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Example: Ethernet-Based Layer 2 Circuit Configuration

Figure 1: Ethernet-Based Layer 2 Circuit Topology Diagram

Image g017138.gif

In Figure 1, a Layer 2 circuit is established between routers PE1 and PE2 to deliver Layer 2 traffic between customer routers CE1 and CE2. A Layer 2 circuit VC connection is configured on the PE routers only. No special configuration is required on the CE routers, and the provider core P0 router only requires MPLS and LDP on the appropriate interfaces to enable labels to be shared between the PE routers.

On Router CE1, configure the Fast Ethernet interface to handle VLAN traffic. Be sure to use the same VLAN ID both here and on the Fast Ethernet interface of Router CE2.

Router CE1

[edit]interfaces {fe-1/1/2 {description "to PE1 fe-1/1/0";vlan-tagging;unit 600 { vlan-id 600; # Be sure this VLAN ID matches the VLAN ID of your CE neighbor.family inet {address 10.1.1.1/24;}}}}

On Router PE1, configure the Ethernet-based CE-facing interface with the CCC encapsulation type of your choice. If you use VLAN CCC, include the vlan-tagging statement at the [edit interfaces ethernet-interface-fpc/pic /port] hierarchy level. Also, include the encapsulation vlan-ccc statement at both the [edit interfaces ethernet-interface-fpc/pic/port] and [edit interfaces ethernet-interface-fpc /pic/port unit unit-number] hierarchy levels.

Establish your Layer 2 circuit with configuration of the l2circuit statement at the [edit protocols] hierarchy level. Remember to include in your Layer 2 circuit configuration the IP address of your remote PE neighbor (usually the loopback address of the neighbor), the interface connected to the CE router, and a virtual circuit identifier for this VC. Then, configure MPLS, LDP, and an IGP (such as OSPF) to enable signaling for your Layer 2 circuit.

Router PE1

[edit]interfaces {so-0/1/0 {description "to P0 so-0/0/0";unit 0 {family inet {address 192.168.245.22/30;}family mpls; # Include the MPLS family on core-facing interfaces.}}fe-1/1/0 {description "to CE1 fe-1/1/2";vlan-tagging; encapsulation vlan-ccc; # Configure CCC encapsulation on CE-facing interfaces.unit 600 { encapsulation vlan-ccc; # Enable this encapsulation on the logical interface.vlan-id 600;}}lo0 {unit 0 {family inet {address 10.245.14.173/32;}}}}protocols {ospf {traffic-engineering;area 0.0.0.0 {interface so-0/1/0.0;interface lo0.0;}}ldp { # LDP is required as the signaling protocol for Layer 2 circuits.interface so-0/1/0.0;interface lo0.0;# You must include the loopback address in LDP.}l2circuit {neighbor 10.245.14.179 { # This points to the loopback of the PE neighbor.interface fe-1/1/0.600 { # Here you include the local CE-facing interface.virtual-circuit-id 5; # Be sure this ID matches the ID of your PE neighbor.}}}}

On Router P0, configure LDP, MPLS, and OSPF on the interfaces connected to the PE routers. The core router provides the MPLS backbone needed to tunnel Layer 2 traffic from the ingress PR router to the egress PE router.

Router P0

[edit]interfaces {so-0/0/0 {description "to PE1 so-0/1/0";unit 0 {family inet {address 192.168.245.21/30;}family mpls; # Include the MPLS family on core interfaces.}}t3-0/2/1 {description "to PE2 t3-0/1/0";unit 0 {family inet {address 192.168.245.17/30;}family mpls; # Include the MPLS family on core interfaces.}}lo0 {unit 0 {family inet {address 10.245.14.171/32;}}}}protocols {ospf {traffic-engineering;area 0.0.0.0 {interface so-0/0/0.0;interface t3-0/2/1.0;}}ldp { # LDP is required as the signaling protocol for Layer 2 circuits.interface so-0/0/0.0;interface t3-0/2/1.0;}}

On Router PE2, complete the Layer 2 circuit by configuring statements to match those previously set on Router PE1. Configure the Ethernet-based CE-facing interface with CCC encapsulation. Again, you must include the vlan-tagging statement at the [edit interfaces ethernet-interface-fpc/pic/port] hierarchy level when you use VLAN CCC. Also, include the encapsulation vlan-ccc statement at both the [edit interfaces ethernet-interface-fpc/pic/port] and [edit interfaces ethernet-interface-fpc/pic/port unit unit-number] hierarchy levels.

Establish your Layer 2 circuit with configuration of the l2circuit statement at the [edit protocols] hierarchy level. Remember to include in your Layer 2 circuit configuration the IP address of your remote PE neighbor (Router PE1), the virtual circuit identifier previously configured on Router PE1, and the interface connected to the CE router. Finally, configure MPLS, LDP, and OSPF to enable signaling for your Layer 2 circuit.

Router PE2

[edit]interfaces {t3-0/1/0 {description "P0 t3-0/2/1";unit 0 {family inet {address 192.168.245.18/30;}family mpls; # Include the MPLS family on core-facing interfaces.}}fe-0/2/0 {description "to CE2 fe-0/2/0";vlan-tagging; encapsulation vlan-ccc; # Configure CCC encapsulation on CE-facing interfaces.unit 600 { encapsulation vlan-ccc; # Enable this encapsulation on the logical interface.vlan-id 600;}}lo0 {unit 0 {family inet {address 10.245.14.179/32;}}}}protocols {ospf {traffic-engineering;area 0.0.0.0 {interface t3-0/1/0.0;interface lo0.0;}}ldp { # LDP is required as the signaling protocol for Layer 2 circuits.interface t3-0/1/0.0;interface lo0.0; # You must include the loopback address in LDP.}l2circuit {neighbor 10.245.14.173 { # This points to the loopback of the PE neighbor.interface fe-0/2/0.600 { # Here you include the local CE-facing interface.virtual-circuit-id 5; # Be sure this ID matches the ID of your PE neighbor.}}}}

On Router CE2, configure the Fast Ethernet interface to handle VLAN traffic. Be sure to use the same VLAN ID on this interface as the one seen on the Fast Ethernet interface of Router CE1.

Router CE2

[edit]interfaces {fe-0/2/0 {description "to PE2 fe-0/2/0";vlan-tagging;unit 600 {vlan-id 600; # Be sure this VLAN ID matches the VLAN ID of your CE neighbor.family inet {address 10.1.1.2/24;}}}}

Verifying Your Work

To verify proper operation of Layer 2 circuits, use the following commands:

  • ping mpls l2circuit interfaceinterface-name
  • ping mpls l2circuit virtual-circuit virtual-circuit-id neighbor ip-address
  • show l2circuit connections
  • Options: [brief] | [down] | [extensive] | [history] | [instance] | [local-site] | [remote-site] |[status] | [summary] | [up] | [up-down]
  • show ldp database

In addition to displaying bindings for IP prefixes, the show ldp database command also displays the bindings for the Layer 2 FECs.

The following sections show the output of these commands used with the configuration example:

Router PE1 Status


user@PE1> show l2circuit connections
Layer-2 Circuit Connections:

Legend for connection status (St)   Legend for interface status
EI -- encapsulation invalid         UP -- operational
MM -- mtu mismatch                  Dn -- down
EM -- encapsulation mismatch        NP -- no present
OL -- no outgoing label             DS -- disabled
Dn -- down                          WE -- wrong encapsulation
VC-Dn -- Virtual circuit Down       UN -- uninitialized
UP -- operational
XX -- unknown

Neighbor: 10.245.14.179
    Interface                 Type  St     Time last up          # Up trans
    fe-1/1/0.600 (vc 5)       rmt   Up     Nov 30 00:54:55 2001           1
      Local interface: fe-1/1/0.600, Status: Up,  Encapsulation: VLAN
      Remote PE: 10.245.14.179,  Negotiated control-word: Yes (Null)
      Incoming label: 100007, Outgoing label: 100000

user@PE1>  show ldp database

Input label database, 10.245.14.173:0-10.245.14.171:0
  Label     Prefix
 100019     10.245.14.173/32
 100020     10.245.14.179/32
      3     10.245.14.171/32

Output label database, 10.245.14.173:0-10.245.14.171:0
  Label     Prefix
 100009     10.245.14.179/32
      3     10.245.14.173/32
 100008     10.245.14.171/32

Input label database, 10.245.14.173:0-10.245.14.179:0
  Label     Prefix
 100001     10.245.14.171/32
 100002     10.245.14.173/32
      3     10.245.14.179/32
 100000     L2CKT VLAN VC 5

Output label database, 10.245.14.173:0-10.245.14.179:0
  Label     Prefix
 100009     10.245.14.179/32
      3     10.245.14.173/32
 100008     10.245.14.171/32
 100007     L2CKT VLAN VC 5

Router P0 Status


user@P0> show ldp database
Input label database, 10.245.14.171:0-10.245.14.173:0
  Label     Prefix
      3     10.245.14.173/32
 100009     10.245.14.179/32
 100008     10.245.14.171/32

Output label database, 10.245.14.171:0-10.245.14.173:0
  Label     Prefix
 100019     10.245.14.173/32
 100020     10.245.14.179/32
      3     10.245.14.171/32

Input label database, 10.245.14.171:0-10.245.14.179:0
  Label     Prefix
 100001     10.245.14.171/32
      3     10.245.14.179/32
 100002     10.245.14.173/32

Output label database, 10.245.14.171:0-10.245.14.179:0
  Label     Prefix
 100019     10.245.14.173/32
 100020     10.245.14.179/32
      3     10.245.14.171/32

Router PE2 Status


user@PE2> show l2circuit connections
Layer-2 Circuit Connections:

Legend for connection status (St)   Legend for interface status
EI -- encapsulation invalid         UP -- operational
MM -- mtu mismatch                  Dn -- down
EM -- encapsulation mismatch        NP -- no present
OL -- no outgoing label             DS -- disabled
Dn -- down                          WE -- wrong encapsulation
VC-Dn -- Virtual circuit Down       UN -- uninitialized
UP -- operational
XX -- unknown

Neighbor: 10.245.14.173
    Interface                 Type  St     Time last up          # Up trans
    fe-0/2/0.600 (vc 5)       rmt   Up     Nov 30 00:54:54 2001           1
      Local interface: fe-0/2/0.600, Status: Up,  Encapsulation: VLAN
      Remote PE: 10.245.14.173,  Negotiated control-word: Yes (Null)
      Incoming label: 100000, Outgoing label: 100007

user@PE2>  show ldp database

Input label database, 10.245.14.179:0-10.245.14.171:0
  Label     Prefix
 100019     10.245.14.173/32
      3     10.245.14.171/32
 100020     10.245.14.179/32

Output label database, 10.245.14.179:0-10.245.14.171:0
  Label     Prefix
 100001     10.245.14.171/32
 100002     10.245.14.173/32
      3     10.245.14.179/32

Input label database, 10.245.14.179:0-10.245.14.173:0
  Label     Prefix
      3     10.245.14.173/32
 100008     10.245.14.171/32
 100009     10.245.14.179/32
 100007     L2CKT VLAN VC 5

Output label database, 10.245.14.179:0-10.245.14.173:0
  Label     Prefix
 100001     10.245.14.171/32
 100002     10.245.14.173/32
      3     10.245.14.179/32
 100000     L2CKT VLAN VC 5

Published: 2010-04-15

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