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Example: Interconnecting a Layer 2 Circuit with a Layer 2 Circuit

This example provides a step-by-step procedure and commands for configuring and verifying a Layer 2 circuit to a Layer 2 circuit interconnection. It contains the following sections:

Requirements

This example uses the following hardware and software components:

  • Junos OS Release 9.3 or later
  • 2 MX Series routers
  • 2 M Series routers
  • 1 T Series router
  • 1 EX Series router
  • 1 J Series router

Overview and Topology

The physical topology of a Layer 2 circuit to Layer 2 circuit interconnection is shown in Figure 1

Figure 1: Physical Topology of a Layer 2 Circuit Terminating into a Layer 2 Circuit

Physical Topology of a Layer 2 Circuit Terminating into a Layer 2 Circuit

The logical topology of a Layer 2 circuit to Layer 2 circuit interconnection is shown in Figure 2

Figure 2: Logical Topology of a Layer 2 Circuit Terminating into a Layer 2 Circuit

Logical Topology of a Layer 2 Circuit Terminating into a Layer 2 Circuit

Configuration

Note: In any configuration session, it is good practice to verify periodically that the configuration can be committed using the commit check command.

In this example, the router being configured is identified using the following command prompts:

  • CE2 identifies the customer edge 2 (CE2) router
  • PE1 identifies the provider edge 1 (PE1) router
  • CE3 identifies the customer edge 3 (CE3) router
  • PE3 identifies the provider edge 3 (PE3) router
  • CE5 identifies the customer edge 5 (CE5) router
  • PE5 identifies the provider edge 5 (PE5) router

This example contains the following procedures:

Configuring PE Router Customer-facing and Loopback Interfaces

Step-by-Step Procedure

To begin building the interconnection, configure the interfaces on the PE routers. If your network contains provider (P) routers, configure the interfaces on the P routers also. This example shows the configuration for Router PE1 and Router PE5.

  1. On Router PE1, configure the ge-1/0/0 interface encapsulation. To configure the interface encapsulation, include the encapsulation statement and specify the ethernet-ccc option (vlan-ccc encapsulation is also supported). Configure the ge-1/0/0.0 logical interface family for circuit cross-connect functionality. To configure the logical interface family, include the family statement and specify the ccc option.
    [edit interfaces]
    ge-1/0/0 {encapsulation ethernet-ccc;unit 0 {family ccc;}}
    lo0 {unit 0 {family inet {address 1.1.1.1/32;}}}
  2. On Router PE5, configure the ge-2/0/0 interface encapsulation. To configure the interface encapsulation, include the encapsulation statement and specify the ethernet-ccc option. Configure the ge-2/0/0.0 logical interface family for circuit cross-connect functionality. To configure the logical interface family, include the family statement and specify the ccc option
    [edit interfaces]
    ge-2/0/0 {encapsulation ethernet-ccc;unit 0 {family ccc;}}
    lo0 {unit 0 {family inet {address 5.5.5.5/32;}}}
  3. On Router PE3, configure the logical loopback interface. The loopback interface is used to establish the targeted LDP sessions to Routers PE1 and PE5.
    [edit interfaces]
    lo0 {unit 0 {family inet {address 3.3.3.3/32;}}}

Configuring Core-facing Interfaces

Step-by-Step Procedure

This procedure describes how to configure the core-facing interfaces on the PE routers. This example does not include all the core-facing interfaces shown in the physical topology illustration. Enable the mpls and inet address families on the core-facing interfaces.

  1. On Router PE1, configure the xe-0/3/0 interface. Include the family statement and specify the inet address family. Include the address statement and specify 10.10.1.1/30 as the interface address. Include the family statement and specify the mpls address family.
    [edit interfaces]
    xe-0/3/0 {unit 0 {family inet {address 10.10.1.1/30;}family mpls;}}
  2. On Router PE3, configure the core-facing interfaces. Include the family statement and specify the inet address family. Include the address statement and specify the IPv4 addresses shown in the example as the interface addresses. Include the family statement and specify the mpls address family. In the example, the xe-0/0/0 interface is connected to the route reflector, the xe-0/1/0 interface is connected to Router PE5, the xe-0/2/0 interface is connected to Router PE2, and the xe-0/3/0 interface is connected to Router PE1.
    [edit interfaces]
    xe-0/0/0 {unit 0 {family inet {address 10.10.20.2/30;}family mpls;}}
    xe-0/1/0 {unit 0 {family inet {address 10.10.6.1/30;}family mpls;}}
    xe-0/2/0 {unit 0 {family inet {address 10.10.5.2/30;}family mpls;}}
    xe-0/3/0 {unit 0 {family inet {address 10.10.1.2/30;}family mpls;}}
  3. On Router PE5, configure the xe-0/1/0 interface. Include the family statement and specify the inet address family. Include the address statement and specify 10.10.6.2/30 as the interface address. Include the family statement and specify the mpls address family.
    [edit interfaces]
    xe-0/1/0 {unit 0 {family inet {address 10.10.6.2/30;}family mpls;}}

Configuring Protocols

Step-by-Step Procedure

This procedure describes how to configure the protocols used in this example. If your network contains P routers, configure the protocols on the P routers also.

Configure all of the PE routers and P routers with OSPF as the IGP protocol. Enable MPLS and LDP protocols on all of the interfaces except fxp.0.

  1. On Router PE1, enable OSPF as the IGP. Enable the MPLS and LDP protocols on all interfaces except fxp.0. LDP is used as the signaling protocol on Router PE1 for the Layer 2 circuit. The following configuration snippet shows the protocol configuration for Router PE1:
    [edit]
    protocols {mpls {interface all;interface fxp0.0 {disable;}}ospf {traffic-engineering;area 0.0.0.0 {interface all;interface fxp0.0 {disable;}}}ldp {interface all;interface fxp0.0 {disable;}}}
  2. Configure the PE and P routers with OSPF as the IGP. Enable the MPLS and LDP protocols on all interfaces except fxp.0. The following configuration snippet shows the protocol configuration for Router PE3:
    [edit]
    protocols {mpls {interface all;interface fxp0.0 {disable;}}ospf {traffic-engineering;area 0.0.0.0 {interface all;interface fxp0.0 {disable;}}}ldp {interface all;interface fxp0.0 {disable;}}}

Configuring the Layer 2 Circuits

Step-by-Step Procedure

This procedure describes how to configure the Layer 2 circuits.

Note: In this example the ignore-mtu-mismatch statement is required for the circuit to come up.

  1. On Router PE1, configure the Layer 2 circuit. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE3 as the neighbor. Include the interface statement and specify ge-1/0/0.0 as the logical interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 100 as the identifier. Include the ignore-mtu-mismatch statement to allow a Layer 2 circuit to be established even though the maximum transmission unit (MTU) configured on the local PE router does not match the MTU configured on the remote PE router.
    [edit]
    protocols {l2circuit {neighbor 3.3.3.3 {interface ge-1/0/0.0 {virtual-circuit-id 100;ignore-mtu-mismatch;}}}}
  2. On Router PE5, configure the Layer 2 circuit. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE3 as the neighbor. Include the interface statement and specify ge-2/0/0.0 as the logical interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 200 as the identifier. Include the ignore-mtu-mismatch statement to allow a Layer 2 circuit to be established even though the MTU configured on the local PE router does not match the MTU configured on the remote PE router.
    [edit]
    protocols {l2circuit {neighbor 3.3.3.3 {interface ge-2/0/0.0 {virtual-circuit-id 200;ignore-mtu-mismatch;}}}}
  3. On Router PE3, configure the Layer 2 circuit to Router PE1. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE1 as the neighbor. Include the interface statement and specify iw0.0 as the logical interworking interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 100 as the identifier. Include the ignore-mtu-mismatch statement to allow a Layer 2 circuit to be established even though the MTU configured on the local PE router does not match the MTU configured on the remote PE router.

    On Router PE3, configure the Layer 2 circuit to Router PE5. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE5 as the neighbor. Include the interface statement and specify iw0.1 as the logical interworking interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 200 as the identifier. Include the ignore-mtu-mismatch statement.

    [edit protocols]
    l2circuit {neighbor 1.1.1.1 {interface iw0.0 {virtual-circuit-id 100;ignore-mtu-mismatch;}}neighbor 5.5.5.5 {interface iw0.1 {virtual-circuit-id 200;ignore-mtu-mismatch;}}}

Interconnecting the Layer 2 Circuits

Step-by-Step Procedure

Router PE3 is the router that is stitching the Layer 2 circuits together using the interworking interface. The configuration of the peer unit interfaces is what makes the interconnection.

  1. On Router PE3, configure the iw0.0 interface. Include the encapsulation statement and specify the ethernet-ccc option. Include the peer-unit statement and specify the logical interface unit 1 as the peer tunnel interface.

    On Router PE3, configure the iw0.1 interface. Include the encapsulation statement and specify the ethernet-ccc option. Include the peer-unit statement and specify the logical interface unit 0 as the peer tunnel interface.

    [edit interfaces]
    iw0 {unit 0 {encapsulation ethernet-ccc;peer-unit 1;}unit 1 {encapsulation ethernet-ccc;peer-unit 0;}}
  2. On Router PE3, configure the Layer 2 interworking l2iw protocol. To configure the Layer 2 interworking protocol, include the l2iw statement at the [edit protocols] hierarchy level.
    [edit]
    protocols {l2iw;}
  3. On each router, commit the configuration.
    user@host> commit checkconfiguration check succeedsuser@host> commit

Verifying the Layer 2 Circuit to Layer 2 Circuit Interconnection

Step-by-Step Procedure

Verify that the Layer 2 circuit connection on Router PE1 is up, the LDP neighbors are correct, and the MPLS label operations are correct.

  1. On Router PE1, use the show l2circuit connections command to verify that the Layer 2 circuit from Router PE1 to Router PE3 is Up.
    user@PE1> show l2circuit connections
    Layer-2 Circuit Connections:
Legend for connection status (St)   
EI -- encapsulation invalid      NP -- interface h/w not present   
MM -- mtu mismatch               Dn -- down                       
EM -- encapsulation mismatch     VC-Dn -- Virtual circuit Down    
CM -- control-word mismatch      Up -- operational                
VM -- vlan id mismatch           CF -- Call admission control failure
OL -- no outgoing label          IB -- TDM incompatible bitrate 
NC -- intf encaps not CCC/TCC    TM -- TDM misconfiguration 
BK -- Backup Connection          ST -- Standby Connection
CB -- rcvd cell-bundle size bad  XX -- unknown
SP -- Static Pseudowire

Legend for interface status  
Up -- operational            
Dn -- down                   
Neighbor: 3.3.3.3 
    Interface                 Type  St     Time last up   # Up trans
    ge-1/0/0.0(vc 100)        rmt   Up     Jan  5 22:00:49 2010    1
      Remote PE: 3.3.3.3, Negotiated control-word: Yes (Null)
      Incoming label: 301328, Outgoing label: 314736
      Local interface: ge-1/0/0.0, Status: Up, Encapsulation: ETHERNET
  2. On Router PE1, use the show ldp neighbor command to verify that the IPv4 address of Router PE3 is shown as the LDP neighbor.
    user@PE1> show ldp neighbor
    Address            Interface          Label space ID         Hold time
3.3.3.3            lo0.0              3.3.3.3:0                41
  3. On Router PE 1, use the show route table mpls.0 command to verify the Layer 2 circuit is using the LDP label to Router PE3 in both directions (Push and Pop). In the example below, the Layer 2 circuit is associated with LDP label 301328.
    user@PE1> show route table mpls.0
    mpls.0: 13 destinations, 13 routes (13 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0                  *[MPLS/0] 1w1d 08:25:39, metric 1
                      Receive
1                  *[MPLS/0] 1w1d 08:25:39, metric 1
                      Receive
2                  *[MPLS/0] 1w1d 08:25:39, metric 1
                      Receive
300432             *[LDP/9] 3d 01:13:57, metric 1
                    > to 10.10.2.2 via xe-0/1/0.0, Pop      
300432(S=0)        *[LDP/9] 3d 01:13:57, metric 1
                    > to 10.10.2.2 via xe-0/1/0.0, Pop      
300768             *[LDP/9] 3d 01:13:57, metric 1
                    > to 10.10.3.2 via xe-0/2/0.0, Pop      
300768(S=0)        *[LDP/9] 3d 01:13:57, metric 1
                    > to 10.10.3.2 via xe-0/2/0.0, Pop      
300912             *[LDP/9] 3d 01:13:57, metric 1
                    > to 10.10.3.2 via xe-0/2/0.0, Swap 299856
301264             *[LDP/9] 3d 01:13:53, metric 1
                    > to 10.10.1.2 via xe-0/3/0.0, Swap 308224
301312             *[LDP/9] 3d 01:13:56, metric 1
                    > to 10.10.1.2 via xe-0/3/0.0, Pop      
301312(S=0)        *[LDP/9] 3d 01:13:56, metric 1
                    > to 10.10.1.2 via xe-0/3/0.0, Pop      
301328             *[L2CKT/7] 02:33:26                     > via ge-1/0/0.0, Pop       Offset: 4 ge-1/0/0.0         *[L2CKT/7] 02:33:26, metric2 1                     > to 10.10.1.2 via xe-0/3/0.0, Push 314736 Offset: -4
  4. On Router PE3, use the show l2circuit connections command to verify that the Layer 2 circuit from Router PE3 to Router PE5 is Up, that the Layer 2 circuit from Router PE3 to Router PE1 is Up, that the connections to Router PE1 and Router PE5 use the iw0 interface, and that the status for both local iw0 interfaces is Up.
    user@PE3> show l2circuit connections
    Layer-2 Circuit Connections:
Legend for connection status (St)   
EI -- encapsulation invalid      NP -- interface h/w not present   
MM -- mtu mismatch               Dn -- down                       
EM -- encapsulation mismatch     VC-Dn -- Virtual circuit Down    
CM -- control-word mismatch      Up -- operational                
VM -- vlan id mismatch           CF -- Call admission control failure
OL -- no outgoing label          IB -- TDM incompatible bitrate 
NC -- intf encaps not CCC/TCC    TM -- TDM misconfiguration 
BK -- Backup Connection          ST -- Standby Connection
CB -- rcvd cell-bundle size bad  XX -- unknown
SP -- Static Pseudowire

Legend for interface status  
Up -- operational            
Dn -- down                   
Neighbor: 1.1.1.1 
    Interface                 Type  St     Time last up          # Up trans
    iw0.0(vc 100)             rmt   Up     Jan  5 13:50:14 2010           1
      Remote PE: 1.1.1.1, Negotiated control-word: Yes (Null)
      Incoming label: 314736, Outgoing label: 301328
      Local interface: iw0.0, Status: Up, Encapsulation: ETHERNET
Neighbor: 5.5.5.5 
    Interface                 Type  St     Time last up          # Up trans
    iw0.1(vc 200)             rmt   Up     Jan  5 13:49:58 2010           1
      Remote PE: 5.5.5.5, Negotiated control-word: Yes (Null)
      Incoming label: 314752, Outgoing label: 300208
      Local interface: iw0.1, Status: Up, Encapsulation: ETHERNET
  5. On Router PE3, use the show ldp neighbor command to verify that the correct IPv4 addresses are shown as the LDP neighbor.
    user@PE3> show ldp neighbor
    Address            Interface          Label space ID         Hold time
1.1.1.1            lo0.0              1.1.1.1:0                44
2.2.2.2            lo0.0              2.2.2.2:0                42
4.4.4.4            lo0.0              4.4.4.4:0                31
5.5.5.5            lo0.0              5.5.5.5:0                44
  6. On Router PE3, use the show route table mpls.0 command to verify that the mpls.0 routing table is populated with the Layer 2 interworking routes. Notice that in this example, the router is swapping label 314736 received from Router PE1 on the iw0.0 to label 301328.
    user@PE3> show route table mpls.0
    mpls.0: 16 destinations, 18 routes (16 active, 2 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0                  *[MPLS/0] 1w1d 08:28:24, metric 1
                      Receive
1                  *[MPLS/0] 1w1d 08:28:24, metric 1
                      Receive
2                  *[MPLS/0] 1w1d 08:28:24, metric 1
                      Receive
308160             *[LDP/9] 3d 01:16:55, metric 1
                    > to 10.10.1.1 via xe-0/3/0.0, Pop      
308160(S=0)        *[LDP/9] 3d 01:16:55, metric 1
                    > to 10.10.1.1 via xe-0/3/0.0, Pop      
308176             *[LDP/9] 3d 01:16:54, metric 1
                    > to 10.10.6.2 via xe-0/1/0.0, Pop      
308176(S=0)        *[LDP/9] 3d 01:16:54, metric 1
                    > to 10.10.6.2 via xe-0/1/0.0, Pop      
308192             *[LDP/9] 00:21:40, metric 1
                    > to 10.10.20.1 via xe-0/0/0.0, Swap 601649
                      to 10.10.6.2 via xe-0/1/0.0, Swap 299856
308208             *[LDP/9] 3d 01:16:54, metric 1
                    > to 10.10.5.1 via xe-0/2/0.0, Pop      
308208(S=0)        *[LDP/9] 3d 01:16:54, metric 1
                    > to 10.10.5.1 via xe-0/2/0.0, Pop      
308224             *[LDP/9] 3d 01:16:52, metric 1
                    > to 10.10.20.1 via xe-0/0/0.0, Pop      
308224(S=0)        *[LDP/9] 3d 01:16:52, metric 1
                    > to 10.10.20.1 via xe-0/0/0.0, Pop      
314736             *[L2IW/6] 02:35:31, metric2 1
                    > to 10.10.6.2 via xe-0/1/0.0, Swap 300208
                    [L2CKT/7] 02:35:31
                    > via iw0.0, Pop       Offset: 4
314752             *[L2IW/6] 02:35:31, metric2 1
                    > to 10.10.1.1 via xe-0/3/0.0, Swap 301328
                    [L2CKT/7] 02:35:47
                    > via iw0.1, Pop       Offset: 4
iw0.0              *[L2CKT/7] 02:35:31, metric2 1
                    > to 10.10.1.1 via xe-0/3/0.0, Push 301328 Offset: -4
iw0.1              *[L2CKT/7] 02:35:47, metric2 1
                    > to 10.10.6.2 via xe-0/1/0.0, Push 300208 Offset: -4
  7. Verify that Router CE1 can send traffic to and receive traffic from Router CE5 across the interconnection, using the ping command.
    user@CE1>ping 40.40.40.11
    PING 40.40.40.11 (40.40.40.11): 56 data bytes
64 bytes from 40.40.40.11: icmp_seq=1 ttl=64 time=22.425 ms
64 bytes from 40.40.40.11: icmp_seq=2 ttl=64 time=1.299 ms
64 bytes from 40.40.40.11: icmp_seq=3 ttl=64 time=1.032 ms
64 bytes from 40.40.40.11: icmp_seq=4 ttl=64 time=1.029 ms
  8. Verify that Router CE5 can send traffic to and receive traffic from Router CE1 across the interconnection, using the ping command.
    user@CE5>ping 40.40.40.1
    PING 40.40.40.1 (40.40.40.1): 56 data bytes
64 bytes from 40.40.40.1: icmp_seq=0 ttl=64 time=1.077 ms
64 bytes from 40.40.40.1: icmp_seq=1 ttl=64 time=0.957 ms
64 bytes from 40.40.40.1: icmp_seq=2 ttl=64 time=1.057 ms 1.017 ms

Results

The configuration and verification of this example has been completed. The following section is for your reference.

The relevant sample configuration for Router PE1 follows.

Router PE1

[edit]
interfaces {xe-0/1/0 {unit 0 {family inet {address 10.10.2.1/30;}family mpls;}}xe-0/2/0 {unit 0 {family inet {address 10.10.3..1/30;}family mpls;}}xe-0/3/0 {unit 0 {family inet {address 10.10.1.1/30;}family mpls;}}ge-1/0/0 {encapsulation ethernet-ccc;unit 0 {family ccc;}}lo0 {unit 0 {family inet {address 1.1.1.1/32;}}}}
forwarding-options {hash-key {family inet {layer-3;layer-4;}family mpls {label-1;label-2;}}}
routing-options {static {route 172.0.0.0/8 next-hop 172.19.59.1;}autonomous-system 65000;}
protocols {mpls {interface all;interface fxp0.0 {disable;}}ospf {traffic-engineering;area 0.0.0.0 {interface all;interface fxp0.0 {disable;}}}ldp {interface all;interface fxp0.0 {disable;}}l2circuit {neighbor 3.3.3.3 {interface ge-1/0/0.0 {virtual-circuit-id 100;ignore-mtu-mismatch;}}}}

The relevant sample configuration for Router PE3 follows.

Router PE3

[edit]
interfaces {xe-0/0/0 {unit 0 {family inet {address 10.10.20.2/30;}family mpls;}}xe-0/1/0 {unit 0 {family inet {address 10.10.6.1/30;}family mpls;}}xe-0/2/0 {unit 0 {family inet {address 10.10.5.2/30;}family mpls;}}xe-0/3/0 {unit 0 {family inet {address 10.10.1.2/30;}family mpls;}}ge-1/0/1 {encapsulation ethernet-ccc;unit 0 {family ccc;}}iw0 {unit 0 {encapsulation ethernet-ccc;peer-unit 1;}unit 1 {encapsulation ethernet-ccc;peer-unit 0;}}lo0 {unit 0 {family inet {address 3.3.3.3/32;}}}}
routing-options {static {route 172.0.0.0/8 next-hop 172.19.59.1;}autonomous-system 65000;}
protocols {l2iw;mpls {interface all;interface fxp0.0 {disable;}}ospf {area 0.0.0.0 {interface all;interface fxp0.0 {disable;}}}ldp {interface all;interface fxp0.0 {disable;}}l2circuit {neighbor 1.1.1.1 {interface iw0.0 {virtual-circuit-id 100;ignore-mtu-mismatch;}}neighbor 5.5.5.5 {interface iw0.1 {virtual-circuit-id 200;ignore-mtu-mismatch;}}}}
 

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Published: 2013-02-28

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