Setting the MED Attribute for MBGP Routes

The MED attribute indicates the metric used in IGP. After the MED attribute is set for routes, an EBGP peer can select a route with the smallest MED value for the traffic that enters an AS.

Context

The MED serves as the metric used by an IGP. MED determines the optimal route when traffic enters an AS. When an MBGP router obtains multiple routes to the same destination address but with different next hops through EBGP peers, the route with the smallest MED value is selected as the optimal route.

Procedure

Set the default MED value on the local device.
1. Run system-view
  The system view is displayed.
2. Run bgp as-number
  The BGP view is displayed.
3. Run ipv4-family multicast
  The BGP-IPv4 multicast address family view is displayed.
4. Run default med med
  The default MED value is set.
5. Run commit
  The configuration is committed.
Enable MBGP to compare the MED values of the routes from different ASs.
1. Run system-view
  The system view is displayed.
2. Run bgp as-number
  The BGP view is displayed.
3. Run ipv4-family multicast
  The BGP-IPv4 multicast address family view is displayed.
4. Run compare-different-as-med
  The function to compare the MED values of routes from different ASs is enabled.
5. Run commit
  The configuration is committed.
Configure MBGP to use the maximum MED value for a route that has no MED value.
1. Run system-view
  The system view is displayed.
2. Run bgp as-number
  The BGP view is displayed.
3. Run ipv4-family multicast
  The BGP-IPv4 multicast address family view is displayed.
4. Run bestroute med-none-as-maximum
  The maximum MED value is used for a route if the route has no MED value.
  
  If this command is not configured, MBGP uses 0 as the MED value for a route if the route has no MED value.
5. Run commit
  The configuration is committed.