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Example: Layer 2 Circuit Traffic Engineering over Multiple LSPs Configuration

Figure 1: Layer 2 Circuit Traffic Engineering Topology Diagram

Figure 1 shows a network topology designed to traffic engineer different Layer 2 circuits over select LSPs. Across provider edge routers PE1 and PE2, an ATM AAL5 mode Layer 2 circuit connects customer edge routers CE1 and CE2, and a Frame Relay Layer 2 circuit connects routers CE3 and CE4. To maintain traffic separation, the ATM traffic is mapped onto LSP1 with a community named gold, and the Frame Relay traffic is mapped onto LSP2 with a community named silver. LSP1 takes the direct route between routers PE1 and PE2, while LSP2 travels from Router PE1 to PE2 through Router P0.

In addition to traffic engineering, you can send Layer 2 control information in the control word of a Layer 2 circuit. In this case, Frame Relay discard eligible (DE), forward explicit congestion notification (FECN), and backward explicit congestion notification (BECN) information is mapped into the control word. Likewise, ATM cell loss priority (CLP) and explicit forward congestion indicator (EFCI) information is mapped into the control word.

To traffic engineer Layer 2 circuits over multiple LSPs, you assign a set of Layer 2 circuits to a community and then apply a policy to send the community traffic over a desired LSP. To create communities, include the community community-name statement at the [edit policy-options] hierarchy level. To assign a Layer 2 circuit to a community, include the community community-name statement at the [edit protocols l2circuit neighbor neighbor-id interface interface-name] hierarchy level. To send community traffic over a specific LSP, include the community community-name statement at the [edit policy-options policy-statement policy-name term term-name from] hierarchy level and the install-next-hop lsp lsp-name statement at the [edit policy-options policy-statement policy-name term term-name then] hierarchy level.

On Router CE1, configure the ATM2 IQ interface at-0/0/1.32 to handle ATM AAL5 traffic:

On Router CE3, configure the SONET/SDH interface at so-0/0/1 to handle Frame Relay traffic:

On Router PE1, configure the ATM2 IQ-based CE1-facing interface at-1/1/0 with ATM VC multiplexing CCC encapsulation on the logical interface. Also enable the corresponding Layer 2 circuit modes at the [edit chassis] hierarchy level. In this case, you must configure AAL5 mode on PIC 1 in FPC 1. Once you configure the ATM2 IQ-based Layer 2 circuit, the CLP and EFCI bits are mapped to the control word by default.

Next, configure the Frame Relay interface so-1/1/1 with Frame Relay CCC encapsulation on both the physical and logical interface. Map the DE, FECN, and BECN bits to the control word with the translate-fecn-and-becn and translate-discard-eligible statements at the [edit interfaces so-fpc/pic/port unit unit-number family ccc] hierarchy level.

Establish your Layer 2 circuits 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 interfaces connected to the CE router, and a virtual circuit identifier for each VC. In this case, you will establish one VC for ATM AAL5 traffic and a second VC for Frame Relay traffic. Then, configure MPLS, LDP, and an IGP (such as OSPF) to enable signaling for your Layer 2 circuit. Two LSPs are established for the ATM and Frame Relay traffic: LSP1 for ATM traffic going directly to Router PE2 and LSP 2 for Frame Relay traffic going through Router P0 before going on to Router PE2.

Finally, configure a community for traffic separation for the ATM and Frame Relay Layer 2 circuits. Assign community goldto the ATM VC and community silver to the Frame Relay VC. Remember to give the communities numerical values and configure a routing policy to match the communities to specific LSPs. This policy is applied as an export policy for the forwarding table at the [edit routing-options] hierarchy level.

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. Only LSP 2 for Frame Relay passes through Router P0.

On Router PE2, complete the Layer 2 circuit by configuring statements to match those previously set on Router PE1.

Establish your Layer 2 circuits 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 interfaces connected to the CE router, and a virtual circuit identifier for each VC. In this case, you will establish one VC for ATM AAL5 traffic and a second VC for Frame Relay traffic. Then, configure MPLS, LDP, and an IGP (such as OSPF) to enable signaling for your Layer 2 circuit. Two LSPs are established for the ATM and Frame Relay traffic: LSP1 for ATM traffic going directly to Router PE2 and LSP 2 for Frame Relay traffic going through Router P0 before going on to Router PE2.

Finally, configure a community for traffic separation for the ATM and Frame Relay Layer 2 circuits. The ATM VC has community gold and the Frame Relay VC has community silver. Remember to give the communities numerical values and configure a routing policy to match the communities to specific LSPs. This policy is applied as an export policy for the forwarding table at the [edit routing-options] hierarchy level.

On Router CE2, configure the ATM2 IQ interfaces to handle ATM traffic. Interface at-1/0/1 handles AAL5 traffic.

On Router CE4, configure the SONET/SDH interface at so-1/1/2 to handle Frame Relay traffic:

Verifying Your Work

To verify proper operation of traffic engineered Layer 2 circuits, use the following command:

On Router PE1, you can see that ATM traffic is part of the gold community that has a value of 103:1 and is associated with LSP 1. Likewise, Frame Relay traffic is part of the silver community that has a value of 103:2 and is associated with LSP 2:

mpls.0: 2 destinations, 2 routes (2 active, 0 holddown, 0 hidden)
at-1/1/0.32  (1 entry, 1 announced)
          *L2CKT  Preference: 7
                  Next hop: 192.168.27.9 via so-1/1/0.0 weight 1, selected
                 Label-switched-path lsp1
                 Label operation: Push 100032 Offset: -4
                 Next hop: via so-0/0/1.0 weight 1
                 Label-switched-path lsp2
                 Label operation: Push 100032 Offset: -4
                 Protocol next hop: 10.255.17.4
                 Push 100032 Offset: -4
                  Indirect next hop: 8576bd0 300
                 State: <Active Int>
                 Age: 7:18
                 Task: Common L2 VC
                 Announcement bits (2): 0-KRT 1-Common L2 VC
                 AS path: I
                 Communities: 103:1 # This is the  gold  community.

so-1/1/1.512 (1 entry, 1 announced)
         *L2CKT  Preference: 7
                 Next hop: 192.168.27.9 via so-1/1/0.0 weight 1
                 Label-switched-path lsp1
                 Label operation: Push 100048 Offset: -4
                 Next hop: via so-0/0/1.0 weight 1, selected
                 Label-switched-path lsp2
                 Label operation: Push 100048 Offset: -4
                 Protocol next hop: 10.255.17.4
                 Push 100048 Offset: -4
                  Indirect next hop: 860f1f8 293
                 State: <Active Int>
                 Age: 5:15
                 Task: Common L2 VC
                 Announcement bits (2): 0-KRT 1-Common L2 VC
                 AS path: I
                 Communities: 103:2 # This is the  silver  community.