Good morning everyone!
We are setup to do eBGP peering with our one ISP currently. Not exchanging full routing tables but we receive 0.0.0.0/0 from ISP and we advertise our public /24 block that we own back to them.
We are getting a secondary provider brought in and are going to do eBGP peering with them as well. I have never done this ISP facing with eBGP but is it as straight forward as build a route-map-out to do as-path prepending outbound (prepending the AS 3 times seems to be the "normal" approach) so when both connections are up ISP2 does not think it should prefer our /24 block over ISP1? Then do a route-map inbound and set local-pref to 50 on secondary ISP so that way our FW prefers the primary connection over the secondary?
Im assuming I cannot really use SD-WAN SLAs and rules to failover traffic since if the link goes out of SLA but doesn't actually drop the BGP neighborship with ISP1 and I start sending traffic out ISP2 I will have asymmetric routing.
All my experience in the past has been with 2 different ISPs and 2 different IP blocks and just using Route53 to failover inbound traffic by changing DNS entries and failing over outbound with SLAs and SD-WAN.
Thanks for the input!
Source: r/fortinet · by /u/FailSafe218