Extended Community Attributes
The extended community attribute provides a mechanism to label
BGP (Border Gateway Protocol) routes. It provides two important enhancements over
the standard community attribute:
- An expanded range. Extended communities are 8-bytes wide,
whereas regular communities were only 4-bytes wide. So, this ensures that
extended communities can be assigned for a plethora of uses, without the fear of
overlap.
- The addition of a 'Type' field provides structure for the
extended community
The following two types of extended communities are available:
- Route Target (RT)
- Site Of Origin (SOO)
Although these two community types are generally used in L3 VPN
network setup, you can also use them in a non-L3 VPN network to
control the distribution of BGP routes.
BGP does not send either the extended or standard community attributes to
their neighbors by default; you must use the configuration command configure bgp
neighbor send-community.
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