on 03-23-2023 01:11 PM
This Nominated Discussion Article is based on the post "Palo Alto BGP routes from Azure" by @S_Williams901. Read on to see Cyber Elite @aleksandar.astardzhiev response!
Palo 5220 running at the edge, using VPN tunnel to Azure virtual WAN running eBGP. Palo iBGP peered to switches, switches peered eBGP to Azure Express Route. My issue is VPN route is always installed in route table rather than express route, I assume because eBGP is AD 20 vs iBGP AD 200. I have tried local pref and weight on the palo to try and force it to install iBGP route coming from Express route with no luck. Any one else have a similar issue?
During route lookup administrative distance is always first to check, so no matter what MED, local pref or weight you set eBGP will always be preferable. AD is used to select route learned from different routing protocols, while the BGP metrics will be used when multiple routes from same routing protocol were learned.
Obviously the quick and dirty fix is to increase (or decrease) administrative distance metric for either iBGP or eBGP. However you need to double check how this will effect any other routing in your environment, since this change is per virtual-router and will affect all routes
Have you considered the option to use eBGP between firewall and switches? You could assign dedicate private AS number to the firewall, which is different from the AS of the switches. This way you could play with BGP metrics and tell FW to use express route when available.