User`s guide

78 XSR User’s Guide
IP Routing Protocols Chapter 5
Configuring IP
 IP split horizon must be enabled (default). Whether poison is enabled
or not, triggered on demand will still send its updates with poison.
Triggered-on-demand RIP on the XSR is implemented by the following:

ip rip triggered-on-demand enables the functionality on a per
interface basis.

ip rip disable-triggered-updates, with the default enforced
(triggered updates enabled), invokes triggered updates in a timely
fashion as described by RFCs-1058 and 2453 (RIP and RIPv2
protocol). These commands work independently of each other.
NOTE
Triggered on demand operates on point-to-point Serial interfaces only.

ip rip max-retransmissions sets the number of retransmissions
to be sent.

ip rip polling-interval sets the polling period for triggered RIP
requests.
How Triggered-on-Demand RIP Works
To better understand when to configure triggered-on-demand RIP, consider
how it works. Routing updates are sent on the WAN in the following manner:
 The full content of the routing database is sent when:
– An update request has been received. The update is sent only to
the neighbor requesting it.
– The XSR is first powered up. The update is sent through all
interfaces running triggered-on-demand RIP.
– An interface is brought up. The update is sent only out the
interface which was brought up.
 A partial update of the database is sent when:
– An interface is brought up. The new local route is advertised to
all other interfaces running triggered-on-demand RIP.
– An interface is brought down. All routes reachable through the
interface that went down are advertised as unreachable to the
other interfaces running triggered-on-demand RIP.