What is BGP community additive?
A BGP community is bit of “extra information” that you can add to one of more prefixes which is advertised to BGP neighbors. This extra information can be used for things like traffic engineering or dynamic routing policies.
How do I check my community in BGP?
To show BGP routes which has specific BGP communities attribute, show ip bgp command can be used. The community value and community list can be used for show ip bgp command. show ip bgp community displays BGP routes which has communities attribute.
What is a BGP community string?
BGP can include more information with each prefix, in the form of Community Strings. A community string is a number value that the peer uses like a tag. Communities create routing policies between peers. By tagging prefixes with communities, we tell the peer to handle the prefixes in a special way.
How BGP communities are used?
BGP communities (as defined in RFC 1997) are used to signal reachability information between Autonomous Systems (ASes). In principle, BGP is used to distribute routes amongst peers, but for network-managing purposes it is possible to attach additional properties to each routing update.
How many community tags can be attached to a single BGP route?
32 communities
Any BGP prefix can have more than one tag (BGP community); each tag means something or leads to specific unique action. (you can attach up to 32 communities to a single route).
What is the difference between BGP community and extended community?
An extended community is an 8-octet value and provides a larger range for grouping or categorizing communities. BGP extended community attributes are specified in RFC 4360. You define the extended community list using the ip extcommunity-list command.
What is BGP community list?
A BGP community list is used to create groups of communities to use in a match clause of a route map. A community list can be used to control which routes are accepted, preferred, distributed, or advertised, for example. You can also use a community list to set, append, or modify the communities of a route.
How do I set up a BGP community?
To configure router R1 to send prefix marked with community:
- R1# configure terminal. R1 (config)# ip bgp- community new-format.
- R2# configure terminal.
- R1# show bgp ipv4 unicast neighbors 80.50.0.2 | i Community.
- R2# show bgp ipv4 unicast 94.70.40.0/24.
- R2# configure terminal.
- R2# show bgp ipv4 unicast 94.70.40.0/24.