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Example: Interconnecting a Layer 2 Circuit with a Layer 2 VPN
This example provides a step-by-step procedure and commands for configuring and verifying a Layer 2 circuit to a Layer 2 VPN. 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 3D Universal Edge Routers
- 2 M Series Multiservice Edge Router
- 1 T Series Core Router
- 1 EX Series Ethernet Switch
- 1 J Series Services Routers
Overview and Topology
The physical topology of a Layer 2 circuit to a Layer 2 VPN connection is shown in Figure 1.
Figure 1: Physical Topology of a Layer 2 Circuit to a Layer 2 VPN Connection

The logical topology of a Layer 2 circuit to a Layer 2 VPN connection is shown in Figure 2.
Figure 2: Logical Topology of a Layer 2 Circuit to a Layer 2 VPN Connection

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:
- CE1 identifies the customer edge 1 (CE1) 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 is organized in the following sections:
Configuring Protocols on the PE and P Routers
Step-by-Step Procedure
In this example, all of the PE routers and P routers are configured with OSPF as the IGP protocol. The MPLS, LDP, and BGP protocols are enabled on all of the interfaces except fxp.0. Core-facing interfaces are enabled with the MPLS address and inet address.
- Configure all the PE and P routers with OSPF as the IGP.
Enable the MPLS, LDP, and BGP 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;}}bgp {group RR {type internal;local-address 1.1.1.1;family l2vpn {signaling;}neighbor 7.7.7.7;}}ospf {traffic-engineering;area 0.0.0.0 {interface all;interface fxp0.0 {disable;}}}ldp {interface all;interface fxp0.0 {disable;}}}
- Configure the PE and P routers with OSPF as the IGP. Enable
the MPLS, LDP, and BGP protocols on all interfaces except fxp.0. BGP is used as the signaling protocol on Router PE3 for the Layer
2 VPN. The following configuration snippet shows the protocol configuration
for Router PE3: [edit]protocols {mpls {interface all;interface fxp0.0 {disable;}}bgp {group RR {type internal;local-address 3.3.3.3;family l2vpn {signaling;}neighbor 7.7.7.7;}}ospf {traffic-engineering;area 0.0.0.0 {interface all;interface fxp0.0 {disable;}}}ldp {interface all;interface fxp0.0 {disable;}}}
Step-by-Step Procedure
Configuring Interfaces
- 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.
The encapsulation should be configured the same way for all routers
in the Layer 2 circuit domain.[edit interfaces]ge-1/0/0 {encapsulation ethernet-ccc;unit 0 {family ccc;}}lo0 {unit 0 {family inet {address 1.1.1.1/32;}}}
- Router PE5 is the router that is stitching the Layer 2 circuit to the Layer 2 VPN using the interworking interface.
The configuration of the peer unit interfaces is what makes the interconnection.
On Router PE5, configure the iw0 interface with two logical interfaces. To configure the iw0 interface, include the interfaces statement and specify iw0 as the interface name. For the unit 0 logical interface, include the peer-unit statement and specify the logical interface unit 1 as the peer interface. For the unit 1 logical interface, include the peer-unit statement and specify the logical interface unit 0 as the peer interface.
[edit interfaces]iw0 {unit 0 {encapsulation ethernet-ccc;peer-unit 1;}unit 1 {encapsulation ethernet-ccc;peer-unit 0;}} - On Router PE5, 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 5.5.5.5/32;}}}
Step-by-Step Procedure
Configuring the Layer 2 circuit protocol
- On Router PE1, configure the IP address of the remote
PE router with the neighbor statement. The loopback address
and router ID of the PE neighbor is commonly the neighbor’s
IP address. To allow a Layer 2 circuit to be established even though
the maximum transmission unit (MTU) configured on the PE router does
not match the MTU configured on the remote PE router, include the ignore-mtu-mismatch statement.[edit]protocols {l2circuit {neighbor 5.5.5.5 {interface ge-1/0/0.0 {virtual-circuit-id 100;no-control-word;ignore-mtu-mismatch;}}}}
- On Router PE5, configure the IP address of the remote
PE router. To configure the IP address of the remote PE router, include
the neighbor statement and specify the IP address of the
loopback interface on Router PE1. Configure the virtual circuit ID
to be the same as the virtual circuit ID on the neighbor router. 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, include the ignore-mtu-mismatch statement. Also
disable the use of the control word for demultiplexing by including
the no-control-word statement. [edit protocols]l2circuit {neighbor 1.1.1.1 {interface iw0.0 {virtual-circuit-id 100;no-control-word;ignore-mtu-mismatch;}}}
- On Router PE5, configure the Layer 2 VPN protocols by
including the l2vpn statement at the [edit routing-instances routing-instances-name protocols] hierarchy level.
To configure the iw0 interface, include the interfaces statement and specify iw0 as the interface name. The iw0 interface is configured under the Layer 2 VPN protocols
to receive the looped packet from the iw0.1 logical interface.
The l2vpn protocol is configured on Router PE5 with site
CE5, which is configured in the BGP L2VPN routing instance. Router
CE1 has communication to Router CE5, through the Layer 2 interworking
configuration on Router PE5.[edit]routing-instances {L2VPN {instance-type l2vpn;interface ge-2/0/0.0;interface iw0.1;route-distinguisher 65000:5;vrf-target target:65000:2;protocols {l2vpn {encapsulation-type ethernet;site CE5 {site-identifier 5;interface ge-2/0/0.0 {remote-site-id 3;}}site l2-circuit {site-identifier 6;interface iw0.1 {remote-site-id 3;}}}}}}
- In addition to the iw0 interface configuration,
the Layer 2 interworking l2iw protocol must be configured.
Without the l2iw protocol configuration, the Layer 2 interworking
routes are not formed, regardless of whether any iw interfaces
are present.
On Router PE5, configure the l2iw protocol. To configure the protocol, include the l2iw statement at the [edit protocols] hierarchy level.
[edit]protocols {l2iw;}
Verification
Step-by-Step Procedure
Verifying the Layer 2 Circuit Connection on Router PE1.
- On Router PE1, use the show l2circuit connections command to verify that the Layer 2 Circuit from Router PE1 to Router
PE5 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: 5.5.5.5 Interface Type St Time last up # Up trans ge-1/0/0.0(vc 100) rmt Up Jan 3 22:00:49 2010 1 Remote PE: 5.5.5.5, Negotiated control-word: No Incoming label: 301328, Outgoing label: 300192 Local interface: ge-1/0/0.0, Status: Up, Encapsulation: ETHERNET
- On Router PE5, use the show l2vpn connections command to verify that the Layer 2 VPN connection is Up using the iw0 peer interface of the Layer 2 circuit.
user@PE5> show l2vpn connections
Instance: L2VPN Local site: CE5 (5) connection-site Type St Time last up # Up trans l2-circuit (6) loc OR 3 rmt Up Jan 3 22:51:12 2010 1 Remote PE: 3.3.3.3, Negotiated control-word: Yes (Null) Incoming label: 800258, Outgoing label: 800000 Local interface: ge-2/0/0.0, Status: Up, Encapsulation: ETHERNET Local site: l2-circuit (6) connection-site Type St Time last up # Up trans CE5 (5) loc OR 3 rmt Up Jan 3 22:56:38 2010 1 Remote PE: 3.3.3.3, Negotiated control-word: Yes (Null) Incoming label: 800262, Outgoing label: 800001 Local interface: iw0.1, Status: Up, Encapsulation: ETHERNET
Step-by-Step Procedure
Verifying that the Layer 2 Circuit is terminating into the Layer 2 VPN connection.
- On Router PE5, use the show l2circuit connections command to verify that the Layer 2 circuit is Up using
the iw0 interface. This will be looped through the iwo.1 interface to the Layer 2 VPN.
user@PE5> show l2circuit connections
Layer-2 Circuit Connections: Neighbor: 1.1.1.1 Interface Type St Time last up # Up trans iw0.0(vc 100) rmt Up Jan 3 21:59:07 2010 1 Remote PE: 1.1.1.1, Negotiated control-word: No Incoming label: 300192, Outgoing label: 301328
- On Router PE 5, use the show route table mpls.0 command to verify the Layer 2 circuit and Layer 2 VPN routes. In
the example below, the Layer 2 circuit is associated with LDP label 301328 and the Layer 2 VPN is associated with LDP label 800001. Notice the two iw0 interfaces that are used
for the Layer 2 interworking route.
user@PE5>show route table mpls.0
mpls.0: 18 destinations, 20 routes (18 active, 2 holddown, 0 hidden) + = Active Route, - = Last Active, * = Both 0 *[MPLS/0] 5d 20:07:31, metric 1 Receive 1 *[MPLS/0] 5d 20:07:31, metric 1 Receive 2 *[MPLS/0] 5d 20:07:31, metric 1 Receive 299776 *[LDP/9] 2d 03:00:51, metric 1 300048 *[LDP/9] 2d 03:00:49, metric 1 > to 10.10.6.1 via xe-0/1/0.0, Pop 300048(S=0) *[LDP/9] 2d 03:00:49, metric 1 > to 10.10.6.1 via xe-0/1/0.0, Pop 300192 *[L2IW/6] 19:11:05, metric2 1 > to 10.10.6.1 via xe-0/1/0.0, Swap 800001 [L2CKT/7] 20:08:36 > via iw0.0, Pop 800258 *[L2VPN/7] 19:16:31 > via ge-2/0/0.0, Pop Offset: 4 800262 *[L2IW/6] 19:11:05, metric2 1 > to 10.10.3.1 via xe-1/1/0.0, Swap 301328 [L2VPN/7] 19:11:05 > via iw0.1, Pop Offset: 4ge-2/0/0.0 *[L2VPN/7] 19:16:31, metric2 1 > to 10.10.6.1 via xe-0/1/0.0, Push 800000 Offset: -4 iw0.0 *[L2CKT/7] 20:08:36, metric2 1 > to 10.10.3.1 via xe-1/1/0.0, Push 301328 iw0.1 *[L2VPN/7] 19:11:05, metric2 1 > to 10.10.6.1 via xe-0/1/0.0, Push 800001 Offset: -4