12-18-2015 02:38 AM - edited 03-05-2019 02:57 AM
Hi Everyone,
Is it possible and advisable to advertised/received default routes and full routes on a multi-homed bgp setup?
Thanks
12-18-2015 06:19 AM
Hello,
It is completely depending on what you are going to do.
Advertising Full BGP routes is not suggested if you are an end customer. it may cause your AS become a transit AS. Costumers usually only advertises their own IP addresses to avoid that.
If you are going to implement full load balancing across both links, you need to receive full BGP routes. However, receiving full BGP routes is very intensive in terms of memory and processing. It will be also very complex so troubleshooting is difficult.
Some ISPs gives you an option to receive a default route and partial routes. You can consider one of your link as a primary link and other as backup. Then you can send traffic of partial routes through your backup link and other traffic through your primary link by implementing policy.
Load balancing is not going to be even but your primary link probably would have higher bandwidth than your backup.
Hope it helps,
Masoud
12-18-2015 07:05 AM
Yep, I agree with Masoud it will be Load Sharing.
** Do Not Advertise Full Routing Table **, Just advertise your Public Routes and make sure to put an ACL on your public Interface.
If you are going to implement full load balancing across both links, you need to receive full BGP routes. However, receiving full BGP routes is very intensive in terms of memory and processing. It will be also very complex so troubleshooting is difficult. --> Check your IPOP Hardware/Router's Capacity.
You might end up doing asymmetric routing too, I will suggest use primary and back up, unless you are highly skilled.
Regards,
Saurabh Gera
12-18-2015 07:36 AM
Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
Yes it's possible, advisable is debatable.
When you take full routes, you're routers than have the option of using the "best" path to any destination, but as BGP (by default) only considers the better path as having the fewest ASs to cross, the "best" path might not actually be the "best" path.
As Masoud also notes, you can take (or just only accept) partial routes. For example, you might use a default and take prefixes that only come from your ISP AS or just one AS hop from it.
If your routers support PfR, it can select the actual best performing path, and it can work with just using defaults to using full Internet tables. I found PfR works very well with defaults.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide