47-4
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter47 Configuring MSDP
Configuring MSDP
•Controlling Source Information that Your Switch Originates, page47-8 (optional)
•Controlling Source Information that Your Switch Forwards, page47-11 (optional)
•Controlling Source Information that Your Switch Receives, page47-13 (optional)
•Configuring an MSDP Mesh Group, page47-15 (optional)
•Shutting Down an MSDP Peer, page47-15 (optional)
•Including a Bordering PIM Dense-Mode Region in MSDP, page47-16 (optional)
•Configuring an Originating Address other than the RP Address, page47-17 (optional)
Default MSDP Configuration
MSDP is not enabled, and no default MSDP peer exists.
Configuring a Default MSDP Peer
In this software release, because BGP and MBGP are not supported, you cannot configure an MSDP peer
on the local 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 switch. The default MSDP peer must be a previously configured MSDP
peer. Configure a default MSDP peer when the switch is not BGP- or MBGP-peering with an MSDP
peer. If a single MSDP peer is configured, the switch always accepts all SA messages from that peer.
Figure 47-2 shows a network in which default MSDP peers might be used. In Figure 47-2, a customer
who owns Switch B is connected to the Internet through two Internet service providers (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, Switch B at the customer site identifies
Router A as its default MSDP peer. Switch B advertises SA messages to both Router A and Router C but
accepts SA messages only from Router A or only from Router C. If Router A is first in the configuration
file, it is used if it is running. If Router A is not running, only then does 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 associated with each. When you do not 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 configured peer becomes the active default, and so on.
The ISP probably uses a prefix list to define which prefixes it accepts from the customer’s router.