Re: Best way to have redundancy announcing on separate routers

[Sam Roche <sroche () lakelandnetworks com>]

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

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________________________________
From: NANOG <nanog-bounces+sroche=lakelandnetworks.com () nanog org> on behalf of Jean Franco <jfranco () maila inf br>
Sent: Friday, December 27, 2024 6:09 PM
To: Tom Beecher <beecher () beecher cc>
Cc: Bryan Fields <Bryan () 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 <beecher () beecher cc<mailto:beecher () 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 <jfranco () maila inf br<mailto:jfranco () 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 <Bryan () bryanfields net<mailto:Bryan () 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