Simple BGP with two operators, one advertisement and prepending

[Wojciech Bajorek]

Hi,

It seems that rp_filter was the key. Both BGP sessions are up, thanks for
tip.

Now, I have a different topic - can you suggest a solution to overcome
situation, where one ISP sends two AS numbers and in most cases their path
is longer for outgoing traffic?

Regards,
Wojciech Bajorek


2017-04-25 15:46 GMT+02:00 Wojciech Bajorek <wojciech.bajorek at gmail.com>:

> Thanks, you might be right, indeed rp_filter was enabled.
>
> I will test it today and see if it helps.
>
> Does it mean that my config is just fine?
>
> Regards,
> Wojciech Bajorek
>
>
> 2017-04-25 12:36 GMT+02:00 Andrew <nitr0 at seti.kr.ua>:
>
>> 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 then
>>         {
>>                 accept;
>>         }
>>         else reject;
>> }
>>
>> filter bgp_isp2_out {
>>         if net = 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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