# Exchanging DVMRP Unicast Routes

DVMRP maintains its own unicast routing table, based on distance vector calculations. The routing table defines the best-known distance to each destination and how to get there. The router updates the table by exchanging information with its neighbors. The DVMRP routing table is used solely for RPF lookups.

By default, if DVMRP owns an interface, that interface exchanges DVMRP unicast routes with its neighbors, and you cannot disable the exchange of routes. However, you can enable and disable the exchange of DVMRP unicast routes on interfaces that DVMRP does not own.

When an interface exchanges DVMRP routes, the router obtains routes from DVMRP report messages and stores them in its DVMRP routing table. Other multicast protocols, such as PIM, can then use these routes for RPF lookups. With this feature, PIM can use the DVMRP routing table even when the router is not running DVMRP.

All interfaces, including tunnels, support DVMRP unicast routing. DVMRP tunnels use DVMRP multicast routing to support DVMRP unicast routing.

ip dvmrp unicast-routing

- Use to enable the exchange of DVMRP unicast routes on an interface not owned by DVMRP.
- Example
  host1:boston(config-if)#ip dvmrp unicast-routing
- Use the no version to disable the exchange of DVMRP unicast routes on an interface not owned by DVMRP.
- See ip dvmrp unicast-routing.