If a given router does not understand or use the community attribute, the
route is not dropped and the community is passed along in updates sent to
other BGP neighbors. The statement you originally posted simply says this:
Any given router need not use the community attribute, but that information
must remain intact so that other routers might make use of it should they
decide to do so.
A BGP community is strictly an administrative attribute. It has zero effect
on routing if your router is not configured to use that information.
However, your router needs to forward that information intact to other
neighbors in case they need it to enforce whatever routing or filtering
policies they have implemented.
HTH,
John
> I could understand this since this is a transitive attribute and
therefore it can
> transit the routers and can be passed.
> But there is a condition imposed by whereby it says that the remote
router maynot
> understand the community but it shall be configured to propogate it to
the next hop
> destination or transit router else by default the communities are
dropped. Now if the
> communities are dropped "does this mean that the route is dropped" since
the coomunity
> attribute is resposible for the routes .......
>
> Thanks
> Manish
>
> John Neiberger wrote:
>
> > Here's a guess. The BGP community attribute is optional, yet
transitive.
> > This means that a particular implementation of BGP on a router may not
use
> > or understand the concept of communities. However, because the
attribute is
> > transitive, it will be forwarded along to other neighbors who may be
able to
> > to use it.
> >
> > I'm sure someone will correct me if I have the wrong.
> >
> > Regards,
> > John
> >
> > > What does this mean :
> > >
> > > "IF A ROUTER DOESNOT UNDERSTAND THE CONCEPT OF COMMUNITIES IT WILL
DEFER
> > TO THE NEXT ROUTER"
> > >
> > > Please help.
> > > Thanks
> > > Manish
> > >
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