I'm building the CDN for Zattoo and as it's some sort of 'anycast' infrastructure (refer to the presentation @ SwiNOG #14), I have several geographically dispersed network islands, not connected via a layer-2 link.
Each network island propagates one or more /24 networks, using AS8302.
Now, BGP mechanism prevents AS-pathes like
^[Transit-AS]_8302$
in my case
^13030_8302$
if I'm AS8302 myself.
I know there is some tweak to prevent this default behaviour. Could anyone give a hint for Foundry and Cisco gear?
Thanks, Fredy
Hi Fredy,
On Thu, 7 Jun 2007, Fredy Kuenzler wrote:
I'm building the CDN for Zattoo and as it's some sort of 'anycast' infrastructure (refer to the presentation @ SwiNOG #14), I have several geographically dispersed network islands, not connected via a layer-2 link.
Each network island propagates one or more /24 networks, using AS8302.
Now, BGP mechanism prevents AS-pathes like
^[Transit-AS]_8302$
in my case
^13030_8302$
if I'm AS8302 myself.
I know there is some tweak to prevent this default behaviour. Could anyone give a hint for Foundry and Cisco gear?
you may want to use the "allowas-in" statement in the neighbor configuration (at least on cisco)
allowas-in Accept as-path with my AS present in it
-> neighbor 1.2.3.4 allowas-in
Kind regards, Michael
Fredy Kuenzler wrote:
I'm building the CDN for Zattoo and as it's some sort of 'anycast' infrastructure (refer to the presentation @ SwiNOG #14), I have several geographically dispersed network islands, not connected via a layer-2 link.
Each network island propagates one or more /24 networks, using AS8302.
Now, BGP mechanism prevents AS-pathes like
^[Transit-AS]_8302$
in my case
^13030_8302$
if I'm AS8302 myself.
I know there is some tweak to prevent this default behaviour. Could anyone give a hint for Foundry and Cisco gear?
Normally BGP speakers MUST not be able to disable loop prevention. You're probably thinking of "no bgp enforce-first-as" but that's not relevant here. There was another hack related to network transitions and have two ASs configured at the same time. Though I don't know if this is good enough either.
As an alternative you can have a static route for your entire anycast netblock to one of your upstreams. That fixes the immediate issues but doesn't provide load balancing or failover.
Fredy Kuenzler wrote:
I'm building the CDN for Zattoo and as it's some sort of 'anycast' infrastructure (refer to the presentation @ SwiNOG #14), I have several geographically dispersed network islands, not connected via a layer-2 link.
Each network island propagates one or more /24 networks, using AS8302.
Now, BGP mechanism prevents AS-pathes like
^[Transit-AS]_8302$
in my case
^13030_8302$
if I'm AS8302 myself.
I know there is some tweak to prevent this default behaviour. Could anyone give a hint for Foundry and Cisco gear?
Ah, here it is. It may work with some tweaks.
http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chap... http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example0918...
Michael Horn schrieb:
Now, BGP mechanism prevents AS-pathes like
^[Transit-AS]_8302$
in my case
^13030_8302$
if I'm AS8302 myself.
I know there is some tweak to prevent this default behaviour. Could anyone give a hint for Foundry and Cisco gear?
you may want to use the "allowas-in" statement in the neighbor configuration (at least on cisco)
allowas-in Accept as-path with my AS present in it
-> neighbor 1.2.3.4 allowas-in
Thanks Michael and Ueli, who pointed me to the same command. This in fact fixes the issue, at least on Cisco.
No I have to find the similar command on Foundry.
Best regards, Fredy
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Andre Oppermann -
Fredy Kuenzler -
Michael Horn