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This module provides the conceptual and configuration information for Point to Point Layer 2 services on Cisco IOS XR software.
 Note |
The Point to Point Layer 2 services are also called as MPLS Layer 2 VPNs. |
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Release |
Modification |
|---|---|
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Release 5.2.1 |
The point to point layer 2 services were introduced. |
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Release 5.2.3 |
Support was added for QinQ mode, Inter-AS mode, and GTP load balancing. |
You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command.
If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
To implement Point to Point Layer 2 Services, you should understand these concepts:
Layer 2 VPN (L2VPN) emulates the behavior of a LAN across an IP or MPLS-enabled IP network allowing Ethernet devices to communicate with each other as they would when connected to a common LAN segment.
As Internet service providers (ISPs) look to replace their Asynchronous Transfer Mode (ATM) infrastructures with an IP infrastructure, there is a need for to provide standard methods of using an IP infrastructure to provide a serviceable L2 interface to customers; specifically, to provide standard ways of using an IP infrastructure to provide virtual circuits between pairs of customer sites.
Building a L2VPN system requires coordination between the ISP and the customer. The ISP provides L2 connectivity; the customer builds a network using data link resources obtained from the ISP. In an L2VPN service, the ISP does not require information about a the customer's network topology, policies, routing information, point-to-point links, or network point-to-point links from other ISPs.
The ISP requires provider edge (PE) routers with the following capabilities:
Virtual Circuit Connection Verification (VCCV) is an L2VPN Operations, Administration, and Maintenance (OAM) feature that allows network operators to run IP-based provider edge-to-provider edge (PE-to-PE) keepalive protocol across a specified pseudowire to ensure that the pseudowire data path forwarding does not contain any faults. The disposition PE receives VCCV packets on a control channel, which is associated with the specified pseudowire. The control channel type and connectivity verification type, which are used for VCCV, are negotiated when the pseudowire is established between the PEs for each direction.
Two types of packets can arrive at the disposition egress:
Type 1—Specifies normal Ethernet-over-MPLS (EoMPLS) data packets.
Type 2—Specifies VCCV packets.
Cisco NCS 6000 Series Router supports Label Switched Path (LSP) VCCV Type 1, which uses an inband control word if enabled during signaling. The VCCV echo reply is sent as IPv4 that is the reply mode in IPv4. The reply is forwarded as IP, MPLS, or a combination of both.
VCCV pings counters that are counted in MPLS forwarding on the egress side. However, on the ingress side, they are sourced by the route processor and do not count as MPLS forwarding counters.
Ethernet-over-MPLS (EoMPLS) provides a tunneling mechanism for Ethernet traffic through an MPLS-enabled L3 core and encapsulates Ethernet protocol data units (PDUs) inside MPLS packets (using label stacking) to forward them across the MPLS network.
EoMPLS features are described in these subsections:
In Ethernet port mode, both ends of a pseudowire are connected to Ethernet ports. In this mode, the port is tunneled over the pseudowire or, using local switching (also known as an attachment circuit-to-attachment circuit cross-connect) switches packets or frames from one attachment circuit (AC) to another AC attached to the same PE node.
The following figure provides an example of Ethernet port mode.
Ethernet remote port shutdown provides a mechanism for the detection and propagation of remote link failure for port mode EoMPLS on a Cisco NCS 6000 Series Router line card. This lets a service provider edge router on the local end of an Ethernet-over-MPLS (EoMPLS) pseudowire detect a cross-connect or remote link failure and cause the shutdown of the Ethernet port on the local customer edge router. Shutting down the Ethernet port on the local customer edge router prevents or mitigates a condition where that router would otherwise lose data by forwarding traffic continuously to the remote failed link, especially if the link were configured as a static IP route (see following figure)..
To enable this functionality, see the l2transport propagate command in MPLS Command Reference for Cisco NCS 6000 Series Routers.
In VLAN mode, each VLAN on a customer-end to provider-end link can be configured as a separate L2VPN connection using virtual connection (VC) type 4 or VC type 5. VC type 5 is the default mode.
As illustrated in the following figure, the Ethernet PE associates an internal VLAN-tag to the Ethernet port for switching the traffic internally from the ingress port to the pseudowire; however, before moving traffic into the pseudowire, it removes the internal VLAN tag.
At the egress VLAN PE, the PE associates a VLAN tag to the frames coming off of the pseudowire and after switching the traffic internally, it sends out the traffic on an Ethernet trunk port.
Note |
Because the port is in trunk mode, the VLAN PE doesn't remove the VLAN tag and forwards the frames through the port with the added tag. |
Inter-AS is a peer-to-peer type model that allows extension of VPNs through multiple provider or multi-domain networks. This lets service providers peer up with one another to offer end-to-end VPN connectivity over extended geographical locations.
EoMPLS support can assume a single AS topology where the pseudowire connecting the PE routers at the two ends of the point-to-point EoMPLS cross-connects resides in the same autonomous system; or multiple AS topologies in which PE routers can reside on two different ASs using iBGP and eBGP peering.
The following figure illustrates MPLS over Inter-AS with a basic double AS topology with iBGP/LDP in each AS.
QinQ is an extension of 802.1Q for specifying multiple 802.1Q tags (IEEE 802.1QinQ VLAN Tag stacking). Layer 3 VPN service termination and L2VPN service transport are enabled over QinQ sub-interfaces.
The Cisco NCS 6000 Series Routers implement the Layer 2 tunneling or Layer 3 forwarding depending on the subinterface configuration at provider edge routers. This function only supports up to two QinQ tags on the SPA and fixed PLIM:
Layer 2 QinQ VLANs in L2VPN attachment circuit: QinQ L2VPN attachment circuits are configured under the Layer 2 transport subinterfaces for point-to-point EoMPLS based cross-connects using virtual circuit type 4 pseudowires and point-to-point local-switching-based cross-connects including full interworking support of QinQ with 802.1q VLANs and port mode.
Layer 3 QinQ VLANs: Used as a Layer 3 termination point, both VLANs are removed at the ingress provider edge and added back at the remote provider edge as the frame is forwarded.
Layer 3 services over QinQ include:
IPv4 unicast and multicast
IPv6 unicast and multicast
MPLS
Note |
The Cisco NCS 6000 Series Router does not support: bundle attachment circuits and Hot Standby Router Protocol (HSRP) or Virtual Router Redundancy Protocol (VRRP) on QinQ subinterfaces. |
In QinQ mode, each CE VLAN is carried into an SP VLAN. QinQ mode should use VC type 5, but VC type 4 is also supported. On each Ethernet PE, you must configure both the inner (CE VLAN) and outer (SP VLAN).
The following figure illustrates QinQ using VC type 4.
L2VPN uses control planes in both route processors and line cards, as well as forwarding plane elements in the line cards.
Note |
The l2tp_mgr process does not support high availability. |
The availability of L2VPN meets these requirements:
A control plane failure in either the route processor or the line card will not affect the circuit forwarding path.
The router processor control plane supports failover without affecting the line card control and forwarding planes.
L2VPN integrates with existing Label Distribution Protocol (LDP) graceful restart mechanism.
Preferred tunnel path functionality lets you map pseudowires to specific traffic-engineering tunnels. Attachment circuits are cross-connected to specific MPLS traffic engineering tunnel interfaces instead of remote PE router IP addresses (reachable using IGP or LDP). Using preferred tunnel path, it is always assumed that the traffic engineering tunnel that transports the L2 traffic runs between the two PE routers (that is, its head starts at the imposition PE router and its tail terminates on the disposition PE router).
Note |
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Pseudowire redundancy allows you to configure your network to detect a failure in the network and reroute the Layer 2 service to another endpoint that can continue to provide service. This feature provides the ability to recover from a failure of either the remote provider edge (PE) router or the link between the PE and customer edge (CE) routers.
L2VPNs can provide pseudowire resiliency through their routing protocols. When connectivity between end-to-end PE routers fails, an alternative path to the directed LDP session and the user data takes over. However, there are some parts of the network in which this rerouting mechanism does not protect against interruptions in service.
Pseudowire redundancy enables you to set up backup pseudowires. You can configure the network with redundant pseudowires and redundant network elements.
Prior to the failure of the primary pseudowire, the ability to switch traffic to the backup pseudowire is used to handle a planned pseudowire outage, such as router maintenance.
Note |
Pseudowire redundancy is provided only for point-to-point Virtual Private Wire Service (VPWS) pseudowires. |
Flow Aware Transport Pseudowires (FAT PW) are used to load-balance traffic in the core when equal cost multipaths (ECMP) are used. The flow, in this context, refers to a sequence of packets that have the same source and destination pair. The packets are transported from a source provider edge (PE) to a destination PE.
The following figure shows a FAT PW with two flows distributing over ECMPs and bundle links.
The MPLS labels add an additional label to the stack, called the flow label, which contains the flow information of a virtual circuit (VC). A flow label is a unique identifier that distinguishes a flow within the PW, and is derived from the IP payload of a packet. The flow label contains the end of label stack (EOS) bit set and inserted after the VC label and before the control word (if any). The ingress PE calculates and forwards the flow label. The FAT PW configuration enables the flow label. The egress PE discards the flow label such that no decisions are taken based on that label.
All core routers perform load balancing based on the flow-label in the FAT PW. Therefore, it is possible to distribute flows over ECMPs and link bundles.
You cannot send MPLS OAM ping traffic over a FAT PW, since there is no flow label support for MPLS OAM.
The L2VPN Nonstop Routing (NSR) feature avoids label distribution path (LDP) sessions from flapping on events such as process failures (crash) and route processor failover (RP FO). NSR on process failure (crash) is supported by performing RP FO, if you have enabled NSR using NSR process failure switchover.
NSR enables the router (where failure has occurred) to maintain the control plane states without a graceful restart (GR). NSR, by definition, does not require any protocol extension and typically uses Stateful Switch Over (SSO) to maintain it’s control plane states.
Note |
NSR is enabled by default for L2VPN on Cisco IOS XR 64 bit operating system. You cannot configure the nsr command under L2VPN configuration submode. |
This section describes the tasks required to implement Point to Point Layer 2 Services:
Perform this task to configure an interface or a connection for Point to Point Layer 2 Services.
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Step 1 |
configure Example:Enters the XR Config mode. |
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Step 2 |
interface type interface-path-id Example:Enters interface configuration mode and configures an interface. |
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Step 3 |
l2transport Example:Enables L2 transport on the selected interface. |
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Step 4 |
exit Example:Exits the current configuration mode. |
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Step 5 |
interface type interface-path-id.subinterface l2transport Example:Enters subinterface configuration mode and configures the subinterface as a layer 2 interface. |
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Step 6 |
encapsulation dot1q vlan-id Example:Assigns native VLAN ID to an interface trunking 802.1Q VLAN traffic. |
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Step 7 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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Note |
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Note |
Static pseudowire connections do not use LDP for signaling. |
Perform this task to configure static point-to-point cross-connects.
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Step 1 |
configure Example:Enters the XR Config mode. |
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Step 2 |
l2vpn Example:Enters L2VPN configuration mode. |
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Step 3 |
xconnect group group-name Example:Enters the name of the cross-connect group. |
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Step 4 |
p2p xconnect-name Example:Enters a name for the point-to-point cross-connect. |
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Step 5 |
interface type interface-path-id Example:Specifies the interface type and instance. |
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Step 6 |
neighbor ip-address pw-id pseudowire-id Example:Configures the pseudowire segment for the cross-connect. Optionally, you can disable the control word or set the transport-type to Ethernet or VLAN. |
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Step 7 |
mpls static label local { value } remote { value } Example:Configures local and remote label ID values. |
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Step 8 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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Step 9 |
show l2vpn xconnect group group name Example:Displays the name of the Point-to-Point cross-connect group you created. |
Perform this task to configure dynamic point-to-point cross-connects.
Note |
For dynamic cross-connects, LDP must be up and running. |
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Step 1 |
configure Example:Enters the XR Config mode. |
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Step 2 |
l2vpn Example:Enters L2VPN configuration mode. |
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Step 3 |
xconnect group group-name Example:Enters the name of the cross-connect group. |
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Step 4 |
p2p xconnect-name Example:Enters a name for the point-to-point cross-connect. |
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Step 5 |
interworking ipv4 Example:Configure the interworking for IPv4. |
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Step 6 |
interface type interface-path-id Example:Specifies the interface type ID. The choices are:
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Step 7 |
neighbor ip-address pw-id pseudowire-id Example:Configures the pseudowire segment for the cross-connect. Optionally, you can disable the control word or set the transport-type to Ethernet or VLAN. |
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Step 8 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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The Inter-AS configuration procedure is identical to the L2VPN cross-connect configuration tasks (see “Configuring Static Point-to-Point Cross-Connects” section and “Configuring Dynamic Point-to-Point Cross-Connects” section) except that the remote PE IP address used by the cross-connect configuration is now reachable through iBGP peering.
Note |
You must be knowledgeable about IBGP, EBGP, and ASBR terminology and configurations to complete this configuration. |
Note |
The tunnel used for the preferred path configuration is an MPLS Traffic Engineering (MPLS-TE) tunnel. |
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Step 1 |
configure Example:Enters the configuration mode. |
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Step 2 |
l2vpn Example:Enters L2VPN configuration mode. |
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Step 3 |
pw-class {name } Example:Configures the pseudowire class name. |
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Step 4 |
encapsulation mpls Example:Configures the pseudowire encapsulation to MPLS. |
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Step 5 |
preferred-path {interface } {tunnel-ip value | tunnel-te value | tunnel-tp value } [fallback disable ] Example:Configures preferred path tunnel settings. If the fallback disable configuration is used and once the TE/TP tunnel is configured as the preferred path goes down, the corresponding pseudowire can also go down. |
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Step 6 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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Perform this task to enable load balancing with ECMP and FAT PW.
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Step 1 |
configure Example:Enters the XR Config mode. |
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Step 2 |
l2vpn Example:Enters the L2VPN configuration mode. |
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Step 3 |
pw-class {name} Example:Configures the pseudowire class name. |
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Step 4 |
encapsulation mpls Example:Configures the pseudowire encapsulation to MPLS. |
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Step 5 |
load-balancing flow-label both Example:Enables load-balancing on ECMPs. Also, enables the imposition and disposition of flow labels for the pseudowire. |
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Step 6 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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Perform this task to configure L2VPN Nonstop Routing.
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Step 1 |
configure Example:Enters XR Config mode. |
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Step 2 |
l2vpn Example:Enters the XR Config mode. |
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Step 3 |
nsr Example:Enables L2VPN nonstop routing. |
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Step 4 |
logging nsr Example:Enables logging of NSR events. |
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Step 5 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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Perform this task to enable Label Distribution Protocol (LDP) Nonstop Routing (NSR) for synchronizing label information between active and standby LDPs. From Release 6.1.1 onwards, with the introduction of stateful LDP feature, you must explicitly configure LDP NSR to synchronize label information between active and standby LDPs.
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Step 1 |
configure Example:Enters XR Config mode. |
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Step 2 |
mpls ldp Example:Enters MPLS LDP configuration mode. |
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Step 3 |
nsr Example:Enables LDP nonstop routing. |
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Step 4 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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This section provides information on
Perform this task to enable load balancing with ECMP and FAT PW for VPWS. Creating a PW-Class in L2VPN configuration leads to load-balancing.
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Step 1 |
configure Example:Enters the XR Config mode. |
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Step 2 |
l2vpn Example:Enters L2VPN configuration mode. |
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Step 3 |
pw-class { name } Example:Configures the pseudowire class template name to use for the pseudowire. |
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Step 4 |
encapsulation mpls Example:Configures the pseudowire encapsulation to MPLS. |
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Step 5 |
load-balancing flow-label { both | code | receive | transmit } [ static ] Example:Enables load-balancing on ECMPs. Also, enables the imposition and disposition of flow labels for the pseudowire.
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Step 6 |
exit Example:Exits the pseudowire encapsulation submode and returns the router to the parent configuration mode. |
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Step 7 |
exit Example:Exits the pseudowire submode and returns the router to the l2vpn configuration mode. |
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Step 8 |
xconnect group group-name Example:Specifies the name of the cross-connect group. |
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Step 9 |
p2p xconnect-name Example:Specifies the name of the point-to-point cross-connect. |
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Step 10 |
interface type interface-path-id Example:Specifies the interface type and instance. |
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Step 11 |
neighbor A.B.C.D pw-id pseudowire-id Example:Configures the pseudowire segment for the cross-connect. Use the A.B.C.D argument to specify the IP address of the cross-connect peer.
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Step 12 |
pw-class class-name Example:Associates the pseudowire class with this pseudowire. |
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Step 13 |
Use the commit or end command. commit - Saves the configuration changes and remains within the configuration session. end - Prompts user to take one of these actions:
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In the following example, two traffic classes are created and their match criteria are defined. For the first traffic class called class1, ACL 101 is used as the match criterion. For the second traffic class called class2, ACL 102 is used as the match criterion. Packets are checked against the contents of these ACLs to determine if they belong to the class.
This section includes the following configuration examples:
This example shows how to configure an L2VPN interface:
configure
interface TenGigE 0/0/0/0.1 l2transport
encapsulation dot1q 1
end
This section includes configuration examples for both static and dynamic p2p cross-connects.
This example shows how to configure a static point-to-point cross-connect:
configure
l2vpn
xconnect group vlan_grp_1
p2p vlan1
interworking ipv4
interface TenGigE 0/0/0/0.1
neighbor 2.2.2.2 pw-id 2000
mpls static label local 699 remote 890
commitThis example shows how to configure a dynamic point-to-point cross-connect:
configure
l2vpn
xconnect group vlan_grp_1
p2p vlan1
interface TenGigE 0/0/0/0.1
neighbor 2.2.1.1 pw-id 1
commitThis example shows how to set up an AC to AC cross-connect from AC1 to AC2:
This example shows how to configure preferred tunnel path:
configure
l2vpn
pw-class path1
encapsulation mpls
preferred-path interface tunnel-ip value fallback disableThis sample configuration shows how to enable load balancing with FAT PW for VPWS.
l2vpn
pw-class class1
encapsulation mpls
load-balancing flow-label transmit
!
!
pw-class class2
encapsulation mpls
load-balancing flow-label both
!
xconnect group group1
p2p p1
interface TenGigE 0/0/0/0.1
neighbor 10.0.0.1 pw-id 1
pw-class class1
!
!
! This example shows how to configure L2VPN Nonstop Routing.
config
l2vpn
nsr
logging nsr This sample configuration shows how to enable load balancing with FAT PW for VPWS.
l2vpn
pw-class class1
encapsulation mpls
load-balancing flow-label transmit
!
!
pw-class class2
encapsulation mpls
load-balancing flow-label both
!
xconnect group group1
p2p p1
interface TenGigE 0/0/0/0.1
neighbor 1.1.1.1 pw-id 1
pw-class class1
!
!
!
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