What is extended community in BGP?
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. Extended communities provide a larger range for grouping or categorizing communities.
What are three extended BGP communities?
The values are:
- 0x00 (RFC 4360) – 2-octet AS Specific Extended Community. Global Administrator – 2 octets representing the 2-byte AS number.
- 0x01 (RFC 4360) – IPv4 Address Specific Extended Community.
- 0x02 (RFC 5668) – 4-octet AS Specific BGP Extended Community.
- 0x03 (RFC 4360) – Opaque Extended Community.
What is extended community in BGP in Cisco?
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 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.
What is RT and RD in BGP?
The Route-Distinguisher (RD) & Route-Target (RT) are two different concepts that are both used in an MPLS VPN. The RD is used to keep all prefixes in the BGP table unique, and the RT is used to transfer routes between VRF’s/VPNS. So the answer is; by using a route-target.
How do I check my BGP community?
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.
How many BGP communities are there?
There are 4 well known BGP communities that you can use or you can pick a numeric value that you can use for your own policies.
How is BGP extended community attached to route?
The extended community is attached to a BGP route the same way standard BGP communities or any other BGP attributes are. The MP-iBGP update propagates the extended community along with other BGP attributes between PE-routers, and its value determines to which VRF or set of VRFs to import the route.
How many octets are in BGP extended community attribute?
Each of the extended community attributes has a defined community type code of 16 and is encoded as an 8-octet value. The first two octets define the attribute type, and the next six octets hold the value of the attribute.
Is there BGP support for named extended community lists?
The BGP Support for Named Extended Community Lists feature introduces the ability to configure extended community lists using names in addition to the existing numbered format. Feature History for the BGP Support for Named Extended Community Lists feature
When to use BGP with Soo extended community?
SOO also is used only if BGP is used to achieve the PE to CE connectivity. Figure 9-6 illustrates this concept, and shows a site connected to two separate PE-routers and the behavior of the PE-router when a route is received that contains a SOO extended community that matches the one configured for the VRF.