What are the BGP communities?
BGP communities are an optional transitive BGP attribute that can traverse from autonomous system to autonomous system. A BGP community is a 32-bit number that can be included with a route.
What are BGP communities used for?
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.
What are BGP community tags?
A BGP community is an optional, transitive BGP attribute that is recognized and passed to other BGP peers. You might see a BGP community as a tag attached to the BGP routes exchanged between two BGP peers.
What is the difference between community and extended communities in BGP?
The regular community attribute is four octets. An extended community is an 8-octet value that is also divided into two main sections. The first 2 octets of the community encode a type field while the last 6 octets carry a unique set of data in a format defined by the type field.
What are the different types of BGP communities?
Here are the 4 well known BGP communities: 1 Internet: advertise the prefix to all BGP neighbors. 2 No-Advertise: don’t advertise the prefix to any BGP neighbors. 3 No-Export: don’t advertise the prefix to any eBGP neighbors. 4 Local-AS: don’t advertise the prefix outside of the sub-AS (this one is used for BGP confederations ). More
Is the BGP community a 32 bit attribute?
BGP communities are an optional transitive BGP attribute that can traverse from autonomous system to autonomous system. A BGP community is a 32-bit number that can be included with a route.
How do I set a community to 100 in BGP?
Route-maps match the prefix lists, then set the community on the route. Group1 is assigned community 100, and Group2 is assigned community 200. By default, the communities are one large number, which is hard to read. The ip bgp-community new-format command changes this value to the ASN:Community format.
How are extended communities used in BGP routing?
This information identifies community members and enables you to perform actions on a group without having to elaborate upon each member. You can use community and extended communities attributes to trigger routing decisions, such as acceptance, rejection, preference, or redistribution.
