Known communities for AS174?
Adam Rothschild
asr+nanog at latency.net
Tue Mar 22 19:52:20 UTC 2005
On 2005-03-22-03:30:32, David Hubbard <dhubbard at dino.hostasaurus.com> wrote:
[...]
> 3. Communities controlling Cogents AS path prepending
> for customer routes on egress:
>
> community effect
> 174:3000 do not announce
> 174:3001 prepend 174 1 time
> 174:3002 prepend 174 2 times
> 174:3003 prepend 174 3 times
>
> But I've tried setting each of those and it doesn't
> seem to have any effect. Anyone know if that info is
> out of date or maybe has something else to try?
I'm of the understanding that Cogent supports the following BGP
communities (and no others):
174:990 - This community makes sure that the customer's route
does not leave the Cogent AS of 16631. What this
means is that if a peering partner or BGP customer
of Cogent is trying to send traffic to this route,
the peering partner or BGP customer of Cogent will
not see this route from Cogent, and will therefore
not send packets for that destination to the Cogent
network.
174:991 - This community makes sure that the customer's routes
are not passed on to Cogent's peering or transit
partners, but are sent to Cogent's BGP
customers. Almost the same situation as 16631:990,
except that BGP customers of Cogent will see the
route, and will have the option of sending those
packets via Cogent.
174:10,95,100,105,110 - Each of these communities sets a
different local preference on a
customer's routes. A detailed
explanation of what these are is
beyond the scope of this
document. However, 16631:10 will have
the effect that even inside the Cogent
network, the Cogent network will
prefer any other path seen as best
before using the customer's line. This
could be used, for example, if a
customer has a line with another ISP,
and wants to never use the Cogent line
for traffic (even from Cogent itself)
except when the other line is down.
With that said, your best bet might be to contact support at cogentco.com
and request an updated list.
Hope this helps,
-a
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