Dell S4048T, Configuration Manual

Page: 241 / 1277

• Local router supports graceful restart for this neighbor or peer-group as a receiver only.
CONFIG-ROUTER-BGP mode
neighbor { ip-address | peer-group-name } graceful-restart [role receiver-only]
• Set the maximum time to retain the restarting neighbor’s or peer-group’s stale paths.
CONFIG-ROUTER-BGP mode
neighbor { ip-address | peer-group-name } graceful-restart [stale-path-time time-
in-seconds ]
The default is 360 seconds .
Filtering on an AS-Path Attribute
You can use the BGP attribute, AS_PATH, to manipulate routing policies.
The AS_PATH attribute contains a sequence of AS numbers representing the route’s path. As the route
traverses an AS, the ASN is prepended to the route. You can manipulate routes based on their AS_PATH to
affect interdomain routing. By identifying certain ASN in the AS_PATH, you can permit or deny routes based
on the number in its AS_PATH.
AS-PATH ACLs use regular expressions to search AS_PATH values. AS-PATH ACLs have an “implicit deny.”
This means that routes that do not meet a deny or match filter are dropped.
To configure an AS-PATH ACL to filter a specific AS_PATH value, use these commands in the following
sequence.
1 Assign a name to a AS-PATH ACL and enter AS-PATH ACL mode.
CONFIGURATION mode
ip as-path access-list as-path-name
2 Enter the parameter to match BGP AS-PATH for filtering.
CONFIG-AS-PATH mode
{deny | permit} filter parameter
This is the filter that is used to match the AS-path. The entries can be any format, letters, numbers, or
regular expressions.
You can enter this command multiple times if multiple filters are desired.
For accepted expressions, refer to Regular Expressions as Filters .
3 Return to CONFIGURATION mode.
AS-PATH ACL mode
exit
4 Enter ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
5 Use a configured AS-PATH ACL for route filtering and manipulation.
Border Gateway Protocol IPv4 (BGPv4) 241