Simple BGP with two operators, one advertisement and prepending

[Andrew]

Maybe you forgot to disable rp_filter on uplink ifaces?

And prepend works for incoming traffic, for outgoing - there is 
localpref. So, if outgoing traffic goes via ISP2 and incoming passed via 
ISP1 - it's dropped if rp_filter is enabled.

On 25.04.2017 10:36, Wojciech Bajorek wrote:
> Hi,
>
> I have a pretty simple BGP configuration with two ISP and one static 
> subnet to advertise.
> There is also one prepending configured but I'm not sure if it's working.
>
> The thing is that for some reason when I connect both ISP peers, 
> traffic to the advertised ISP#2 networks (with shorter path) stops 
> working after a couple of seconds. Tracert shows the last hop as ISP#2 
> border router.
>
> Similar configuration on Juniper router works without any problem, so 
> I'm afraid that there is an error within my Bird config.
> Can you please help me out?
>
> PS. Without prepending situation is exactly the same.
>
> OS: Debian 8
> Bird: 1.4.5-1+deb8u1
>
> router id 90.90.90.1;
>
> protocol kernel {
>         persist;
>         scan time 15;
>         import all;
>         export all;
> }
>
> protocol device {
>         scan time 10;
> }
>
> filter bgp_isp1_out {
>         if net = 90.90.90.0/24 <http://90.90.90.0/24> then
>         {
>                 accept;
>         }
>         else reject;
> }
>
> filter bgp_isp2_out {
>         if net = 90.90.90.0/24 <http://90.90.90.0/24> then
>         {
>                 bgp_path.prepend(12345);
>                 bgp_path.prepend(12345);
>                 accept;
>         }
>         else reject;
> }
>
> protocol bgp bgp_isp1 {
>         import all;
>         export filter bgp_isp1_out;
>
>         local as 12345;
>         neighbor 2.3.4.5 as 2345;
> }
>
> protocol bgp bgp_isp2 {
>         import all;
>         export filter bgp_isp2_out;
>
>         local as 12345;
>         neighbor 3.4.5.6 as 3456;
> }
>
>
> Thank you.
>
> Regards,
> Wojciech Bajorek


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