25-4
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter25 Configuring MSDP
Configuring MSDP
Configuring MSDP
This section describes how to configure MSDP. It contains this configuration in for ma tion:
•Default MSDP Configuration, page 25-4
•Configuring a Default MSDP Peer, page 25-4 (required)
•Caching Source-Active State, page 25-6 (optional)
•Requesting Source Information from an MSDP Peer, page 25-8 (optional)
•Controlling Source Information that Your Switch Originates, page 25-8 (optional)
•Controlling Source Information that Your Switch Forwards, page 25-12 (optional)
•Controlling Source Information that Your Switch Receives, page 25-14 (optional)
•Configuring an MSDP Mesh Group, page 25-16 (optional)
•Shutting Down an MSDP Peer, page 25-16 (optional)
•Including a Bordering PIM Dense-Mode Region in MSDP, page 25-17 (optional)
•Configuring an Originating Address other than the RP Address, page 25-18 (optional)

Default MSDP Configuration

MSDP is not enabled, and no default MSDP peer exists.

Configuring a Default MSDP Peer

In this IOS release, because BGP and MBGP are not supported, you cannot configure an MSDP peer on
the local multilayer switch by using the ip msdp peer global configuration command. Instead, you
define a default MSDP peer (by using the ip msdp default-peer global configuration command) from
which to accept all SA messages for the multilayer switch. The default MSDP peer must be a previou sly
configured MSDP peer. Configure a default MSDP peer when the multilayer switch is not BGP- or
MBGP-peering with an MSDP peer. If a single MSDP peer is configured, the multilayer switch always
accepts all SA messages from that peer.
Figure 25-2 shows a network in which default MSDP peers might be used. In Figure 25-2, a customer
who owns Multilayer Switch B is connected to the Internet thr ough two In ter net servi ce pr ovide rs
(ISPs), one owning Router A and the other owning Router C. They are not running BGP or MBGP
between them. To learn about sources in the ISP’s domain or in other domains, multilayer Switch B at
the customer site identifies RouterA as its default MSDP peer. Multilayer Switch B advertises SA
messages to both Router A and Router C but accepts SA messages onl y f rom R oute r A or on ly R oute r
C. If Router A is first in the configuration file, it is used if it is running. If Rou ter A is not running, only
then does multilayer Switch B accept SA messages from Router C. This is the default behavior without
a prefix list.
If you specify a prefix list, the peer is a default peer only for the prefixes in the list. You can have
multiple active default peers when you have a prefix list asso ci at ed w it h ea ch . Whe n you do no t have
any prefix lists, you can configure multiple default peers, but only the first one is the active default peer
as long as the router has connectivity to this peer and the peer is alive. If the first configured peer fails
or the connectivity to this peer fails, the second conf igure d pee r b ecom es t he ac tive de faul t, an d so on.
The ISP probably uses a prefix list to define which prefixes it accepts from the customer’s router.