Concept Guide

○ confed: Chooses the bestpath MED comparison of paths learned from BGP confederations.
○ missing-as-best: Treats a path without a MED value as the most preferred one.
To view the non-default values, use the show config command in CONFIGURATION ROUTER BGP mode.
Manipulating the COMMUNITY Attribute
A COMMUNITY attribute indicates that all the routes with that attribute belong to the same community grouping. In addition to
permitting or denying routes based on the values of the COMMUNITY attributes, you can manipulate the COMMUNITY attribute
value and send the COMMUNITY attribute with the route information.
By default, Dell EMC Networking OS does not send the COMMUNITY attribute to a BGP neighbor or a peer group.
To send the COMMUNITY attribute to BGP neighbors, use the following command.
● Enable the software to send the router’s COMMUNITY attribute to the BGP neighbor or peer group specified.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} send-community [extended |
standard]
extended- Allows to send the extended community attribute to a BGP neighbor or peer group.
standard- Allows to send the standard community attribute to a BGP neighbor or peer group.
To view the BGP configuration, use the show config command in CONFIGURATION ROUTER BGP mode.
If you want to remove or add a specific COMMUNITY number from a BGP path, you must create a route map with one or both
of the following statements in the route map. Then apply that route map to a BGP neighbor or peer group.
1. Enter ROUTE-MAP mode and assign a name to a route map.
CONFIGURATION mode
route-map map-name [permit | deny] [sequence-number]
2. Configure a set filter to delete all COMMUNITY numbers in the IP community list.
CONFIG-ROUTE-MAP mode
set comm-list community-list-name delete
OR
set community {community-number | local-as | no-advertise | no-export | none}
Configure a community list by denying or permitting specific community numbers or types of community.
● community-number: use AA:NN format where AA is the AS number (2 or 4 Bytes) and NN is a value specific to that
autonomous system.
● local-AS: routes with the COMMUNITY attribute of NO_EXPORT_SUBCONFED and are not sent to EBGP peers.
● no-advertise: routes with the COMMUNITY attribute of NO_ADVERTISE and are not advertised.
● no-export: routes with the COMMUNITY attribute of NO_EXPORT.
● none: remove the COMMUNITY attribute.
● additive: add the communities to already existing communities.
3. Return to CONFIGURATION mode.
CONFIG-ROUTE-MAP mode
exit
4. Enter the ROUTER BGP mode.
CONFIGURATION mode
router bgp as-number
5. Apply the route map to the neighbor or peer group’s incoming or outgoing routes.
CONFIG-ROUTER-BGP mode
neighbor {ip-address | ipv6-address | peer-group-name} route-map map-name {in | out}
To view the BGP configuration, use the show config command in CONFIGURATION ROUTER BGP mode. To view a route
map configuration, use the show route-map command in EXEC Privilege mode.
Border Gateway Protocol (BGP)
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