Concept Guide

• Enable the local router to support graceful restart as a receiver only.
CONFIG-ROUTER-BGP mode
bgp graceful-restart [role receiver-only]
Example conguration for enabling graceful restart
DellEMC# configure terminal
DellEMC(conf)# router bgp 400
DellEMC(conf-router_bgp)# bgp graceful-restart
DellEMC(conf-router_bgp)# exit
The above example conguration shows how to enable the BGP graceful restart. If you enter this command after the BGP session is
established, you must restart the session for the BGP graceful restart capability to be exchanged with the BGP neighbor.
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 aect 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 lter are dropped.
To congure an AS-PATH ACL to lter a specic 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 ltering.
CONFIG-AS-PATH mode
{deny | permit} filter parameter
This is the lter 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 lters 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 congured AS-PATH ACL for route ltering and manipulation.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} filter-list as-path-name {in | out}
If you assign an non-existent or empty AS-PATH ACL, the software allows all routes.
Border Gateway Protocol (BGP)
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