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Example: Configuring Point-to-Multipoint LSPs with Static Routes

Understanding Point-to-Multipoint LSPs

A point-to-multipoint MPLS label-switched path (LSP) is an LDP-signaled or RSVP-signaled LSP with a single source and multiple destinations. By taking advantage of the MPLS packet replication capability of the network, point-to-multipoint LSPs avoid unnecessary packet replication at the inbound (ingress) router. Packet replication takes place only when packets are forwarded to two or more different destinations requiring different network paths.

This process is illustrated in Figure 1. Device PE1 is configured with a point-to-multipoint LSP to Routers PE2, PE3, and PE4. When Device PE1 sends a packet on the point-to-multipoint LSP to Routers P1 and P2, Device P1 replicates the packet and forwards it to Routers PE2 and PE3. Device P2 sends the packet to Device PE4.

Figure 1: Point-to-Multipoint LSPs

• A point-to-multipoint LSP allows you to use MPLS for point-to-multipoint data distribution. This functionality is similar to that provided by IP multicast.
• You can add and remove branch LSPs from a main point-to-multipoint LSP without disrupting traffic. The unaffected parts of the point-to-multipoint LSP continue to function normally.
• You can configure a node to be both a transit and an outbound (egress) router for different branch LSPs of the same point-to-multipoint LSP.
• You can enable link protection on a point-to-multipoint LSP. Link protection can provide a bypass LSP for each of the branch LSPs that make up the point-to-multipoint LSP. If any primary paths fail, traffic can be quickly switched to the bypass.
• You can configure subpaths either statically or dynamically.
• You can enable graceful restart on point-to-multipoint LSPs.

Point-to-Multipoint LSP Configuration Overview

1. Configure the primary LSP from the ingress router and the branch LSPs that carry traffic to the egress routers.
2. Specify a pathname on the primary LSP and this same path name on each branch LSP.

Note: By default, the branch LSPs are dynamically signaled by means of Constrained Shortest Path First (CSPF) and require no configuration. You can alternatively configure the branch LSPs as static paths.

Example: Configuring an RSVP-Signaled Point-to-Multipoint LSP

This example shows how to configure a collection of paths to create an RSVP-signaled point-to-multipoint label-switched path (LSP).

• Requirements
• Overview
• Configuration
• Verification

Requirements

In this example, no special configuration beyond device initialization is required.

Overview

In this example, multiple routing devices serve as the transit, branch, and leaf nodes of a single point-to-multipoint LSP. On the provider edge (PE), Device PE1 is the ingress node. The branches go from PE1 to PE2, PE1 to PE3, and PE1 to PE4. Static unicast routes on the ingress node (PE1) point to the egress nodes.

This example also demonstrates static routes with a next hop that is a point-to-multipoint LSP, using the p2mp-lsp-next-hop statement. This is useful when implementing filter-based forwarding.

Note: Another option is to use the lsp-next-hop statement to configure a regular point-to-point LSP to be the next hop. Though not shown in this example, you can optionally assign an independent preference and metric to the next hop.

Topology Diagram

Figure 2 shows the topology used in this example.

Figure 2: RSVP-Signaled Point-to-Multipoint LSP

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Configuring the Ingress Label-Switched Router (LSR) (Device PE1)

Step-by-Step Procedure

1. Configure the interfaces, interface encapsulation, and protocol families.

   [edit interfaces]user@PE1# set ge-2/0/2 unit 0 description PE1-to-CE1user@PE1# set ge-2/0/2 unit 0 family inet address 10.0.244.10/30user@PE1# set fe-2/0/10 unit 1 description PE1-to-P2user@PE1# set fe-2/0/10 unit 1 family inet address 2.2.2.1/24user@PE1# set fe-2/0/10 unit 1 family mplsuser@PE1# set fe-2/0/9 unit 8 description PE1-to-P3user@PE1# set fe-2/0/9 unit 8 family inet address 6.6.6.1/24user@PE1# set fe-2/0/9 unit 8 family mplsuser@PE1# set fe-2/0/8 unit 9 description PE1-to-P4user@PE1# set fe-2/0/8 unit 9 family inet address 3.3.3.1/24user@PE1# set fe-2/0/8 unit 9 family mplsuser@PE1# set lo0 unit 1 family inet address 100.10.10.10/32

2. Enable RSVP, MPLS, and OSPF on the interfaces.

   [edit protocols]user@PE1# set rsvp interface fe-2/0/10.1user@PE1# set rsvp interface fe-2/0/9.8user@PE1# set rsvp interface fe-2/0/8.9user@PE1# set rsvp interface lo0.1user@PE1# set mpls interface fe-2/0/10.1user@PE1# set mpls interface fe-2/0/9.8user@PE1# set mpls interface fe-2/0/8.9user@PE1# set mpls interface lo0.1user@PE1# set ospf area 0.0.0.0 interface ge-2/0/2.0user@PE1# set ospf area 0.0.0.0 interface fe-2/0/10.1user@PE1# set ospf area 0.0.0.0 interface fe-2/0/9.8user@PE1# set ospf area 0.0.0.0 interface fe-2/0/8.9user@PE1# set ospf area 0.0.0.0 interface lo0.1

3. Configure the MPLS point-to-multipoint LSPs.

   [edit protocols]user@PE1# set mpls label-switched-path PE1-PE2 to 100.50.50.50user@PE1# set mpls label-switched-path PE1-PE2 p2mp p2mp1user@PE1# set mpls label-switched-path PE1-PE3 to 100.70.70.70user@PE1# set mpls label-switched-path PE1-PE3 p2mp p2mp1user@PE1# set mpls label-switched-path PE1-PE4 to 100.40.40.40user@PE1# set mpls label-switched-path PE1-PE4 p2mp p2mp1
4. (Optional) Enable link protection on the LSPs.

   Link protection helps to ensure that traffic sent over a specific interface to a neighboring router can continue to reach the router if that interface fails.

   [edit protocols]user@PE1# set mpls label-switched-path PE1-PE2 link-protectionuser@PE1# set mpls label-switched-path PE1-PE3 link-protectionuser@PE1# set mpls label-switched-path PE1-PE4 link-protection

5. Enable MPLS to perform traffic engineering for OSPF.

   [edit protocols]user@PE1# set mpls traffic-engineering bgp-igp
   This causes the ingress routes to be installed in the inet.0 routing table. By default, MPLS performs traffic engineering for BGP only. You need to enable MPLS traffic engineering on the ingress LSR only.

6. Enable traffic engineering for OSPF.

   [edit protocols]user@PE1# set ospf traffic-engineering
   This causes the shortest-path first (SPF) algorithm to take into account the LSPs configured under MPLS.

7. Configure the router ID.

   [edit routing-options]user@PE1# set router-id 100.10.10.10

8. Configure static IP unicast routes with the point-to-multipoint LSP name as the next hop for each route.

   [edit routing-options]user@PE1# set static route 5.5.5.0/24p2mp-lsp-next-hop p2mp1user@PE1# set static route 7.7.7.0/24 p2mp-lsp-next-hop p2mp1user@PE1# set static route 4.4.4.0/24 p2mp-lsp-next-hop p2mp1

9. If you are done configuring the device, commit the configuration.

   [edit]user@PE1# commit

Configuring the Transit and Egress LSRs (Devices P2, P3, P4, PE2, PE3, and PE4)

Step-by-Step Procedure

1. Configure the interfaces, interface encapsulation, and protocol families.

   [edit]user@P2# set interfaces fe-2/0/10 unit 2 description P2-to-PE1user@P2# set interfaces fe-2/0/10 unit 2 family inet address 2.2.2.2/24user@P2# set interfaces fe-2/0/10 unit 2 family mplsuser@P2# set interfaces fe-2/0/9 unit 10 description P2-to-PE2user@P2# set interfaces fe-2/0/9 unit 10 family inet address 5.5.5.1/24user@P2# set interfaces fe-2/0/9 unit 10 family mplsuser@P2# set interfaces lo0 unit 2 family inet address 100.20.20.20/32user@PE2# set interfaces ge-2/0/3 unit 0 description PE2-to-CE2user@PE2# set interfaces ge-2/0/3 unit 0 family inet address 10.0.224.10/30user@PE2# set interfaces fe-2/0/10 unit 5 description PE2-to-P2user@PE2# set interfaces fe-2/0/10 unit 5 family inet address 5.5.5.2/24user@PE2# set interfaces fe-2/0/10 unit 5 family mplsuser@PE2# set interfaces lo0 unit 5 family inet address 100.50.50.50/32user@P3# set interfaces fe-2/0/10 unit 6 description P3-to-PE1user@P3# set interfaces fe-2/0/10 unit 6 family inet address 6.6.6.2/24user@P3# set interfaces fe-2/0/10 unit 6 family mplsuser@P3# set interfaces fe-2/0/9 unit 11 description P3-to-PE3user@P3# set interfaces fe-2/0/9 unit 11 family inet address 7.7.7.1/24user@P3# set interfaces fe-2/0/9 unit 11 family mplsuser@P3# set interfaces lo0 unit 6 family inet address 100.60.60.60/32user@PE3# set interfaces ge-2/0/1 unit 0 description PE3-to-CE3user@PE3# set interfaces ge-2/0/1 unit 0 family inet address 10.0.134.10/30user@PE3# set interfaces fe-2/0/10 unit 7 description PE3-to-P3user@PE3# set interfaces fe-2/0/10 unit 7 family inet address 7.7.7.2/24user@PE3# set interfaces fe-2/0/10 unit 7 family mplsuser@PE3# set interfaces lo0 unit 7 family inet address 100.70.70.70/32user@P4# set interfaces fe-2/0/10 unit 3 description P4-to-PE1user@P4# set interfaces fe-2/0/10 unit 3 family inet address 3.3.3.2/24user@P4# set interfaces fe-2/0/10 unit 3 family mplsuser@P4# set interfaces fe-2/0/9 unit 12 description P4-to-PE4user@P4# set interfaces fe-2/0/9 unit 12 family inet address 4.4.4.1/24user@P4# set interfaces fe-2/0/9 unit 12 family mplsuser@P4# set interfaces lo0 unit 3 family inet address 100.30.30.30/32user@PE4# set interfaces ge-2/0/0 unit 0 description PE4-to-CE4user@PE4# set interfaces ge-2/0/0 unit 0 family inet address 10.0.104.9/30user@PE4# set interfaces fe-2/0/10 unit 4 description PE4-to-P4user@PE4# set interfaces fe-2/0/10 unit 4 family inet address 4.4.4.2/24user@PE4# set interfaces fe-2/0/10 unit 4 family mplsuser@PE4# set interfaces lo0 unit 4 family inet address 100.40.40.40/32

2. Enable RSVP, MPLS, and OSPF on the interfaces.

   [edit]user@P2# set protocols rsvp interface fe-2/0/10.2user@P2# set protocols rsvp interface fe-2/0/9.10user@P2# set protocols rsvp interface lo0.2user@P2# set protocols mpls interface fe-2/0/10.2user@P2# set protocols mpls interface fe-2/0/9.10user@P2# set protocols mpls interface lo0.2user@P2# set protocols ospf area 0.0.0.0 interface fe-2/0/10.2user@P2# set protocols ospf area 0.0.0.0 interface fe-2/0/9.10user@P2# set protocols ospf area 0.0.0.0 interface lo0.2user@PE2# set protocols rsvp interface fe-2/0/10.5user@PE2# set protocols rsvp interface lo0.5user@PE2# set protocols mpls interface fe-2/0/10.5user@PE2# set protocols mpls interface lo0.5user@PE2# set protocols ospf area 0.0.0.0 interface ge-2/0/3.0user@PE2# set protocols ospf area 0.0.0.0 interface fe-2/0/10.5user@PE2# set protocols ospf area 0.0.0.0 interface lo0.5user@P3# set protocols rsvp interface fe-2/0/10.6user@P3# set protocols rsvp interface fe-2/0/9.11user@P3# set protocols rsvp interface lo0.6user@P3# set protocols mpls interface fe-2/0/10.6user@P3# set protocols mpls interface fe-2/0/9.11user@P3# set protocols mpls interface lo0.6user@P3# set protocols ospf area 0.0.0.0 interface fe-2/0/10.6user@P3# set protocols ospf area 0.0.0.0 interface fe-2/0/9.11user@P3# set protocols ospf area 0.0.0.0 interface lo0.6user@PE3# set protocols rsvp interface fe-2/0/10.7user@PE3# set protocols rsvp interface lo0.7user@PE3# set protocols mpls interface fe-2/0/10.7user@PE3# set protocols mpls interface lo0.7user@PE3# set protocols ospf area 0.0.0.0 interface ge-2/0/1.0user@PE3# set protocols ospf area 0.0.0.0 interface fe-2/0/10.7user@PE3# set protocols ospf area 0.0.0.0 interface lo0.7user@P4# set protocols rsvp interface fe-2/0/10.3user@P4# set protocols rsvp interface fe-2/0/9.12user@P4# set protocols rsvp interface lo0.3user@P4# set protocols mpls interface fe-2/0/10.3user@P4# set protocols mpls interface fe-2/0/9.12user@P4# set protocols mpls interface lo0.3user@P4# set protocols ospf area 0.0.0.0 interface fe-2/0/10.3user@P4# set protocols ospf area 0.0.0.0 interface fe-2/0/9.12user@P4# set protocols ospf area 0.0.0.0 interface lo0.3user@PE4# set protocols rsvp interface fe-2/0/10.4user@PE4# set protocols rsvp interface lo0.4user@PE4# set protocols mpls interface fe-2/0/10.4user@PE4# set protocols mpls interface lo0.4user@PE4# set protocols ospf area 0.0.0.0 interface ge-2/0/0.0user@PE4# set protocols ospf area 0.0.0.0 interface fe-2/0/10.4user@PE4# set protocols ospf area 0.0.0.0 interface lo0.4

3. Enable traffic engineering for OSPF.

   [edit]user@P2# set protocols ospf traffic-engineeringuser@P2# set protocols ospf traffic-engineeringuser@P3# set protocols ospf traffic-engineeringuser@PE2# set protocols ospf traffic-engineeringuser@PE3# set protocols ospf traffic-engineeringuser@PE4# set protocols ospf traffic-engineering
   This causes the shortest-path first (SPF) algorithm to take into account the LSPs configured under MPLS.

4. Configure the router IDs.

   [edit]user@P2# set routing-options router-id 100.20.20.20user@P3# set routing-options router-id 100.60.60.60user@P4# set routing-options router-id 100.30.30.30user@PE2# set routing-options router-id 100.50.50.50user@PE3# set routing-options router-id 100.70.70.70user@PE4# set routing-options router-id 100.40.40.40

5. If you are done configuring the devices, commit the configuration.

   [edit]user@host# commit

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configuring Device CE1

Step-by-Step Procedure

1. Configure an interface to Device PE1.

   [edit interfaces]user@CE1# set ge-1/3/2 unit 0 family inet address 10.0.244.9/30user@CE1# set ge-1/3/2 unit 0 description CE1-to-PE1

2. Configure static routes from Device CE1 to the three other customer networks, with Device PE1 as the next hop.

   [edit routing-options]user@CE1# set static route 10.0.104.8/30 next-hop 10.0.244.10user@CE1# set static route 10.0.134.8/30 next-hop 10.0.244.10user@CE1# set static route 10.0.224.8/30 next-hop 10.0.244.10

3. If you are done configuring the device, commit the configuration.

   [edit]user@CE1# commit

Results

From configuration mode, confirm your configuration by entering the show interfaces and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configuring Device CE2

Step-by-Step Procedure

1. Configure an interface to Device PE2.

   [edit interfaces]user@CE2# set ge-1/3/3 unit 0 family inet address 10.0.224.9/30 user@CE2# set ge-1/3/3 unit 0 description CE2-to-PE2

2. Configure a static route from Device CE2 to CE1, with Device PE2 as the next hop.

   [edit routing-options]user@CE2# set static route 10.0.244.8/30 next-hop 10.0.224.10

3. If you are done configuring the device, commit the configuration.

   [edit]user@CE2# commit

Results

From configuration mode, confirm your configuration by entering the show interfaces and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configuring Device CE3

Step-by-Step Procedure

1. Configure an interface to Device PE3.

   [edit interfaces]user@CE3# set ge-2/0/1 unit 0 family inet address 10.0.134.9/30 user@CE3# set ge-2/0/1 unit 0 description CE3-to-PE3

2. Configure a static route from Device CE3 to CE1, with Device PE3 as the next hop.

   [edit routing-options]user@CE3# set static route 10.0.244.8/30 next-hop 10.0.134.10

3. If you are done configuring the device, commit the configuration.

   [edit]user@CE3# commit

Results

From configuration mode, confirm your configuration by entering the show interfaces and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Configuring Device CE4

Step-by-Step Procedure

1. Configure an interface to Device PE4.

   [edit interfaces]user@CE4# set ge-3/1/3 unit 0 family inet address 10.0.104.10/30 user@CE4# set ge-3/1/3 unit 0 description CE4-to-PE4

2. Configure a static route from Device CE4 to CE1, with Device PE4 as the next hop.

   [edit routing-options]user@CE4# set static route 10.0.244.8/30 next-hop 10.0.104.9

3. If you are done configuring the device, commit the configuration.

   [edit]user@CE4# commit

Results

From configuration mode, confirm your configuration by entering the show interfaces and show routing-options commands. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

Verification

Confirm that the configuration is working properly.

• Verifying Connectivity
• Verifying the State of the Point-to-Multipoint LSP
• Checking the Forwarding Table

Verifying Connectivity

Purpose

Make sure that the devices can ping each other.

Action

PING 10.0.224.9 (10.0.224.9): 56 data bytes
64 bytes from 10.0.224.9: icmp_seq=0 ttl=61 time=1.387 ms
64 bytes from 10.0.224.9: icmp_seq=1 ttl=61 time=1.394 ms
64 bytes from 10.0.224.9: icmp_seq=2 ttl=61 time=1.506 ms
^C
--- 10.0.224.9 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 1.387/1.429/1.506/0.055 ms

PING 10.0.134.9 (10.0.134.9): 56 data bytes
64 bytes from 10.0.134.9: icmp_seq=0 ttl=61 time=1.068 ms
64 bytes from 10.0.134.9: icmp_seq=1 ttl=61 time=1.062 ms
64 bytes from 10.0.134.9: icmp_seq=2 ttl=61 time=1.053 ms
^C
--- 10.0.134.9 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 1.053/1.061/1.068/0.006 ms

PING 10.0.104.10 (10.0.104.10): 56 data bytes
64 bytes from 10.0.104.10: icmp_seq=0 ttl=61 time=1.079 ms
64 bytes from 10.0.104.10: icmp_seq=1 ttl=61 time=1.048 ms
64 bytes from 10.0.104.10: icmp_seq=2 ttl=61 time=1.070 ms
^C
--- 10.0.104.10 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/stddev = 1.048/1.066/1.079/0.013 ms

Verifying the State of the Point-to-Multipoint LSP

Purpose

Make sure that the ingress, transit, and egress LSRs are in the Up state.

Action

Ingress LSP: 1 sessions
P2MP name: p2mp1, P2MP branch count: 3
To              From            State Rt P     ActivePath       LSPname
100.40.40.40    100.10.10.10    Up     0 *                      PE1-PE4
100.70.70.70    100.10.10.10    Up     0 *                      PE1-PE3
100.50.50.50    100.10.10.10    Up     0 *                      PE1-PE2
Total 3 displayed, Up 3, Down 0
...

Checking the Forwarding Table

Purpose

Make sure that the routes are set up as expected by running the show route forwarding-table command. Only the routes to the remote customer networks are shown here.

Action

Routing table: default.inet
Internet:
Destination        Type RtRef Next hop           Type Index NhRef Netif
...
10.0.104.8/30      user     0 3.3.3.2            ucst  1006     6 fe-2/0/8.9
10.0.134.8/30      user     0 6.6.6.2            ucst  1010     6 fe-2/0/9.8
10.0.224.8/30      user     0 2.2.2.2            ucst  1008     6 fe-2/0/10.1
...