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454 CHAPTER 30: CONFIGURING BGP
By default, the route from the peer or peer group is not designated with any route
policy.
10 Create an filtering policy based on access list for the peer.
Table 520 Create a Fltering Policy Based on Access List for the Peer
By default, no route filtering policy based on IP ACL for a peer is set.
11 Create BGP route filtering based on the AS path for the peer. By default, a BGP
filter is disabled.
Table 521 Create a BGP Route Filtering Based on AS Path for the Peer
Setting the MED for the
AS
The multi-exit discriminator (MED) is the external metric of a route. It is different
from the local preference attribute. MED is switched between ASs and the MED
that has entered the AS does not leave the AS. AS uses local attributes for its own
out-site selection processing while MED attribute is used to select the best route.
The route with smallest MED value is selected. When a router running BGP gets
routes with the same destination address but a different next hop through
different external peers, it makes a preference selection based on the MED values.
To operate the MED attribute, an access control list is used to indicate what
network will be operated.
Perform the following configurations in BGP view.
Table 522 Configure the BGP MED Metric
Allow Comparing Path
MED
This command is used to compare MED values from different AS neighboring
routes and to select the best route. The route with smaller MED value is selected.
Perform the following configurations in BGP view.
Table 523 Allow Comparing Path MED
Operation Command
Create an filter policy based on access list
for the peer
peer peer-address filter-policy
acl-number { import | export }
Remove an filter policy based on the
access list for the peer
undo peer peer-address filter-policy
acl-number { import | export }
Operation Command
Create a BGP route filtering based on AS
path for the peer
peer peer-address acl
aspath-list-number { import | export
}
Delete a BGP route filtering based on AS
path for the peer
undo peer peer-address acl
aspath-list-number { import | export
}
Operation Command
Configure MED for an AS default-med med
Restore the default MED of an AS undo default-med
Operation Command