Switch 7700 Configuration Guide, v2

126 CHAPTER 5: ROUTING PROTOCOL OPERATION
By default, the MED metric is 0.
Comparing the MED Routing Metrics from the Peers in Different ASs
This comparison is used to select the best route. The route with smaller MED value
will be selected.
Perform the following configurations in BGP view.
By default, MED comparison is not allowed among the routes from the neighbors
in different ASs.
It is not recommended to use this configuration unless you can make sure that the
ASs adopt the same IGP and routing method.
Configuring a BGP Community
Community attributes are optional and transitive. Some community attributes are
globally recognized, which are called standard community attributes, whereas
some are for special purposes which are called extended community attributes.
You may define not only the standard community but also the extended
community attributes.
Community-list is used to identify a community, which falls into standard
community-list and extended community-list.
In addition, a route can have more than one community attributes. In a route, the
speaker of multiple community attributes can act according to one, several or all
the attributes. Router can choose to change the community attribute or leave it
unchanged before transmitting the route to its peers.
Perform the following configurations in system view.
By default, no BGP community is configured.
Tab le 106 Comparing the MED Routing Metrics from the Peers in Different ASs
Operation Command
Comparing the MED Routing Metrics from the
Peers in Different ASs
compare-different-as-med
Configure not to compare the MED routing
metrics from the peers in different ASs
undo compare-different-as-med
Tab le 107 Configuring a BGP Community
Operation Command
Configure a standard community list ip community-list standard-community-list-number {
permit | deny } { aa:nn | internet |
no-export-subconfed | no-advertise | no-export }
Configure an extended community list ip community-list extended-community-list-number {
permit | deny } as-regular-expression
Remove the configured community list undo ip community-list {
standard-community-list-number |
extended-community-list-number }