We have a similiar setup with each of our BGP routers connected to different ISPs. Each ISP sends us full tables.
The simplest method we came up with for outbound connection redundancy was to have router 1 use a default route to router 2, and router 2 use a default route to router 1. We don't redistribute those static defaults or our learned BGP routes to the other routers. During normal times, that default route is never used, as there are more specific routes learned via BGP. If router 1 loses its connection to ISP 1 for any reason, it simply pushes traffic over to router 2 as it's routing table only has the default and any learned OSPF routes from our PE boxes. Outbound traffic from router 1 then goes out through my BGP router 2, then ISP2 based on its learned BGP routes. Redundancy for inbound traffic just works via BGP magic 🙂. 10+ years with this setup and no major issues that we know of. We do have more config & peers on the routers, but I've omitted that for simplicity. ISP 1(announcing full tables) <---> <my BGP router01> ============<my BGP router02> <------>ISP2 (announcing full tables) Happy New Year everyone!! Sam Roche Manager, Network Operations [Logo Description automatically generated] 196 Taylor Road, Bracebridge, ON P1L 1J9 Support: supp...@lakelandnetworks.com<mailto:supp...@lakelandnetworks.com> 705-640-0556 TF: 1-844-444-4249 Direct: sro...@lakelandnetworks.com<mailto:sro...@lakelandnetworks.com> 705-640-0086 | https://www.lakelandnetworks.com/faqs/ Lakeland Networks<http://www.lakelandnetworks.com/> ________________________________ From: NANOG <nanog-bounces+sroche=lakelandnetworks....@nanog.org> on behalf of Jean Franco <jfra...@maila.inf.br> Sent: Friday, December 27, 2024 6:09 PM To: Tom Beecher <beec...@beecher.cc> Cc: Bryan Fields <br...@bryanfields.net>; nanog@nanog.org <nanog@nanog.org> Subject: Re: Best way to have redundancy announcing on separate routers Hi Tom, This is exactly what I was planning. I'm announcing a block via ISP1 and another set of blocks via ISP2, and have iBGP running between them. Thanks a lot!! Best regards, On Fri, Dec 27, 2024 at 1:00 PM Tom Beecher <beec...@beecher.cc<mailto:beec...@beecher.cc>> wrote: Jean- Yeah, don't worry about people complaining. Is this an accurate description of what you are trying to achieve? - Have 2 different sets of prefixes that you announce. Set A via router1/ISP1 , Set B via router2/ISP2 - If BGP to one of your ISPs goes down, start announcing those prefixes to the other ISP. ( Example, if ISP2 goes down, start announcing prefix Set B over ISP1 ) On Thu, Dec 26, 2024 at 8:16 AM Jean Franco <jfra...@maila.inf.br<mailto:jfra...@maila.inf.br>> wrote: Hi guys, I've been on the list for as long as I cannot even remember. So just you know, I'm not new at this. This is no easy task, that's why I came here looking for help. I'm sorry if I brought anguish to the experts on the list! I thought I could bring something that someone may have experienced before. I haven't solved this yet, but at least I've received some valuable suggestions and I Thank you! About all the details of the connections, numbers of peerings, PNI's and IXP's I have left them out, since I figured this additional information could make things worse. ISP 1 <router01> ====20KM====<Router>====20KM====<router02> ISP2 The ISP connections are all 10G. I don't believe these routers are DFZ capable. All the routers are well capable and already receive the full routes. The connections between these routers are 40G. Best regards, On Thu, Dec 26, 2024 at 12:53 AM Bryan Fields <br...@bryanfields.net<mailto:br...@bryanfields.net>> wrote: On 12/25/24 6:18 PM, Randy Bush wrote: > where does one go for is-is help? the mtu issie can be painful!!! I think here would be good too. I recently had to do this between a Cisco 3945e and a Juniper, and from my unrevised notes: vlan { unit 405 { family iso { # holy shit this is important. CISCO and Juniper will not talk unless the MTU is set mtu 1492; } } } :-) -- Bryan Fields 727-409-1194 - Voice http://bryanfields.net
