Good morning,
I recently became AS (Autonomus System).
As from the beginning I have configured an eBGP Router that announces my Public / 29 network.
All this through a single ISP.
Now I find myself needing to set up a second backup ISP.
Both allow me to get the FIRT (Full Internet Routing Table) but I have no idea how to set up a backup eBGP session in case my primary ISP is down.
Do you have any sample configurations or you could direct me to some useful guides.
Thanks a lot in advance.
Hi, just set up the eBGP session with the second Upstream. If both providers send you the Full Table, the router will select the best path based on the internal algorithm that takes into account various parameters (AS-PATH, local-pref etc.)
With a standard configuration, outgoing traffic will then go to the ISP with the best route. You can still force the behavior of outbound traffic through routing filters.
If ISP1 drops the FIRT will be withdrawn within a few seconds so the outgoing traffic will go to ISP2.
Inbound traffic will follow the same logic, if ISP1 goes down you will withdraw your ads on it
You can prefer inbound traffic to an ISP via routing filters (Set BGP-Prepend, for example)
Is this a /29 of IPv6 or IPv4?
Is your ASN a private one for routing between you and the ISP or are you intending to announce into the global routing table? If the later, it will only work with a minimum of /24 of IPv4 or /48 of IPv6. Any smaller then this and a large percentage of the internet (including us) will filter your routes out.
EBGP is intended to be always on - not active / fail over.
You are advised to get full tables to obtain the most benefit from diverse uplines. Make sure your router can handle this - ie: CCR1009 or better. The CCR2004 is a good choice.
Unless you have a specific reason for preferring one ISP I would treat them both equally and let the traffic fall where it may. Do be aware you can really only control your ongoing traffic. You could try and engineer incoming through AS-prepend but this only has limited effect. Also be aware no matter what you do - upline ISP’s and their uplines will always prefer to send you the traffic through a client of theirs (local pref) regardless of anything else.