Configuring bgp route attributes, Configuration prerequisites, Specifying a preferred value for routes received – H3C Technologies H3C SR8800 User Manual
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Step Command
Remarks
3.
Configure a shortcut route.
network ip-address [ mask | mask-length ]
short-cut
Optional.
By default, an EBGP
route received has a
priority of 255.
Configuring BGP route attributes
Configuration prerequisites
Create BGP connections.
CAUTION:
•
Using a routing policy can set preferences for routes matching it. Routes not matching it use the default
preferences.
•
If other conditions are identical, the route with the smallest MED value is selected as the best external
route.
•
Using the peer next-hop-local command can specify the router as the next hop for routes to a
peer/peer group. If BGP load balancing is configured, the router specify itself as the next hop for routes
to a peer/peer group regardless of whether the peer next-hop-local command is configured.
•
In a “third party next hop" network—the two EBGP peers reside in a common broadcast subnet, the
BGP router does not specify itself as the next hop for routes to the EBGP peer, unless the peer
next-hop-local command is configured.
•
In general, BGP checks whether the AS_PATH attribute of a route from a peer contains the local AS
number. If so, it discards the route to avoid routing loops.
•
You can specify a fake AS number to hide the real one as needed. The fake AS number applies to routes
to EBGP peers only, that is, EBGP peers in other ASs can only find the fake AS number.
•
The peer substitute-as command is used only in specific networking environments. Inappropriate use of
the command may cause routing loops.
•
If you both reference a routing policy and use the peer {
group-name | ip-address } preferred-value
value command to set a preferred value for routes from a peer/peer group, the routing policy sets the
specified preferred value for routes matching it. Other routes not matching the routing policy uses the
value set with the peer {
group-name | ip-address } preferred-value value command. If the preferred
value specified in the routing policy is zero, the routes matching it will also use the value set with the peer
{
group-name | ip-address } preferred-value value command. For how to use a routing policy to set a
preferred value, see the command peer {
group-name | ip-address } route-policy route-policy-name
{ export | import } command and the apply preferred-value
preferred-value command.
Specifying a preferred value for routes received
By default, routes received from a peer have a preferred value of 0. Among multiple routes that have the
same destination/mask and are learned from different peers, the one with the greatest preferred value
is selected as the route to the destination.
To specify a preferred value for routes from a peer or peer group: