.
Each organization uses a different CFM maintenance domain.
This figure shows an example of the different levels of
maintenance domains in a network.
Note
In CFM diagrams, the conventions are that triangles represent MEPs, pointing in the direction that the MEP sends CFM frames,
and circles represent MIPs.
Figure 2. Different CFM Maintenance Domains Across a Network
To ensure that the CFM frames for each domain do not interfere
with each other, each domain is assigned a maintenance level, between 0 and 7.
Where domains are nested, as in this example, the encompassing domain must have
a higher level than the domain it encloses. In this case, the domain levels
must be negotiated between the organizations involved. The maintenance level is
carried in all CFM frames that relate to that domain.
CFM maintenance domains may touch or nest, but cannot intersect.
This figure illustrates the supported structure for touching and nested
domains, and the unsupported intersection of domains.
Services
A CFM service allows an organization to partition its CFM maintenance domain, according to the connectivity within the network.
For example, if the network is divided into a number of virtual LANs (VLANs), a CFM service is created for each of these.
CFM can then operate independently in each service. It is important that the CFM services match the network topology, so
that CFM frames relating to one service cannot be received in a different service. For example, a service provider may use
a separate CFM service for each of their customers, to verify and manage connectivity between that customer's end points.
A CFM service is always associated with the maintenance domain that it operates within, and therefore with that domain's maintenance
level. All CFM frames relating to the service carry the maintenance level of the corresponding domain.
Note
CFM Services are referred to as Maintenance Associations in IEEE 802.1ag and as Maintenance Entity Groups in ITU-T Y.1731.
Maintenance Points
A CFM Maintenance Point (MP) is an instance of a particular CFM service on a specific interface. CFM only operates on an interface
if there is a CFM maintenance point on the interface; otherwise, CFM frames are forwarded transparently through the interface.
A maintenance point is always associated with a particular CFM service, and therefore with a particular maintenance domain
at a particular level. Maintenance points generally only process CFM frames at the same level as their associated maintenance
domain. Frames at a higher maintenance level are always forwarded transparently, while frames at a lower maintenance level
are normally dropped. This helps enforce the maintenance domain hierarchy, and ensures that CFM frames for a particular domain
cannot leak out beyond the boundary of the domain.
There are two types of MP:
Maintenance End Points (MEPs)—Created at the edge of the domain. Maintenance end points (MEPs) are members of a particular
service within a domain and are responsible for sourcing and sinking CFM frames. They periodically transmit continuity check
messages and receive similar messages from other MEPs within their domain. They also transmit traceroute and loopback messages
at the request of the administrator. MEPs are responsible for confining CFM messages within the domain.
Maintenance Intermediate Points (MIPs)—Created in the middle of the domain. Unlike MEPS, MIPs do allow CFM frames at their
own level to be forwarded.
MIP Creation
Unlike MEPs, MIPs are not explicitly configured on each
interface. MIPs are created automatically according to the algorithm specified
in the CFM 802.1ag standard. The algorithm, in brief, operates as follows for
each interface:
The
bridge-domain or
cross-connect for the interface is found, and all services
associated with that
bridge-domain or
cross-connect are considered for MIP auto-creation.
The level of the highest-level MEP on the interface is found.
From among the services considered above, the service in the domain with the
lowest level that is higher than the highest MEP level is selected. If there
are no MEPs on the interface, the service in the domain with the lowest level
is selected.
The MIP auto-creation configuration (mip auto-create
command) for the selected service is examined to determine whether a MIP should
be created.
Note
Configuring a MIP auto-creation policy for a service does not
guarantee that a MIP will automatically be created for that service. The policy
is only considered if that service is selected by the algorithm first.
MEP and CFM
Processing Overview
The boundary of a domain is an interface, rather than a bridge
or host. Therefore, MEPs can be sub-divided into two categories:
Down MEPs—Send CFM frames from the interface where they are
configured, and process CFM frames received on that interface. Down MEPs
transmit AIS messages upward (toward the
cross-connect).
Up MEPs—Send frames into the bridge relay function, as if they
had been received on the interface where the MEP is configured. They process
CFM frames that have been received on other interfaces, and have been switched
through the bridge relay function as if they are going to be sent out of the
interface where the MEP is configured. Up MEPs transmit AIS messages downward
(toward the wire). However, AIS packets are only sent when there is a MIP
configured on the same interface as the MEP and at the level of the MIP.
Note
The terms Down MEP and Up MEP are defined in the IEEE 802.1ag and ITU-T Y.1731 standards, and refer to the direction that CFM frames are sent from the MEP.
The terms should not be confused with the operational status of the MEP.
The router only supports the "Down MEP level < Up MEP level" configuration.
This figure illustrates the monitored areas for Down and Up
MEPs.
Figure 4. Monitored Areas for Down and Up MEPs
This figure shows maintenance points at different levels. Because domains are allowed to nest but not intersect (see ), a
MEP at a low level always corresponds with a MEP or MIP at a higher level. In addition, only a single MIP is allowed on any
interface—this is generally created in the lowest domain that exists at the interface and that does not have a MEP.
MIPs and Up MEPs can only exist on switched (Layer 2) interfaces, because they send and receive frames from the bridge relay
function. Down MEPs can be created on switched (Layer 2) interfaces.
MEPs continue to operate normally if the interface they are
created on is blocked by the Spanning Tree Protocol (STP); that is, CFM frames
at the level of the MEP continue to be sent and received, according to the
direction of the MEP. MEPs never allow CFM frames at the level of the MEP to be
forwarded, so the STP block is maintained.
MIPs also continue to receive CFM frames at their level if the
interface is STP blocked, and can respond to any received frames. However, MIPs
do not allow CFM frames at the level of the MIP to be forwarded if the
interface is blocked.
Note
A separate set of CFM maintenance levels is created every time a
VLAN tag is pushed onto the frame. Therefore, if CFM frames are received on an
interface which pushes an additional tag, so as to “tunnel” the frames over
part of the network, the CFM frames will not be processed by any MPs within the
tunnel, even if they are at the same level. For example, if a CFM MP is created
on an interface with an encapsulation that matches a single VLAN tag, any CFM
frames that are received at the interface that have two VLAN tags will be
forwarded transparently, regardless of the CFM level.
CFM Protocol Messages
The CFM protocol consists of a number of different message types, with different purposes. All CFM messages use the CFM EtherType,
and carry the CFM maintenance level for the domain to which they apply.
This section describes the following CFM messages:
Continuity Check
(IEEE 802.1ag and ITU-T Y.1731)
Continuity Check Messages (CCMs) are “heartbeat” messages
exchanged periodically between all the MEPs in a service. Each MEP sends out
multicast CCMs, and receives CCMs from all the other MEPs in the service—these
are referred to as
peer MEPs. This allows each MEP to discover its peer MEPs,
and to verify that there is connectivity between them.
MIPs also receive CCMs. MIPs use the information to build a MAC
learning database that is used when responding to Linktrace. For more
information about Linktrace, see the
“Linktrace
(IEEE 802.1ag and ITU-T Y.1731)” section.
Figure 5. Continuity Check Message Flow
All the MEPs in a service must transmit CCMs at the same
interval. IEEE 802.1ag defines 7 possible intervals that can be used:
3.3ms
10ms
100ms
1s
10s
1 minute
10 minutes
A MEP detects a loss of connectivity with one of its peer MEPs when some number of CCMs have been missed. This occurs when
sufficient time has passed during which a certain number of CCMs were expected, given the CCM interval. This number is called
the loss threshold, and is usually set to 3.
The CCM intervals of 3.3ms and 10ms for the transmission of CCM messages, are not supported. For the CCM intervals of 100
ms, 1 s, 10 s, 1 min, or 10 mins, and the loss threshold value between 2 to 250, ensure that the CCM loss time does not exceed 4 mins. CFM scale is up to a maximum of 500 sessions
for a CCM interval of 100ms.
CFM is supported only on interfaces which have Layer 2 transport feature enabled.
CCM messages carry a variety of information that allows
different defects to be detected in the service. This information includes:
A configured identifier for the domain of the transmitting MEP.
This is referred to as the Maintenance Domain Identifier (MDID).
A configured identifier for the service of the transmitting MEP.
This is referred to as the Short MA Name (SMAN). Together, the MDID and the
SMAN make up the Maintenance Association Identifier (MAID). The MAID must be
configured identically on every MEP in the service.
These are restrictions on the type of MAID that are supported for sessions with time interval of less than 1 minute. The MAID
supports two types of formats on offloaded MEPs:
No Domain Name Format
MD Name Format = 1-NoDomainName
Short MA Name Format = 3 - 2 bytes integer value
Short MA NAme Length = 2 - fixed length
Short MA Name = 2 bytes of integer
1731 Maid Format
MD Name Format = 1-NoDomainName
MA Name Format(MEGID Format) = 32
MEGID Length = 13 - fixed length
MEGID(ICCCode) = 6 Bytes
MEGID(UMC) = 7 Bytes
ITU Carrier Code (ICC) - Number of different configurable ICC code - 15 (for each NPU)
Unique MEG ID Code (UMC) - 4
Maintenance Association Identifier (MAID) comprises of the Maintenance Domain Identifier (MDID) and Short MA Name (SMAN).
MDID only supports null value and SMAN only supports ITU Carrier Code (ICC) or a numerical. No other values are supported.
An example for configuring domain ID null is: ethernet cfm domain SMB level 3 id null
An example for configuring SMAN is: ethernet cfm domain SMB level 3 id null service 901234AB xconnect group 99999 p2p 99999 id number 1
The following table summarizes the supported values and parameters for MDID and SMAN. This table only details the MAID restriction
on the hardware offload feature. There is no MAID restriction for software offload or non-offloaded MEPs.
For Cisco NCS 5500 series routers, "id null" has to be explicitly configured for the domain ID, for hardware offloaded sessions.
Format
MDID
SMAN
Support
Comment
No
2 byte integer
Yes
Up to 2000 entries
No
13 bytes ICCCode (6 bytes) and UMC (7 bytes)
Yes
Up to 15 unique ICC
Up to 4K UMC values
48 bytes string based
1-48 bytes of MDID and SMAN
No
Most commonly used
A configured numeric identifier for the MEP (the MEP ID). Each
MEP in the service must be configured with a different MEP ID.
Dynamic
Remote MEPs are not supported for MEPs with less than 1min interval. You must
configure MEP CrossCheck for all such MEPS.
Sequence numbering is not supported for MEPs with less than 1
minute interval.
In a Remote Defect Indication (RDI), each MEP includes this in the CCMs it is sending, if it has detected a defect relating
to the CCMs it is receiving. This notifies all the MEPs in the service that a defect has been detected somewhere in the service.
The interval at which CCMs are being transmitted.
CCM Tx/Rx
statistics counters are not supported for MEPs with less than1 minute
intervals.
Sender TLV
and Cisco Proprietary TLVs are not supported for MEPs with less than 1min
intervals.
The status of the interface where the MEP is operating—for
example, whether the interface is up, down, STP blocked, and so on.
Note
The status of the interface (up/down) should not be confused
with the direction of any MEPs on the interface (Up MEPs/Down MEPs).
These defects can be detected from received CCMs:
Interval mismatch—The CCM interval in the received CCM does not
match the interval that the MEP is sending CCMs.
Level mismatch—A MEP has received a CCM carrying a lower
maintenance level than the MEPs own level.
Loop—A CCM is received with the source MAC address equal to the
MAC address of the interface where the MEP is operating.
Configuration error—A CCM is received with the same MEP ID as
the MEP ID configured for the receiving MEP.
Cross-connect—A CCM is received with an MAID that does not match
the locally configured MAID. This generally indicates a VLAN misconfiguration
within the network, such that CCMs from one service are leaking into a
different service.
Peer interface down—A CCM is received that indicates the
interface on the peer is down.
Remote defect indication—A CCM is received carrying a remote
defect indication.
Note
This defect does not cause the MEP to include a remote defect
indication in the CCMs that it is sending.
Out-of-sequence CCMs can also be detected by monitoring the
sequence number in the received CCMs from each peer MEP. However, this is not
considered a CCM defect.
Loopback (IEEE
802.1ag and ITU-T Y.1731)
Loopback Messages (LBM) and Loopback Replies (LBR) are used to
verify connectivity between a local MEP and a particular remote MP. At the
request of the administrator, a local MEP sends unicast LBMs to the remote MP.
On receiving each LBM, the target maintenance point sends an LBR back to the
originating MEP. Loopback indicates whether the destination is reachable or
not—it does not allow hop-by-hop discovery of the path. It is similar in
concept to an ICMP Echo (ping). Since loopback messages are destined for
unicast addresses, they are forwarded like normal data traffic, while observing
the maintenance levels. At each device that the loopback reaches, if the
outgoing interface is known (in the bridge's forwarding database), then the
frame is sent out on that interface. If the outgoing interface is not known,
then the message is flooded on all interfaces.
This figure shows an example of CFM loopback message flow
between a MEP and MIP.
Figure 6. Loopback Messages
Loopback messages can be padded with user-specified data. This
allows data corruption to be detected in the network. They also carry a
sequence number which allows for out-of-order frames to be detected.
Linktrace (IEEE
802.1ag and ITU-T Y.1731)
Linktrace Messages (LTM) and Linktrace Replies (LTR) are used to
track the path (hop-by-hop) to a unicast destination MAC address. At the
request of the operator, a local MEP sends an LTM. Each hop where there is a
maintenance point sends an LTR back to the originating MEP. This allows the
administrator to discover connectivity data about the path. It is similar in
concept to IP traceroute, although the mechanism is different. In IP
traceroute, successive probes are sent, whereas CFM Linktrace uses a single LTM
which is forwarded by each MP in the path. LTMs are multicast, and carry the
unicast target MAC address as data within the frame. They are intercepted at
each hop where there is a maintenance point, and either retransmitted or
dropped to discover the unicast path to the target MAC address.
This figure shows an example of CFM linktrace message flow
between MEPs and MIPs.
Figure 7. Linktrace Message Flow
The linktrace mechanism is designed to provide useful
information even after a network failure. This allows it to be used to locate
failures, for example after a loss of continuity is detected. To achieve this,
each MP maintains a CCM Learning Database. This maps the source MAC address for
each received CCM to the interface through which the CCM was received. It is
similar to a typical bridge MAC learning database, except that it is based only
on CCMs and it times out much more slowly—on the order of days rather than
minutes.
Note
In IEEE 802.1ag, the CCM Learning Database is referred to as the
MIP CCM Database. However, it applies to both MIPs and MEPs.
In IEEE 802.1ag, when an MP receives an LTM message, it
determines whether to send a reply using the following steps:
The target MAC address in the LTM is looked up in the bridge MAC
learning table. If the MAC address is known, and therefore the egress interface
is known, then an LTR is sent.
If the MAC address is not found in the bridge MAC learning
table, then it is looked up in the CCM learning database. If it is found, then
an LTR is sent.
If the MAC address is not found, then no LTR is sent (and the
LTM is not forwarded).
If the target MAC has never been seen previously in the network,
the linktrace operation will not produce any results.
Note
IEEE 802.1ag and ITU-T Y.1731 define slightly different
linktrace mechanisms. In particular, the use of the CCM learning database and
the algorithm described above for responding to LTM messages are specific to
IEEE 802.1ag. IEEE 802.1ag also specifies additional information that can be
included in LTRs. Regardless of the differences, the two mechanisms are
interoperable.
Configurable Logging
CFM supports logging of various conditions to syslog. Logging can be enabled independently for each service, and when the
following conditions occur:
New peer MEPs are detected, or loss of continuity with a peer MEP occurs.
Changes to the CCM defect conditions are detected.
Cross-check “missing” or “unexpected” conditions are detected.
AIS condition detected (AIS messages received) or cleared (AIS messages no longer received).
EFD used to shut down an interface, or bring it back up.
EFD
Ethernet Fault Detection (EFD) is a mechanism that allows Ethernet OAM protocols, such as CFM, to control the line protocol state of an interface.
Unlike many other interface types, Ethernet interfaces do not
have a line protocol, whose state is independent from that of the interface.
For Ethernet interfaces, this role is handled by the physical-layer Ethernet
protocol itself, and therefore if the interface is physically up, then it is
available and traffic can flow.
EFD changes this to allow CFM to act as the line protocol for Ethernet interfaces. This allows CFM to control the interface
state so that if a CFM defect (such as AIS or loss of continuity) is detected with an expected peer MEP, the interface can
be shut down. This not only stops traffic flow, but also triggers actions in any higher-level protocols to route around the
problem. For example, in the case of Layer 2 interfaces, the MAC table would be cleared and MSTP would reconverge. For Layer
3 interfaces, the ARP cache would be cleared and potentially the IGP would reconverge.
Note
EFD can only be used for down MEPs. When EFD is used to shut
down the interface, the CFM frames continue to flow. This allows CFM to detect
when the problem has been resolved, and thus bring the interface backup
automatically.
This figure shows CFM detection of an error on one of its
sessions EFD signaling an error to the corresponding MAC layer for the
interface. This triggers the MAC to go to a down state, which further triggers
all higher level protocols (Layer 2 pseudowires, IP protocols, and so on) to go
down and also trigger a reconvergence where possible. As soon as CFM detects
there is no longer any error, it can signal to EFD and all protocols will once
again go active.
Figure 8. CFM Error Detection and EFD Trigger
Flexible VLAN
Tagging for CFM
The Flexible VLAN Tagging for CFM feature ensures that CFM
packets are sent with the right VLAN tags so that they are appropriately
handled as a CFM packet by the remote device. When packets are received by an
edge router, they are treated as either CFM packets or data packets, depending
on the number of tags in the header. The system differentiates between CFM
packets and data packets based on the number of tags in the packet, and
forwards the packets to the appropriate paths based on the number of tags in
the packet.
CFM frames are normally sent with the same VLAN tags as the
corresponding customer data traffic on the interface, as defined by the
configured encapsulation and tag rewrite operations. Likewise, received frames
are treated as CFM frames if they have the correct number of tags as defined by
the configured encapsulation and tag rewrite configuration, and are treated as
data frames (that is, they are forwarded transparently) if they have more than
this number of tags.
In most cases, this behavior is as desired, since the CFM frames
are then treated in exactly the same way as the data traffic flowing through
the same service. However, in a scenario where multiple customer VLANs are
multiplexed over a single multipoint provider service (for example, N:1
bundling), a different behavior might be desirable.
This figure shows an example of a network with multiple VLANS
using CFM.
Figure 9. Service Provider Network With Multiple VLANs and
CFM
This figure shows a provider's access network, where the S-VLAN
tag is used as the service delimiter. PE1 faces the customer, and PE2 is at the
edge of the access network facing the core. N:1 bundling is used, so the
interface encapsulation matches a range of C-VLAN tags. This could potentially
be the full range, resulting in all:1 bundling. There is also a use case where
only a single C-VLAN is matched, but the S-VLAN is nevertheless used as the
service delimiter—this is more in keeping with the IEEE model, but limits the
provider to 4094 services.
CFM is used in this network with a MEP at each end of the access
network, and MIPs on the boxes within the network (if it is native Ethernet).
In the normal case, CFM frames are sent by the up MEP on PE1 with two VLAN
tags, matching the customer data traffic. This means that at the core
interfaces and at the MEP on PE2, the CFM frames are forwarded as if they were
customer data traffic, since these interfaces match only on the S-VLAN tag. So,
the CFM frames sent by the MEP on PE1 are not seen by any of the other MPs.
Flexible VLAN tagging changes the encapsulation for CFM frames
that are sent and received at Up MEPs. Flexible VLAN tagging allows the frames
to be sent from the MEP on PE1 with just the S-VLAN tag that represents the
provider service. If this is done, the core interfaces will treat the frames as
CFM frames and they will be seen by the MIPs and by the MEP on PE2. Likewise,
the MEP on PE1 should handle received frames with only one tag, as this is what
it will receive from the MEP on PE2.
To ensure that CFM packets from Up MEPs are routed to the
appropriate paths successfully, tags may be set to a specific number in a
domain service, using the
tags command.
Currently, tags can only be set to one (1).
CFM on
MC-LAG
CFM on Multi-Chassis Link Aggregation Groups is supported in the
following typical network environment:
The customer edge (CE) device is a dual-homed device that is
connected to two provider edge (PE) point-of-attachment (POA) devices. However,
the dual-homed device operates without awareness of connectivity to multiple
PEs.
The two points of attachment at the PE form a redundancy group
(RG), with one POA functioning as the active POA, and the other as the standby
POA for the dual-homed device link.
As with typical failover scenarios, if a failure occurs with the
active POA, the standby POA takes over to retain the dual-homed device’s
connectivity to the network.
CFM on MC-LAG support can be qualified at two levels:
CFM for the RG level—CFM context is per redundancy group and
verifies connectivity for the entire RG.
CFM for the POA level—CFM context is per point of attachment and
verifies connectivity to a single POA.
Both levels of CFM support have certain restrictions and
configuration guidelines that you must consider for successful implementation.
For more information about LAG, see the
Configuring Link
Bundling chapter in this guide.
RG-Level CFM
RG-level CFM is comprised of three areas of monitoring:
RG Downlink
Monitoring
RG downlink monitoring uses CFM to verify connectivity between
the dual-homed device and the RG.
To configure RG downlink monitoring, be sure that the following
requirements are met:
Down MEPs are configured on the bundle.
Down MEPs on each POA are configured identically, using the same
MEP ID and source MAC address.
This configuration has the following restrictions:
The CCM loss time is greater than the failover time (typically
50 ms), due to the shortest CCM interval of 100 ms that is currently supported,
which results in the shortest CCM loss time of 350 ms.
End-to-End
Service Monitoring
End-to-end service monitoring uses CFM to verify the end-to-end
service between the dual-homed devices.
To configure end-to-end service monitoring, be sure that the
following requirements are met:
A down MEP is configured on the dual-homed device bundle
interface or bundle subinterface.
If optional MIPs are configured, then each POA is configured
with a MIP on the bundle.
Each POA can have a MIP on the uplink interface (if native
Ethernet is used).
The active and standby POA is configured identically.
This configuration has the following restrictions:
The MIP on the standby POA will not respond to loopback or
linktrace requests.
POA-Level
CFM
POA-level monitoing uses CFM to verify connectivity between the
dual-homed device and a single POA.
To configure POA-level CFM, be sure that these requirements are
met:
Down MEPs are configured on bundle members only.
This configuration has these restrictions:
POA-level monitoring is not supported on uplinks between a
single POA and the core.
Supported Features
for CFM on MC-LAG
CFM on MC-LAG supports these CFM features:
All existing IEEE 802.1ag and Y.1731 functionality is supported
on an MC-LAG RG.
CFM maintenance points are supported on an MC-LAG interface.
Maintenance points on a standby link are put into standby state.
Maintenance points in standby state receive CFM messages, but do
not send or reply to any CFM messages.
When a MEP transitions from active to standby, all CCM defects
and alarms are cleared.
Standby MEPs record remote MEP errors and timeouts, but do not
report faults. This means that remote MEPs and their errors will appear in
show commands, but no logs, alarms, MIB traps, or EFD are
triggered and AIS messages are not sent.
When a MEP transitions from standby to active, any CCM defects
previously detected while the MEP was in standby are reapplied and immediate
actions are taken (logs, alarms, MIB traps, EFD, and so on).
Restrictions for CFM
on MC-LAG
To support CFM on MC-LAG, you must consider these restrictions
and requirements:
The CFM configuration must be the same on both the active and
standby POAs.
The CFM state is not synchronized between the two POAs. This can
lead to flapping of the interface line protocol state on POA failover if EFD is
configured. Fault alarms might also be delayed if a failover occurs just after
a fault has been detected.
POA-level CFM monitoring is not supported on a native Ethernet
uplink interface.
MEPs on bundle interfaces at level 0 are not supported.
Loopback, linktrace, and Y.1731 SLA operations cannot be started
from a MEP in standby state.
Checks for configuration consistency of MEP IDs to ensure
identical configuration of POAs is not supported.
Y.1731
SLA statistics can be split between the two POAs if a failover occurs. An
external network management system would need to collect and collate these
statistics from the two POAs.
Restrictions for CFM Support on Subinterfaces
The CFM is not supported on Cisco NCS 5011 Routers.
Up MEPs are not supported.
The CCM intervals of 3.3ms and 10ms for the transmission of CCM messages, are not supported.
CFM scale is up to a maximum of 500 sessions for a CCM interval of 100ms.
For the CCM intervals of 100 ms, 1 second, 10 second, 1 min, or 10 mins, and the loss threshold value between 2 to 250, ensure that the CCM loss time does not exceed 4 mins.
Ethernet Connectivity Fault Management (CFM) is not supported with Maintenance association End Points (MEPs) that are configured
on default and untagged encapsulated sub-interfaces that are part of a single physical interface.
How to Configure Ethernet OAM
This section provides these configuration procedures:
Configuring Ethernet CFM
To configure Ethernet CFM, perform the following tasks:
Note
CFM is not supported for the following:
L3 Interfaces and Sub-Interfaces
Bundle Member Ports
EVPN-FXC
Bridge Domain
VPLS
Configuring a CFM
Maintenance Domain
To configure a CFM maintenance domain, perform the following
steps:
RP/0/RP0/CPU0:router(config-cfm)# domain Domain_One level 1 id string D1
Creates and names a container for all domain configurations and
enters CFM domain configuration mode.
The level must be specified.
The
id is the maintenance domain identifier (MDID) and
is used as the first part of the maintenance association identifier (MAID) in
CFM frames. If the MDID is not specified, the domain name is used as the MDID
by default.
(Optional) Sets the maximum limit of traceroute cache entries or
the maximum time limit to hold the traceroute cache entries. The default is 100
minutes and 100 entries.
Step 5
end or
commit
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn)# commit
Saves configuration changes.
When you use the
end command, the system prompts you to commit
changes:
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:
Entering
yes saves configuration changes to the running configuration
file, exits the configuration session, and returns the router to EXEC mode.
Entering
no exits the configuration session and returns the
router to EXEC mode without committing the configuration changes.
Entering
cancel leaves the router in the current
configuration session without exiting or committing the configuration changes.
Use the
commit command to save the configuration changes
to the running configuration file and remain within the configuration session.
Configuring Services
for a CFM Maintenance Domain
You can configure up to 32000 CFM services for a maintenance domain. To configure services for a CFM maintenance domain, perform the following steps:
RP/0/RP0/CPU0:router(config-cfm)# domain Domain_One level 1 id string D1
Creates and names a container for all domain configurations at a
specified maintenance level, and enters CFM domain configuration mode.
The
id is the maintenance domain identifier (MDID) and
is used as the first part of the maintenance association identifier (MAID) in
CFM frames. If the MDID is not specified, the domain name is used as the MDID
by default.
Step 4
service service-name { down-meps | xconnect group xconnect-group-name p2p xconnect-name}[id[icc-basedicc-string umc-string] | [ [numbernumber]
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn)# service xconnect group X1
Configures and associates a service with the domain and enters CFM domain service configuration mode. You can specify that
the service is used only for down MEPs, or associate the service with a bridge domain where MIPs and up MEPs will be created.
The id sets the short MA name.
Step 5
end or
commit
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# commit
Saves configuration changes.
When you use the
end command, the system prompts you to commit
changes:
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:
Entering
yes saves configuration changes to the running configuration
file, exits the configuration session, and returns the router to EXEC mode.
Entering
no exits the configuration session and returns the
router to EXEC mode without committing the configuration changes.
Entering
cancel leaves the router in the current
configuration session without exiting or committing the configuration changes.
Use the
commit command to save the configuration changes
to the running configuration file and remain within the configuration session.
Enabling and
Configuring Continuity Check for a CFM Service
To configure Continuity Check for a CFM service, complete the
following steps:
RP/0/RP0/CPU0:router(config-cfm)# domain Domain_One level 1 id string D1
Creates and names a container for all domain configurations and
enters the CFM domain configuration mode.
The level must be specified.
The
id is the maintenance domain identifier (MDID) and
is used as the first part of the maintenance association identifier (MAID) in
CFM frames. If the MDID is not specified, the domain name is used as the MDID
by default.
Step 4
service
service-name { down-meps | xconnect
group xconnect-group-name
p2p xconnect-name}[id[icc-basedicc-string umc-string] |
[ [numbernumber]
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn)# service xconnect group X1
Configures and associates a service with the domain and enters
CFM domain service configuration mode. You can specify that the service is used
only for down MEPs, or associate the service with a bridge domain or xconnect
where MIPs and up MEPs will be created.
RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# continuity-check interval 100m loss-threshold 10
(Optional) Enables Continuity Check and specifies the time
interval at which CCMs are transmitted or to set the threshold limit for when a
MEP is declared down.
RP/0/RP0/CPU0:router(config-cfm)# domain Domain_One level 1 id string D1
Creates and names a container for all domain configurations and
enters the CFM domain configuration mode.
The level must be specified. The only supported option is
id [null] for less than 1min interval
MEPS.
The
id is the maintenance domain identifier (MDID) and
is used as the first part of the maintenance association identifier (MAID) in
CFM frames. If the MDID is not specified, the domain name is used as the MDID
by default.
Step 4
service
service-name { down-meps | xconnect
group xconnect-group-name
p2p xconnect-name}[id[icc-basedicc-string
umc-string] |
[numbernumber]
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn)# service xconnect group X1
Configures and associates a service with the domain and enters
CFM domain service configuration mode. You can specify that the service is used
only for down MEPs, or associate the service with a bridge domain where MIPs
and up MEPs will be created.
RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# mip auto-create all ccm-learning
(Optional) Enables the automatic creation of MIPs in a bridge
domain.
ccm-learning option enables CCM learning for MIPs
created in this service. This must be used only in services with a relatively
long CCM interval of at least 100 ms. CCM learning at MIPs is disabled by
default.
Step 6
end or
commit
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# commit
Saves configuration changes.
When you use the
end command, the system prompts you to commit
changes:
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:
Entering
yes saves configuration changes to the running configuration
file, exits the configuration session, and returns the router to EXEC mode.
Entering
no exits the configuration session and returns the
router to EXEC mode without committing the configuration changes.
Entering
cancel leaves the router in the current
configuration session without exiting or committing the configuration changes.
Use the
commit command to save the configuration changes
to the running configuration file and remain within the configuration session.
Configuring
Cross-Check on a MEP for a CFM Service
To configure cross-check on a MEP for a CFM service and specify
the expected set of MEPs, complete the following steps:
RP/0/RP0/CPU0:router(config-cfm)# domain Domain_One level 1 id string D1
Creates and names a container for all domain configurations and
enters the CFM domain configuration mode.
The level must be specified.
The
id is the maintenance domain identifier (MDID) and
is used as the first part of the maintenance association identifier (MAID) in
CFM frames. If the MDID is not specified, the domain name is used as the MDID
by default.
RP/0/RP0/CPU0:router(config-cfm-dmn)# service Bridge_Service bridge group BD1 bridge-domain B1
Configures and associates a service with the domain and enters
CFM domain service configuration mode. You can specify that the service is used
only for down MEPs, or associate the service with a bridge domain or xconnect
where MIPs and up MEPs will be created.
RP/0/RP0/CPU0:router(config-cfm)# domain Domain_One level 1 id string D1
Creates and names a container for all domain configurations and
enters the CFM domain configuration mode.
The level must be specified.
The
id is the maintenance domain identifier (MDID) and
is used as the first part of the maintenance association identifier (MAID) in
CFM frames. If the MDID is not specified, the domain name is used as the MDID
by default.
RP/0/RP0/CPU0:router(config-cfm-dmn)# service Bridge_Service bridge group BD1 bridge-domain B1
Configures and associates a service with the domain and enters
CFM domain service configuration mode. You can specify that the service is used
only for down MEPs, or associate the service with a bridge domain or xconnect
where MIPs and up MEPs will be created.
Type of Ethernet interface on which you want to create a MEP.
Enter
HundredGigE, TenGigE, or
Bundle-Ether
and the physical interface or virtual interface
followed by the subinterface path ID.
Naming convention is interface-path-id.subinterface. The period in front of the subinterface value is required as part of the notation.
Step 4
vrf vrf-name
Example:
RP/0/RP0/CPU0:router(config-if)# vrf vrf_A
Configures a VRF instance and enters VRF configuration mode.
RP/0/RP0/CPU0:router(config-if-cfm)# mep domain Dm1 service Sv1 mep-id 1
Creates a maintenance end point (MEP) on an interface and enters
interface CFM MEP configuration mode.
Step 8
coscos
Example:
RP/0/RP0/CPU0:router(config-if-cfm-mep)# cos 7
(Optional) Configures the class of service (CoS) (from 0 to 7)
for all CFM packets generated by the MEP on an interface. If not configured,
the CoS is inherited from the Ethernet interface.
Note
For Ethernet interfaces, the CoS is carried as a field in the VLAN tag. Therefore, CoS only applies to interfaces where packets
are sent with VLAN tags. If the cos (CFM) command is executed for a MEP on an interface that does not have a VLAN encapsulation configured, it will be ignored.
Step 9
end or
commit
Example:
RP/0/RP0/CPU0:router(config-if-cfm-mep)# commit
Saves configuration changes.
When you use the
end command, the system prompts you to commit
changes:
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:
Entering
yes saves configuration changes to the running configuration
file, exits the configuration session, and returns the router to EXEC mode.
Entering
no exits the configuration session and returns the
router to EXEC mode without committing the configuration changes.
Entering
cancel leaves the router in the current
configuration session without exiting or committing the configuration changes.
Use the
commit command to save the configuration changes
to the running configuration file and remain within the configuration session.
Configuring Y.1731 AIS
This section has the following step procedures:
Configuring AIS in a
CFM Domain Service
Use the following procedure to configure Alarm Indication Signal
(AIS) transmission for a CFM domain service and configure AIS logging.
RP/0/RP0/CPU0:router(config-cfm-dmn)# service S2 bridge group BG1 bridge-domain BD2
Specifies the service, bridge group, and bridge domain.
Step 5
tags
number
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# tags 1
Specifies the number of tags in CFM packets. Currently, the only
valid value is 1.
Step 6
end or
commit
Example:
RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# commit
Saves configuration changes.
When you issue the
end command, the system prompts you to commit
changes:
Uncommitted changes found, commit them before exiting(yes/no/cancel)?
[cancel]:
Entering
yes saves configuration changes to the running configuration
file, exits the configuration session, and returns the router to EXEC mode.
Entering
no exits the configuration session and returns the
router to EXEC mode without committing the configuration changes.
Entering
cancel leaves the router in the current
configuration session without exiting or committing the configuration changes.
Use the
commit command to save the configuration changes
to the running configuration file and remain within the configuration session.
Verifying the CFM Configuration
To verify the CFM configuration, use one or more of the following commands:
show ethernet cfm configuration-errors [domaindomain-name] [interfaceinterface-path-id ]
Displays information about errors that are preventing configured CFM operations from becoming active, as well as any warnings
that have occurred.
show ethernet cfm local maintenance-points domainname [servicename] | interfacetypeinterface-path-id] [mep | mip]
Displays a list of local maintenance points.
Note
After you configure CFM, the error message, cfmd[317]: %L2-CFM-5-CCM_ERROR_CCMS_MISSED : Some received CCMs have not been counted by the CCM error counters, may display. This error message does not have any functional impact and does not require any action from you.
Troubleshooting
Tips
To troubleshoot problems within the CFM network, perform these
steps:
SUMMARY STEPS
To verify connectivity to a problematic MEP, use the
ping ethernet
cfm command as shown in this example:
If the results of the
ping ethernet
cfm command show a problem with connectivity to the peer MEP, use
the
traceroute ethernet
cfm command to help further isolate the location of the problem
as shown in the following example:
DETAILED STEPS
Step 1
To verify connectivity to a problematic MEP, use the
ping ethernet
cfm command as shown in this example:
RP/0/RP0/CPU0:router# ping ethernet cfm domain D1 service S1 mep-id 16 sourceinterface TenGigE 0/0/0/1
Type escape sequence to abort.
Sending 5 CFM Loopbacks, timeout is 2 seconds -
Domain foo (level 2), Service foo
Source: MEP ID 1, interface TenGigE0/0/0/1
Target: 0001.0002.0003 (MEP ID 16):
Running (5s) ...
Success rate is 60.0 percent (3/5), round-trip min/avg/max = 1251/1349/1402 ms
Out-of-sequence: 0.0 percent (0/3)
Bad data: 0.0 percent (0/3)
Received packet rate: 1.4 pps
Step 2
If the results of the
ping ethernet
cfm command show a problem with connectivity to the peer MEP, use
the
traceroute ethernet
cfm command to help further isolate the location of the problem
as shown in the following example:
RP/0/RP0/CPU0:router# traceroute ethernet cfm domain D1 service S1 mep-id 16 source interface TenGigE 0/0/0/2
Traceroutes in domain D1 (level 4), service S1
Source: MEP-ID 1, interface TenGigE0/0/0/2
================================================================================
Traceroute at 2009-05-18 12:09:10 to 0001.0203.0402,
TTL 64, Trans ID 2:
Hop Hostname/Last Ingress MAC/name Egress MAC/Name Relay
--- ------------------------ ---------------------- ---------------------- -----
1 ios 0001.0203.0400 [Down] FDB
0000-0001.0203.0400 TenGigE0/0/0/2
2 abc 0001.0203.0401 [Ok] FDB
ios Not present
3 bcd 0001.0203.0402 [Ok] Hit
abc TenGigE0/0
Replies dropped: 0
If the target was a MEP, verify that the last hop shows “Hit” in
the Relay field to confirm connectivity to the peer MEP.
If the Relay field contains “MPDB” for any of the hops, then the
target MAC address was not found in the bridge MAC learning table at that hop,
and the result is relying on CCM learning. This result can occur under normal
conditions, but it can also indicate a problem. If you used the
ping
ethernet cfm command before using the
traceroute ethernet cfm command, then the MAC
address should have been learned. If “MPDB” is appearing in that case, then
this indicates a problem at that point in the network.
Unidirectional Link Detection Protocol
Unidirectional Link Detection (UDLD) is a single-hop physical link protocol for monitoring an ethernet link, including both
point-to-point and shared media links. This is a Cisco-proprietary protocol to detect link problems, which are not detected
at the physical link layer. This protocol is specifically targeted at possible wiring errors, when using unbundled fiber links,
where there can be a mismatch between the transmitting and receiving connections of a port.
UDLD Operation
UDLD works by exchanging protocol packets between the neighboring devices. In order for UDLD to work, both devices on the
link must support UDLD and have it enabled on respective ports.
UDLD sends an initial PROBE message on the ports where it is configured. Once UDLD receives a PROBE message, it sends periodic
ECHO (hello) messages. Both messages identify the sender and its port, and also contain some information about the operating
parameters of the protocol on that port. They also contain the device and port identifiers on the port for any neighbor devices
that the local device has heard from. Similarly, each device gets to know where it is connected and where its neighbors are
connected. This information can then be used to detect faults and miswiring conditions.
The protocol operates an aging mechanism where information from neighbors that is not periodically refreshed is eventually
timed out. This mechanism can also be used to detect fault.
A FLUSH message is used to indicate that UDLD is disabled on a port, which causes the peers to remove the local device from
their neighbor cache to prevent a time out.
If a problem is detected, UDLD disables the affected interface and also notifies the user. This is to avoid further network
problems beyond traffic loss, such as loops which are not detected or prevented by Spanning Tree Protocol (STP).
Types of Fault Detection
UDLD can detect these types of faults:
Transmit faults — These are cases where there is a failure in transmitting packets from the local port to the peer device,
but packets are being received from the peer. These faults are caused by failure of the physical link (where notification
at layer 1 of unidirectional link faults is not supported by the media) as well as packet path faults on the local or peer
device.
Miswiring faults — These are cases where the receiving and transmitting sides of a port on the local device are connected
to different peer ports (on the same device or on different devices). This can occur when using unbundled fibers to connect
fiber optic ports.
Loopback faults — These are cases where the receiving and transmitting sides of a port are connected to each other, creating
a loopback condition. This can be an intentional mode of operation, for certain types of testing, but UDLD must not be used
in these cases.
Receive faults — The protocol includes a heartbeat signal that is transmitted at a negotiated periodic interval to the peer
device. Missed heartbeats can therefore be used to detect failures on the receiving side of the link (where they do not result
in interface state changes). These could be caused by a unidirectional link with a failure only affecting the receiving side,
or by a link which has developed a bidirectional fault. This detection depends on reliable, regular packet transmission by
the peer device. For this reason, the UDLD protocol has two (configurable) modes of operation which determine the behavior
on a heartbeat timeout. These modes are described in the section UDLD Modes of Operation.
UDLD Modes of Operation
UDLD can operate in these modes:
Normal mode: In this mode, if a Receive Fault is detected, the user is informed and no further action is taken.
Aggressive mode: In this mode, if a Receive Fault is detected, the user is informed and the affected port is disabled.
UDLD Aging Mechanism
This is a scenario that happens in a Receive Fault condition. Aging of UDLD information happens when the port that runs UDLD does not receive UDLD packets from the neighbor
port for a duration of the hold time. The hold time for the port is dictated by the remote port and depends on the message
interval at the remote side. The shorter the message interval, the shorter is the hold time and the faster the detection of
the fault. The hold time is three times the message interval in Cisco IOS XR Software.
UDLD information can age out due to the high error rate on the port caused by a physical issue or duplex mismatch. Packet
drops due to age out does not mean that the link is unidirectional. UDLD in normal mode does not disable such link.
It is important to choose the right message interval in order to ensure proper detection time. The message interval should
be fast enough to detect the unidirectional link before the forwarding loop is created. The default message interval is 60
seconds. The detection time is equal to approximately three times the message interval. So, when using default UDLD timers,
UDLD does not timeout the link faster than the STP aging time.
State Machines
UDLD uses two types of finite state machines (FSMs), generally referred as state machines. The Main FSM deals with all the phases of operation of the protocol while the Detection FSM handles only the phases that determine the status of a port.
Main FSM
The Main FSM can be in one of these states:
Init: Protocol is initializing.
UDLD inactive: Port is down or UDLD is disabled.
Linkup: Port is up and running, and UDLD is in the process of detecting a neighbor.
Detection: A hello message from a new neighbor is received and the Detection FSM determines the status of the port.
Advertisement: The Detection FSM concludes that the port is operating correctly, periodic hello messages will continue to be sent and monitored
from neighbors.
Port shutdown: The Detection FSM detected a fault, or all neighbors were timed out in Aggressive mode, and as a result, the port is disabled.
Detection FSM
The Detection FSM can be in one of these states:
Unknown: Detection has not yet been performed or UDLD has been disabled.
Unidirectional detected: A unidirectional link condition has been detected because a neighbor does not see the local device. The port will be disabled.
Tx/Rx loop: A loopback condition has been detected by receiving a TLV with the ports own identifiers. The port will be disabled.
Neighbor mismatch: A miswiring condition has been detected in which a neighbor can identify other devices than those the local device can see.
The port will be disabled.
Bidirectional detected: UDLD hello messages are exchanged successfully in both directions. The port is operating correctly.
Configuration Examples for Ethernet OAM
This section provides the following configuration examples:
Configuration Examples for Ethernet CFM
This section includes the following examples:
Ethernet CFM Domain Configuration: Example
This example shows how to configure a basic domain for Ethernet CFM:
These examples show how to verify the configuration of Ethernet
Connectivity Fault Management (CFM):
Example
1
This example shows how to display all the maintenance points
that have been created on an interface:
RP/0/RP0/CPU0:router# show ethernet cfm local maintenance-points
Domain/Level Service Interface Type ID MAC
-------------------- ------------------- ----------------- ------ ---- --------
fig/5 bay Gi0/10/0/12 Dn MEP 2 44:55:66
fig/5 bay Gi0/0/1/0 MIP 55:66:77
fred/3 barney Gi0/1/0/0 Dn MEP 5 66:77:88!
Example
2
This example shows how to display all the CFM configuration
errors on all domains:
RP/0/RP0/CPU0:router# show ethernet cfm configuration-errors
Domain fig (level 5), Service bay
* MIP creation configured using bridge-domain blort, but bridge-domain blort does not exist.
* An Up MEP is configured for this domain on interface TenGigE0/0/0/3 and an Up MEP is also configured for domain blort, which is at the same level (5).
* A MEP is configured on interface TenGigE0/0/0/1 for this domain/service, which has CC interval 100ms, but the lowest interval supported on that interface is 1s
Example
3
This example shows how to display operational state for local
maintenance end points (MEPs):
RP/0/RP0/CPU0:router# show ethernet cfm local meps
A - AIS received I - Wrong interval
R - Remote Defect received V - Wrong Level
L - Loop (our MAC received) T - Timed out (archived)
C - Config (our ID received) M - Missing (cross-check)
X - Cross-connect (wrong MAID) U - Unexpected (cross-check)
P - Peer port down
Domain foo (level 6), Service bar
ID Interface (State) Dir MEPs/Err RD Defects AIS
----- ------------------------ --- -------- -- ------- ---
100 Gi1/1/0/1 (Up) Up 0/0 N A L7
Domain fred (level 5), Service barney
ID Interface (State) Dir MEPs/Err RD Defects AIS
----- ------------------------ --- -------- -- ------- ---
2 Gi0/1/0/0 (Up) Up 3/2 Y RPC L6
Domain foo (level 6), Service bar
ID Interface (State) Dir MEPs/Err RD Defects AIS
----- ------------------------ --- -------- -- ------- ---
100 Gi1/1/0/1 (Up) Up 0/0 N A
Domain fred (level 5), Service barney
ID Interface (State) Dir MEPs/Err RD Defects AIS
----- ------------------------ --- -------- -- ------- ---
2 Gi0/1/0/0 (Up) Up 3/2 Y RPC
Example
4
This example shows how to display operational state of other
maintenance end points (MEPs) detected by a local MEP:
RP/0/RP0/CPU0:router# show ethernet cfm peer meps
Flags:
> - Ok I - Wrong interval
R - Remote Defect received V - Wrong level
L - Loop (our MAC received) T - Timed out
C - Config (our ID received) M - Missing (cross-check)
X - Cross-connect (wrong MAID) U - Unexpected (cross-check)
Domain fred (level 7), Service barney
Down MEP on TenGigE0/0/0/1, MEP-ID 2
================================================================================
St ID MAC address Port Up/Downtime CcmRcvd SeqErr RDI Error
-- ----- -------------- ------- ----------- --------- ------ ----- -----
> 1 0011.2233.4455 Up 00:00:01 1234 0 0 0
R> 4 4455.6677.8899 Up 1d 03:04 3456 0 234 0
L 2 1122.3344.5566 Up 3w 1d 6h 3254 0 0 3254
C 2 7788.9900.1122 Test 00:13 2345 6 20 2345
X 3 2233.4455.6677 Up 00:23 30 0 0 30
I 3 3344.5566.7788 Down 00:34 12345 0 300 1234
V 3 8899.0011.2233 Blocked 00:35 45 0 0 45
T 5 5566.7788.9900 00:56 20 0 0 0
M 6 0 0 0 0
U> 7 6677.8899.0011 Up 00:02 456 0 0 0
Domain fred (level 7), Service fig
Down MEP on TenGigE0/0/0/12, MEP-ID 3
================================================================================
St ID MAC address Port Up/Downtime CcmRcvd SeqErr RDI Error
-- ----- -------------- ------- ----------- -------- ------ ----- -----
> 1 9900.1122.3344 Up 03:45 4321 0 0 0
Example
5
This example shows how to display operational state of other
maintenance end points (MEPs) detected by a local MEP with details:
RP/0/RP0/CPU0:router# show ethernet cfm peer meps detail
Domain dom3 (level 5), Service ser3
Down MEP on TenGigE0/0/0/1 MEP-ID 1
================================================================================
Peer MEP-ID 10, MAC 0001.0203.0403
CFM state: Wrong level, for 00:01:34
Port state: Up
CCM defects detected: V - Wrong Level
CCMs received: 5
Out-of-sequence: 0
Remote Defect received: 5
Wrong Level: 0
Cross-connect (wrong MAID): 0
Wrong Interval: 5
Loop (our MAC received): 0
Config (our ID received): 0
Last CCM received 00:00:06 ago:
Level: 4, Version: 0, Interval: 1min
Sequence number: 5, MEP-ID: 10
MAID: String: dom3, String: ser3
Port status: Up, Interface status: Up
Domain dom4 (level 2), Service ser4
Down MEP on TenGigE0/0/0/2 MEP-ID 1
================================================================================
Peer MEP-ID 20, MAC 0001.0203.0402
CFM state: Ok, for 00:00:04
Port state: Up
CCMs received: 7
Out-of-sequence: 1
Remote Defect received: 0
Wrong Level: 0
Cross-connect (wrong MAID): 0
Wrong Interval: 0
Loop (our MAC received): 0
Config (our ID received): 0
Last CCM received 00:00:04 ago:
Level: 2, Version: 0, Interval: 10s
Sequence number: 1, MEP-ID: 20
MAID: String: dom4, String: ser4
Chassis ID: Local: ios; Management address: 'Not specified'
Port status: Up, Interface status: Up
Peer MEP-ID 21, MAC 0001.0203.0403
CFM state: Ok, for 00:00:05
Port state: Up
CCMs received: 6
Out-of-sequence: 0
Remote Defect received: 0
Wrong Level: 0
Cross-connect (wrong MAID): 0
Wrong Interval: 0
Loop (our MAC received): 0
Config (our ID received): 0
Last CCM received 00:00:05 ago:
Level: 2, Version: 0, Interval: 10s
Sequence number: 1, MEP-ID: 21
MAID: String: dom4, String: ser4
Port status: Up, Interface status: Up
Peer MEP-ID 601, MAC 0001.0203.0402
CFM state: Timed Out (Standby), for 00:15:14, RDI received
Port state: Down
CCM defects detected: Defects below ignored on local standby MEP
I - Wrong Interval
R - Remote Defect received
T - Timed Out
P - Peer port down
CCMs received: 2
Out-of-sequence: 0
Remote Defect received: 2
Wrong Level: 0
Wrong Interval: 2
Loop (our MAC received): 0
Config (our ID received): 0
Last CCM received 00:15:49 ago:
Level: 2, Version: 0, Interval: 10s
Sequence number: 1, MEP-ID: 600
MAID: DNS-like: dom5, String: ser5
Chassis ID: Local: ios; Management address: 'Not specified'
Port status: Up, Interface status: Down
AIS for CFM
Configuration: Examples
Example
1
This example shows how to configure Alarm Indication Signal
(AIS) transmission for a CFM domain service:
RP/0/RP0/CPU0:router# configure RP/0/RP0/CPU0:router(config)# ethernet cfmRP/0/RP0/CPU0:router(config-cfm)# domain D1 level 1 RP/0/RP0/CPU0:router(config-cfm-dmn)# service S1 bridge group BG1 bridge-domain BD2 RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# ais transmission interval 1m cos 7 RP/0/RP0/CPU0:routerconfigure RP/0/RP0/CPU0:router(config)# ethernet cfmRP/0/RP0/CPU0:router(config-cfm)# domain D1 level 1 RP/0/RP0/CPU0:router(config-cfm-dmn)# service Cross_Connect_1 xconnect group XG1 p2p X1RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# ais transmission interval 1m cos 7
Example
2
This example shows how to configure AIS logging for a
Connectivity Fault Management (CFM) domain service to indicate when AIS or LCK
packets are received:
RP/0/RP0/CPU0:router# configure RP/0/RP0/CPU0:router(config)# ethernet cfmRP/0/RP0/CPU0:router(config-cfm)# domain D1 level 1RP/0/RP0/CPU0:router(config-cfm-dmn)# service S2 bridge group BG1 bridge-domain BD2 RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# log aisRP/0/RP0/CPU0:routerconfigure RP/0/RP0/CPU0:router(config)# ethernet cfmRP/0/RP0/CPU0:router(config-cfm)# domain D1 level 1 RP/0/RP0/CPU0:router(config-cfm-dmn)# service Cross_Connect_1 xconnect group XG1 p2p X1RP/0/RP0/CPU0:router(config-cfm-dmn-svc)# log ais
This example shows how to configure AIS transmission on a CFM
interface.
RP/0/RP0/CPU0:router# configure RP/0/RP0/CPU0:router(config)# interface TenGigE 0/1/0/2 RP/0/RP0/CPU0:router(config-if)# ethernet cfm RP/0/RP0/CPU0:router(config-if-cfm)# ais transmission up interval 1m cos 7
AIS for CFM Show Commands: Examples
This section includes the following examples:
show ethernet cfm
interfaces ais Command: Example
This example shows how to display the information published in
the Interface AIS table:
RP/0/RP0/CPU0:router# show ethernet cfm interfaces ais
Defects (from at least one peer MEP):
A - AIS received I - Wrong interval
R - Remote Defect received V - Wrong Level
L - Loop (our MAC received) T - Timed out (archived)
C - Config (our ID received) M - Missing (cross-check)
X - Cross-connect (wrong MAID) U - Unexpected (cross-check)
P - Peer port down D - Local port down
Trigger Transmission
AIS --------- Via ---------------------------
Interface (State) Dir L Defects Levels L Int Last started Packets
------------------------ --- - ------- ------- - --- ------------ --------
TenGigE0/0/0/0 (Up) Dn 5 RPC 6 7 1s 01:32:56 ago 5576
TenGigE0/0/0/0 (Up) Up 0 M 2,3 5 1s 00:16:23 ago 983
TenGigE0/0/0/1 (Dn) Up D 7 60s 01:02:44 ago 3764
TenGigE0/0/0/2 (Up) Dn 0 RX 1!
show ethernet cfm
local meps Command: Examples
Example 1:
Default
This example shows how to display statistics for local
maintenance end points (MEPs):
RP/0/RP0/CPU0:router# show ethernet cfm local meps
A - AIS received I - Wrong interval
R - Remote Defect received V - Wrong Level
L - Loop (our MAC received) T - Timed out (archived)
C - Config (our ID received) M - Missing (cross-check)
X - Cross-connect (wrong MAID) U - Unexpected (cross-check)
P - Peer port down
Domain foo (level 6), Service bar
ID Interface (State) Dir MEPs/Err RD Defects AIS
----- ------------------------ --- -------- -- ------- ---
100 Gi1/1/0/1 (Up) Up 0/0 N A 7
Domain fred (level 5), Service barney
ID Interface (State) Dir MEPs/Err RD Defects AIS
----- ------------------------ --- -------- -- ------- ---
2 Gi0/1/0/0 (Up) Up 3/2 Y RPC 6
Example 2:
Domain Service
This example shows how to display statistics for MEPs in a
domain service:
RP/0/RP0/CPU0:router# show ethernet cfm local meps domain foo service bar detail
Domain foo (level 6), Service bar
Down MEP on TenGigE0/0/0/1, MEP-ID 100
================================================================================
Interface state: Up MAC address: 1122.3344.5566
Peer MEPs: 0 up, 0 with errors, 0 timed out (archived)
CCM generation enabled: No
AIS generation enabled: Yes (level: 7, interval: 1s)
Sending AIS: Yes (started 01:32:56 ago)
Receiving AIS: Yes (from lower MEP, started 01:32:56 ago)
Domain fred (level 5), Service barney
Down MEP on TenGigE0/0/0/1, MEP-ID 2
================================================================================
Interface state: Up MAC address: 1122.3344.5566
Peer MEPs: 3 up, 2 with errors, 0 timed out (archived)
Cross-check defects: 0 missing, 0 unexpected
CCM generation enabled: Yes (Remote Defect detected: Yes)
CCM defects detected: R - Remote Defect received
P - Peer port down
C - Config (our ID received)
AIS generation enabled: Yes (level: 6, interval: 1s)
Sending AIS: Yes (to higher MEP, started 01:32:56 ago)
Receiving AIS: No
Example 4:
Detail
This example shows how to display detailed statistics for MEPs
in a domain service:
RP/0/RP0/CPU0:router# show ethernet cfm local meps detail
Domain foo (level 6), Service bar
Down MEP on TenGigE0/0/0/1, MEP-ID 100
================================================================================
Interface state: Up MAC address: 1122.3344.5566
Peer MEPs: 0 up, 0 with errors, 0 timed out (archived)
CCM generation enabled: No
AIS generation enabled: Yes (level: 7, interval: 1s)
Sending AIS: Yes (started 01:32:56 ago)
Receiving AIS: Yes (from lower MEP, started 01:32:56 ago)
Domain fred (level 5), Service barney
Down MEP on TenGigE0/0/0/1, MEP-ID 2
================================================================================
Interface state: Up MAC address: 1122.3344.5566
Peer MEPs: 3 up, 2 with errors, 0 timed out (archived)
Cross-check defects: 0 missing, 0 unexpected
CCM generation enabled: Yes (Remote Defect detected: Yes)
CCM defects detected: R - Remote Defect received
P - Peer port down
C - Config (our ID received)
AIS generation enabled: Yes (level: 6, interval: 1s)
Sending AIS: Yes (to higher MEP, started 01:32:56 ago)
Receiving AIS: No
show ethernet cfm
local meps detail Command: Example
Use the
show ethernet cfm local meps
detail command to display MEP-related EFD status information.
This example shows that EFD is triggered for MEP-ID 100:
RP/0/RP0/CPU0:router# show ethernet cfm local meps detail
Domain foo (level 6), Service bar
Down MEP on TenGigE0/0/0/1, MEP-ID 100
================================================================================
Interface state: Up MAC address: 1122.3344.5566
Peer MEPs: 0 up, 0 with errors, 0 timed out (archived)
Cross-check errors: 2 missing, 0 unexpected
CCM generation enabled: No
AIS generation enabled: Yes (level: 7, interval: 1s)
Sending AIS: Yes (started 01:32:56 ago)
Receiving AIS: Yes (from lower MEP, started 01:32:56 ago)
EFD triggered: Yes
Domain fred (level 5), Service barney
Down MEP on TenGigE0/0/0/1, MEP-ID 2
================================================================================
Interface state: Up MAC address: 1122.3344.5566
Peer MEPs: 3 up, 0 with errors, 0 timed out (archived)
Cross-check errors: 0 missing, 0 unexpected
CCM generation enabled: Yes (Remote Defect detected: No)
AIS generation enabled: Yes (level: 6, interval: 1s)
Sending AIS: No
Receiving AIS: No
EFD triggered: No
Note
You can also verify that EFD has been triggered on an interface
using the
show interfaces
and
show interfaces
brief commands. When an EFD trigger has occurred, these commands
will show the interface status as
up and the line protocol state as
down.
Feedback