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Example: SONET/SDH-Based Layer 2 Circuit Configuration

Figure 26: SONET/SDH-Based Layer 2 Circuit Topology Diagram

Image g017216.gif

In this second Layer 2 circuit example shown in Figure 26, you configure a Layer 2 circuit for a SONET/SDH interface encapsulated with PPP.

On Router CE1, configure the SONET/SDH interface to handle PPP traffic. Be sure to use the same IP address prefix both here and on the SONET/SDH interface of Router CE2.

Router CE1

[edit]
interfaces {
so-0/0/1 {
description "to PE1 so-0/0/0";
encapsulation ppp;
unit 0 {
family inet {
address 10.1.1.1/30;
}
}
}
}

On Router PE1, configure the PPP-based CE-facing interface with PPP CCC encapsulation. 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-0/0/0 {
description "to CE1 so-0/0/1";
encapsulation ppp-ccc; # Configure CCC encapsulation on CE-facing interfaces.
unit 0;
}
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.
}
}
lo0 {
unit 0 {
family inet {
address 10.255.145.126/32;
}
}
}
}
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;
}
l2circuit {
neighbor 10.255.145.130 { # This points to the loopback of the PE neighbor.
interface so-0/0/0.0 { # Here you include the local CE-facing interface.
virtual-circuit-id 1; # 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.
}
}
so-0/2/1 {
description "to PE2 so-1/1/0";
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 10.255.145.129/32;
}
}
}
}
protocols {
ospf {
traffic-engineering;
area 0.0.0.0 {
interface so-0/0/0.0;
interface so-0/2/1.0;
}
}
ldp { # LDP is required as the signaling protocol for Layer 2 circuits.
interface so-0/0/0.0;
interface so-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 PPP-based CE-facing interface with PPP CCC encapsulation. Complete 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 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 PE2

[edit]
interfaces {
so-1/0/0 {
description "to CE1 so-1/0/1";
encapsulation ppp-ccc; # Configure CCC encapsulation on CE-facing interfaces.
unit 0;
}
so-1/1/0 {
description "to P0 so-0/2/1";
unit 0 {
family inet {
address 192.168.245.18/30;
}
family mpls; # Include the MPLS family on core-facing interfaces.
}
}
lo0 {
unit 0 {
family inet {
address 10.255.145.130/32;
}
}
}
}
protocols {
ospf {
traffic-engineering;
area 0.0.0.0 {
interface so-1/1/0.0;
interface lo0.0;
}
}
ldp { # LDP is required as the signaling protocol for Layer 2 circuits.
interface so-1/1/0.0;
interface lo0.0;
}
l2circuit {
neighbor 10.255.145.126 { # This points to the loopback of the PE neighbor.
interface so-1/0/0.0 { # Here you include the local CE-facing interface.
virtual-circuit-id 1; # Be sure this ID matches the ID of your PE neighbor.
}
}
}
}

On Router CE2, configure the SONET/SDH interface to handle PPP traffic. Be sure to use the same IP address prefix both here and on the SONET/SDH interface of Router CE1.

Router CE2

[edit]
interfaces {
so-1/0/1 {
description "to PE2 so-1/0/0";
encapsulation ppp;
unit 0 {
family inet {
address 10.1.1.2/30;
}
}
}
}

Verifying Your Work

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

The following section shows the output of these commands used with the configuration example:


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

Legend for connection status (St)
EI -- encapsulation invalid      NP -- interface not present
MM -- mtu mismatch               Dn -- down
EM -- encapsulation mismatch     VC-Dn -- Virtual circuit Down
CM -- control-word mismatch      Up -- operational
OL -- no outgoing label          XX -- unknown
NC -- intf encaps not CCC/TCC

Legend for interface status
Up -- operational
Dn -- down

Neighbor: 10.255.145.130
     Interface                 Type  St     Time last up          # Up trans
     so-0/0/0.0 (vc 1)         rmt   Up     Jan 26 14:13:54 2003           1
       Local interface: so-0/0/0.0, Status: Up, Encapsulation: PPP
       Remote PE: 10.255.145.130, Negotiated control-word: Yes (Null)
       Incoming label: 100000, Outgoing label: 100000

user@PE1>  show ldp database l2circuit
Input label database, 10.255.145.126:0--10.255.145.130:0
   Label     Prefix
  100000     L2CKT CtrlWord PPP VC 1

Output label database, 10.255.145.126:0--10.255.145.130:0
   Label     Prefix
  100000     L2CKT CtrlWord PPP VC 1

user@PE1> show ldp database l2circuit detail
Input label database, 10.255.145.126:0--10.255.145.130:0
   Label     Prefix
  100000     L2CKT CtrlWord PPP VC 1
             State: Active
             Age: 5:37

Output label database, 10.255.145.126:0--10.255.145.130:0
   Label     Prefix
  100000     L2CKT CtrlWord PPP VC 1
             State: Active
             Age: 5:37

user@PE1> show route table mpls.0

mpls.0: 7 destinations, 7 routes (7 active, 0 holddown, 0 hidden)
Restart Complete
+ = Active Route, - = Last Active, * = Both
0                  *[MPLS/0] 00:05:04, metric 1
                       Receive
1                  *[MPLS/0] 00:05:04, metric 1
                       Receive
2                  *[MPLS/0] 00:05:04, metric 1
                       Receive
100000             *[L2VPN/7] 00:04:50
                     > via so-0/0/0.0, Pop       Offset: 4
100016             *[LDP/9] 00:04:52, metric 1
                     > via so-0/1/0.0, Pop
100016(S=0)        *[LDP/9] 00:04:52, metric 1
                     > via so-0/1/0.0, Pop
so-0/0/0.0         *[L2VPN/7] 00:04:50
                     > via so-0/1/0.0, Push 100000 Offset: -4
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