Flooding Unknown Traffic Using Point-to-Multipoint LSPs in VPLS

For a VPLS routing instance, you can flood unknown unicast, broadcast, and multicast traffic using point-to-multipoint (also called P2MP) LSPs. By default, VPLS relies upon ingress replication to flood unknown traffic to the members of a VPLS routing instance. This can cause replication of data at routing nodes shared by multiple VPLS members, as shown in Figure 1. The flood data is tripled between PE router PE1 and provider router P1 and doubled between provider routers P1 and P2. By configuring point-to-multipoint LSPs to handle flood traffic, the VPLS routing instance can avoid this type of traffic replication in the network, as shown in Figure 2.

Figure 1: Flooding Unknown VPLS Traffic Using Ingress Replication

Figure 2: Flooding Unknown VPLS Traffic Using a Point-to-Multipoint LSP

The point-to-multipoint LSP used for VPLS flooding can be either static or dynamic. In either case, for each VPLS routing instance, the PE router creates a dedicated point-to-multipoint LSP. All of the neighbors of the VPLS routing instance are added to the point-to-multipoint LSP when the feature is enabled. If there are n PE routers in the VPLS routing instance, n point-to-multipoint LSPs are created in the network where each PE router is the root of the point-to-multipoint tree and includes the rest of the n – 1 PE routers as leaf nodes. If you configured static point-to-multipoint LSPs for flooding, any additional VPLS neighbors added to the routing instance later are not automatically added to the point-to-multipoint LSP. You will need to manually add the new VPLS neighbors to the static point-to-multipoint flooding LSP. If you configure dynamic point-to-multipoint LSPs, whenever VPLS discovers a new neighbor through BGP, a sub-LSP for this neighbor is added to the point-to-multipoint LSP for the routing instance.

This feature can be enabled incrementally on any PE router that is part of a specific VPLS routing instance. The PE routers can then use point-to-multipoint LSPs to flood traffic, whereas other PE routers in the same VPLS routing instance can still use ingress replication to flood traffic. However, when this feature is enabled on any PE router, you must ensure that all PE routers in the VPLS routing instance that participate in the flooding of traffic over point-to-multipoint LSPs are upgraded to Junos OS Release 8.3 or later to support this feature.

To flood unknown unicast, broadcast, and multicast traffic using point-to-multipoint LSPs, configure the rsvp-te statement as follows:

rsvp-te {
    label-switched-path-template (Multicast) {
        (default-template | lsp-template-name);
    }
    static-lsp lsp-name;
}

You can include this statement at the following hierarchy levels:

• [edit routing-instance routing-instance-name provider-tunnel]

• [edit logical-systems logical-system-name routing-instances routing-instance-name provider-tunnel]

You can configure either a static point-to-multipoint LSP for VPLS flooding or a dynamic point-to-multipoint LSP.

The following sections describe how to configure static and dynamic point-to-multipoint LSPs for flooding unknown traffic in a VPLS routing instance:

static-lsp lsp-name;

[edit routing-instances routing-instance-name provider-tunnel rsvp-te]
label-switched-path-template (Multicast) {
    (default-template | lsp-template-name);
}

user@host> show mpls lsp p2mp ingress 
Ingress LSP: 2 sessions P2MP name: static, P2MP branch count: 3
To              From            State Rt ActivePath       P     LSPname
10.255.14.181   10.255.14.172   Up     0                  *     vpn02-vpn11
10.255.14.177   10.255.14.172   Up     0 path2            *     vpn02-vpn07
10.255.14.174   10.255.14.172   Up     0 path3            *     vpn02-vpn04
P2MP name: 9:vpls:10.255.14.172:green, P2MP branch count: 2
To              From            State Rt ActivePath       P     LSPname
10.255.14.177   10.255.14.172   Up     0                  *     11:vpls:10.255.14.172:green
10.255.14.174   10.255.14.172   Up     0                  *     10:vpls:10.255.14.172:green
Total 5 displayed, Up 5, Down 0

p2mp;
template;

label-switched-path-template (Multicast) p2mp-lsp-template-name;