Dvmrp Policies - Avaya 8800 Planning And Engineering, Network Design

• Do not use low timer values, especially low route update timers because this can result in a
high CPU load: the CPU must process frequent messages. Also, setting lower timer values,
such as those for the route-switch timeout, can result in a flapping condition in cases where
routes time out very quickly.
• Follow the DVMRP standard (RFC 1075) with respect to the relationship between correlated
timers. For example, the Route Hold-down equals twice the Route Report Interval.

DVMRP policies

DVMRP policies include announce and accept, do not advertise self, and default route policies. By
filtering routes that are not necessary to advertise, you can use policies to scale to very large
DVMRP networks.
Announce and accept policy examples
By using accept or announce policies, you can filter out subnets that only have multicast receivers
without impacting the ability to deliver streams to those subnets.
The following figure shows an example of a network boundary router that connects a public
multicast network to a private multicast network. Both networks contain multicast sources and use
DVMRP for routing. The goal is to receive and distribute public multicast streams on the private
network, while not forwarding private multicast streams to the public network.
Given the topology, an appropriate solution is to use an announce policy on the public network
interface of Router A. This prevents the public network from receiving the private multicast streams,
while allowing Router A to still act as a transit router within the private network. Public multicast
streams are forwarded to the private network as desired.
Figure 87: Announce policy on a border router
The following figure illustrates a similar scenario. As before, the goal is to receive and distribute
public multicast streams on the private network, while not forwarding private multicast streams to the
June 2016
Distance Vector Multicast Routing Protocol guidelines
Planning and Engineering — Network Design
Comments on this document? infodev@avaya.com
193