Hello, I'm looking for a way to do path prepending for my prefix as it leaves AS174 (Cogent), one of my upstreams. The following: http://www.radb.net/cgi-bin/radb/whois.cgi?obj=AS174 suggests that at least as recently as last May they might have accepted: 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 Anyone know if that info is out of date or maybe has something else to try? Thanks, David
dhubbard@dino.hostasaurus.com (David Hubbard) wrote:
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 Anyone know if that info is out of date or maybe has something else to try?
Are you sure you're sending communities? Elmar. -- "Begehe nur nicht den Fehler, Meinung durch Sachverstand zu substituieren." (PLemken, <bu6o7e$e6v0p$2@ID-31.news.uni-berlin.de>) --------------------------------------------------------------[ ELMI-RIPE ]---
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 Anyone know if that info is out of date or maybe has something else to try?
In addition to Elmar's comment, are you clearing the BGP session (either soft outbound or hard, soft recommended) so that your announced prefixes reflect the policy change? Stephen
On 2005-03-22-03:30:32, David Hubbard <dhubbard@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 Anyone know if that info is out of date or maybe has something else to try?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@cogentco.com and request an updated list. Hope this helps, -a
On Tue, Mar 22, 2005 at 02:52:20PM -0500, Adam Rothschild wrote:
On 2005-03-22-03:30:32, David Hubbard <dhubbard@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
I'm of the understanding that Cogent supports the following BGP communities (and no others):
[ snip ] Not a Cogent customer, but they have a list of supported communities in the comments for the RIPE RR entry for AS174 (which seems to have been updated fairly recently). The communities shown in the original post also show up there. w
participants (5)
-
Adam Rothschild -
David Hubbard -
Elmar K. Bins -
Stephen Stuart -
Will Yardley