>suaveguru wrote:
>>
>> knows anything below what it does ?
>>
>> route-map MikeTest permit 10
>> set community 6461:701 additive
>
>Adds community 6461:701 to the list of communities
>carried with the route. Without keyword 'additive',
>it will remove other communities.
>
>It is used with BGP.
>
>Saöa
Excellent explanation of what the command itself does. One of the
hard things in learning real world "BGP" is that the Border Gateway
Protocol (BGP) is a small part of the complexity of global internet
routing.
In this example, the meaning of community 6461:701 is defined by AS
6461 (the part before the :). While this community will be used to
make some sort of policy decision, the actual policy, contrary to
many discussions, is NOT carried by BGP. For example, community 701
of AS 6461 might mean that an AS _should_ treat routes with this
community as high precedence. A receiving AS is not obligated to do
so, and, unless there are prior agreements with AS 6461, may not even
know that is the intended meaning.
To take a different example, let's say AS 6461 is an academic
research network manager. Other universities belonging to the same
network will recognize community 701 routes as belonging to the
research network. Indeed, if another university were AS 6060, it
still might originate routes with origin AS 6060 but community
6461:701, because all the participants know that 6461:701 denotes
membership in the cooperative network.
The meaning of communities MAY be available from routing registries,
but may simply be a private admininistrative agreement between AS.
The key things to remember:
Policies are implemented in filters/route list match/set, etc.
statements that are not transmitted by BGP
Information to make policy decisions is transmitted by BGP.
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