Configure Gigabit Ethernet for Layer 2 VPNs

This chapter introduces you to Layer 2 features and standards, and describes how you can configure L2VPN features.

The distributed Gigabit Ethernet (including 10-Gigabit and 100-Gigabit) architecture and features deliver network scalability and performance, while enabling service providers to offer high-density, high-bandwidth networking solutions designed to interconnect the router with other systems in POPs, including core and edge routers and Layer 2 and Layer 3 switches.

Introduction to Layer 2 Virtual Private Networks

A Layer 2 Virtual Private Network (VPN) emulates a physical sub-network in an IP or MPLS network, by creating private connections between two points. Building a L2VPN network requires coordination between the service provider and customer. The service provider establishes Layer 2 connectivity. The customer builds a network by using the data link resources obtained from the service provider. In a L2VPN service, the service provider does not require information about the customer's network topology and other information. This helps maintain customer privacy, while using the service provider resources to establish the network.

The service provider requires Provider Edge (PE) routers with the following capabilities:

  • Encapsulation of L2 protocol data units (PDU) into Layer 3 (L3) packets.
  • Interconnection of any-to-any L2 transports.
  • Support for MPLS tunneling mechanism.
  • Process databases that include all information related to circuits and their connections.

This section introduces Layer 2 Virtual Private Networks (VPNs) and the corresponding Gigabit Ethernet services.

Introduction to Layer 2 VPNs on Gigabit Ethernet Interfaces

A L2VPN network enables service providers (SPs) to provide L2 services to geographically disparate customer sites. Typically, a SP uses an access network to connect the customer to the core network. This access network may use a mixture of L2 technologies, such as Ethernet and Frame Relay. The connection between the customer site and the nearby SP edge router is known as an attachment circuit (AC). Traffic from the customer travels over this link to the edge of the SP core network. The traffic then tunnels through a pseudowire over the SP core network to another edge router. The edge router sends the traffic down another AC to the customer's remote site.

The L2VPN feature enables the connection between different types of L2 attachment circuits and pseudowires, allowing users to implement different types of end-to-end services.


Note

BOOTP traffic (dst UDP 68) over any type of pseudowire is unsupported.

Cisco IOS XR software supports a point-to-point end-to-end service, where two Ethernet circuits are connected together. An L2VPN Ethernet port can operate in one of two modes:

  • Port Mode—In this mode, all packets reaching the port are sent over the pseudowire, regardless of any VLAN tags that are present on the packets. In Port mode, the configuration is performed under the l2transport configuration mode.

  • VLAN Mode—Each VLAN on a CE (customer edge) or access network to PE (provider edge) link can be configured as a separate L2VPN connection (using either VC type 4 or VC type 5). To configure L2VPN on VLANs, see The Carrier Ethernet Model chapter in this manual. In VLAN mode, the configuration is performed under the individual sub-interface.

Switching can take place in the following ways:

  • AC-to-PW—Traffic reaching the PE is tunneled over a PW (pseudowire) (and conversely, traffic arriving over the PW is sent out over the AC). This is the most common scenario.

  • Local switching—Traffic arriving on one AC is immediately sent out of another AC without passing through a pseudowire.

  • PW stitching—Traffic arriving on a PW is not sent to an AC, but is sent back into the core over another PW.


Note

  • If your network requires that packets are transported transparently, you may need to modify the packet’s destination MAC (Media Access Control) address at the edge of the Service Provider (SP) network. This prevents the packet from being consumed by the devices in the SP network.

  • The encapsulation dot1ad vlan-id and encapsulation dot1ad vlan-id dot1q any commands cannot co-exist on the same physical interface or bundle interface. Similarly, the encapsulation dot1q vlan-id and encap dot1q vlan-id second-dot1q any commands cannot co-exist on the same physical interface or bundle interface. If there is a need to co-exist, it is recommended to use the exact keyword in the single tag encapsulation. For example, encap dot1ad vlan-id exact or encap dot1q vlan-id exact.

  • In an interface which already has QinQ configuration, you cannot configure the QinQ Range sub-interface where outer VLAN range of QinQ Range overlaps with outer VLAN of QinQ. Attempting this configuration results in the splitting of the existing QinQ and QinQ Range interfaces. However, the system can be recovered by deleting a recently configured QinQ Range interface.

  • In an interface which already has QinQ Range configuration, you cannot configure the QinQ Range sub-interface where outer VLAN range of QinQ Range overlaps with inner VLAN of QinQ Range. Attempting this configuration results in the splitting of the existing QinQ and QinQ Range interfaces. However, the system can be recovered by deleting a recently configured QinQ Range interface.

  • The inner VLAN ranges of sub-interfaces configured cannot have overlapping values. In such overlapping inner VLAN range cases, the system can be recovered by reloading the LC on Cisco IOS XR Release 6.5.x.

You can use the show interfaces command to display AC and pseudowire information.

Configure Gigabit Ethernet Interfaces for Layer 2 Transport

This section describes how you can configure Gigabit ethernet interfaces for Layer 2 transport.

Configuration Example 

RP/0/RP0/CPU0(config)#interface TenGigE 0/0/0/10

/* Configure the ethertype for the 802.1q encapsulation (optional) */
/* For VLANs, the default ethertype is 0x8100. In this example, we configure a value of 0x9100. 
/* The other assignable value is 0x9200 */
/* When ethertype is configured on a physical interface, it is applied to all sub-interfaces created on this interface */

RP/0/RP0/CPU0:router(config-if)#dot1q tunneling ethertype 0x9100 

/* Configure Layer 2 transport on the interface, and commit your configuration */
RP/0/RP0/CPU0:router(config-if)#l2transport 
RP/0/RP0/CPU0:router(config-if-l2)#commit 
Sat May  2 19:50:36.799 UTC
RP/0/RP0/CPU0:router(config-if-l2)#exit  
RP/0/RP0/CPU0:router(config-if)#no shutdown 
RP/0/RP0/CPU0:router(config-if)#exit
RP/0/RP0/CPU0:router(config)#

Running Configuration 


configure
 interface TenGigE 0/0/0/10
  dot1q tunneling ethertype 0x9100
  l2transport
 !

Verification

Verify that the Ten-Gigabit Ethernet interface is up and operational. 


router# show interfaces TenGigE 0/0/0/10

...
TenGigE0/0/0/10 is up, line protocol is up 
  Interface state transitions: 1
  Hardware is TenGigE, address is 0011.1aac.a05a (bia 0011.1aac.a05a)
  Layer 1 Transport Mode is LAN
  Layer 2 Transport Mode
  MTU 1514 bytes, BW 10000000 Kbit (Max: 10000000 Kbit)
     reliability 255/255, txload 0/255, rxload 0/255
  Encapsulation ARPA,
  Full-duplex, 10000Mb/s, link type is force-up
  output flow control is off, input flow control is off
  Carrier delay (up) is 10 msec
  loopback not set,
  ...

Associated Commands

Ethernet Data Plane Loopback

The Ethernet Data Plane Loopback function allows you to run loopback tests to test the connectivity and quality of connections through a Layer 2 cloud. You can run this test on:

  • Main interface or sub-interfaces

  • Bundle or its sub-interfaces

  • Multiple hops through the underlying network

You can use this feature to test the throughput of an Ethernet port remotely. You can verify the maximum rate of frame transmission with no frame loss.

This feature allows for bidirectional or unidirectional throughput measurement, and on-demand or out-of-service (intrusive) operation during service turn-up.

Two types of Ethernet loopback are supported:

  • External loopback - Traffic loopback occurs at the Ingress interface. Traffic does not flow into the router for loopback.

  • Internal loopback - Traffic loopback occurs at the Egress interface. Traffic loopback occurs after the traffic flows into the router to the other interface.


Note

The loopback {external | internal | line } command is not supported on Cisco NCS 560-4 (RSP4).

Ethernet data traffic can be looped back on per port basis. This feature supports a maximum of 100 concurrent Ethernet data plane loopback sessions per system. Filters based on frame header can be used for initiating the loopback session. This ensures that only a subset of traffic that is received on an interface is looped back. You can use Source MAC, Destination MAC, and VLAN Priority (COS bits) as filters.

Ethernet Data Plane Loopback Configuration Restrictions

These configuration restrictions are applicable for Ethernet Data Plane Loopback:

  • Ethernet data plane loopback is not supported on L3 interfaces or L3 sub-interfaces.

  • The following filters are not supported:

    • Outer VLAN or range of outer VLAN

    • Inner VLAN or range of inner VLAN

    • Ether type

  • Only the following combinations of filters are supported for external loopback:

    • Source MAC

    • Source MAC and Destination MAC

    • Source MAC, Destination MAC, and VLAN priority

    • Destination MAC

    • Destination MAC and VLAN priority

  • The rewrite modification on the loopback traffic is not supported.


    Note

    Ensure that no rewrite should be configured on subinterface.

  • Ethernet data plane loopback is not supported on packets with destination address as the broadcast MAC address.

  • Ethernet data plane loopback is not supported on BVI interface.

  • Ethernet data plane loopback is not supported on bridge-domian interfaces in Cisco IOS XR Release 6.3.2.

    Layer2 VPN bridge-domains internal loopback is not supported.

  • Only one Ethernet loopback session, either internal or external, can be active on the same interface at any given instance.

  • This feature supports a maximum throughput of 10Gbps for internal loopback over all the sessions. For external loopback, there is no throughput limit.

  • Dropping of packets that are received in the non-loopback direction is not supported.

  • Ethernet data plane loopback is not supported on packets having destination as multicast and broadcast MAC address.

  • External and internal Ethernet data plane loopback is not supported over bridge domain.

  • The Cisco NCS 560 Series Routers do not support Ethernet loopback (external and internal) on Layer2 VPN bridge-domain.

Configure Ethernet Data Plane Loopback

This section describes how you can configure Ethernet Data Plane Loopback on physical interface and sub-interface. Configuring Ethernet Data Plane Loopback involves these steps:

  • Configuring Ethernet Data Plane External Loopback

  • Starting an Ethernet Data Plane Loopback Session

Configuration Example 

/* Configuring Ethernet Data Plane External Loopback */

/* On physical interface */

RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface tenGigE 0/0/0/0 l2transport 
RP/0/RSP0/CPU0:router((config-if-l2)# ethernet loopback permit external

/* Starting an Ethernet Data Plane Loopback Session  */

RP/0/RSP0/CPU0:router# ethernet loopback start local interface tenGigE 0/0/0/0 external source mac-address 0000.0000.0001 destination mac-address 0000.0000.0002 cos 5 timeout none


/* On physical sub-interface */

RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface tenGigE 0/2/0/0/0.1 l2transport 
RP/0/RSP0/CPU0:router(config-subif)# encapsulation dot1q 100
RP/0/RSP0/CPU0:router((config-if-l2)# ethernet loopback permit external

/* Starting an Ethernet Data Plane Loopback Session  */

RP/0/RSP0/CPU0:router# ethernet loopback start local interface tenGigE 0/2/0/0/0.1 external source mac-address 0000.0000.0001 destination mac-address 0000.0000.0002 cos 5 timeout none

/* Configuring Ethernet Data Plane Internal Loopback */

/* On physical interface

RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface tenGigE 0/0/0/1 l2transport 
RP/0/RSP0/CPU0:router((config-if-l2)# ethernet loopback permit internal

/* Starting an Ethernet Data Plane Loopback Session  */

RP/0/RSP0/CPU0:router# ethernet loopback start local interface tenGigE 0/0/0/1 internal source mac-address 0000.0000.0002 destination mac-address 0000.0000.0003 cos 5 timeout none


/* On physical sub-interface */  

RP/0/RSP0/CPU0:router# configure 
RP/0/RSP0/CPU0:router(config)# interface tenGigE 0/2/0/0/0.1 l2transport 
RP/0/RSP0/CPU0:router(config-subif)# encapsulation dot1q 100
RP/0/RSP0/CPU0:router(config-if-l2)# ethernet loopback permit internal  

/* Starting an Ethernet Data Plane Loopback Session  */

RP/0/RSP0/CPU0:router# ethernet loopback start local interface tenGigE 0/2/0/0/0.1 internal source mac-address 0000.0000.0002 destination mac-address 0000.0000.0003 cos 5 timeout none



/* Stopping an Ethernet Data Plane Loopback Session */

RP/0/RSP0/CPU0:router# ethernet loopback stop local interface tenGigE 0/0/0/0 id 1
RP/0/RSP0/CPU0:router# ethernet loopback stop local interface tenGigE 0/0/0/1 id 2
RP/0/RSP0/CPU0:router# ethernet loopback stop local interface tenGigE 0/2/0/0/0.1 id 1

Similarly, you can configure the Ethernet Data Plane Loopback session for bundle interface and bundle sub-interface.

Ethernet loopback works even after SSO.

Running Configuration

This section shows Ethernet Data Plane Loopback running configuration. 

/* External Loopback */

/* On physical interface */

configure
 interface interface tenGigE 0/0/0/0 l2transport
  ethernet loopback permit external
 !

/* On physical sub-interface */

configure
 interface interface tenGigE 0/2/0/0/0.1 l2transport
  encapsulation dot1q 100
  ethernet loopback permit external
 !



/* Internal Loopback */

/* On physical interface */

configure
 interface interface tenGigE 0/0/0/1 l2transport
  ethernet loopback permit internal
 !

/* On physical sub-interface */

configure
 interface interface tenGigE 0/2/0/0/0.1 l2transport
  encapsulation dot1q 100
  ethernet loopback permit internal
 !

Verification

The following example displays the loopback capabilities per interface. The output shows internal loopback has been permitted on Ten Gigabit Ethernet 0/0/0/1 interface and external loopback has been permitted on Ten Gigabit Ethernet 0/0/0/0 interface. 



RP/0/RSP0/CPU0:router# show ethernet loopback permitted 

--------------------------------------------------------------------------------
Interface                               Dot1q(s)                       Direction
--------------------------------------------------------------------------------
tenGigE 0/0/0/1.1                        100                             Internal
tenGigE 0/0/0/0.1                        100                             External
---------------------------------------------------------------------------------


/* This example shows all active sessions on the router */

RP/0/RSP0/CPU0:router# show ethernet loopback active   
Thu Jul 20 11:00:57.864 UTC
Local: TenGigE0/0/0/0.1, ID 1
============================================
Direction:                          External
Time out:                               None
Time left:                                 -
Status:                               Active
Filters:
  Dot1Q:                                 Any
  Second-dot1Q:                          Any
  Source MAC Address:                    Any
  Destination MAC Address:               Any
  Class of Service:                      Any
Local: TenGigE0/0/0/0.1, ID 2
============================================
Direction:                          External
Time out:                               None
Time left:                                 -
Status:                               Active
Filters:
  Dot1Q:                                 Any
  Second-dot1Q:                          Any
  Source MAC Address:         0000.0000.0001
  Destination MAC Address:    0000.0000.0002
  Class of Service:                        5
Related Topics
Associated Commands

  • ethernet loopback

  • show ethernet loopback