Exam 400-007 topic 1 question 256 discussion

There's some assumptions and deductions to be made. I would Peer the firewalls together so they both see the same thing from a BGP perspective and from Site-X, I would advertise a longer match, this would solve the asymmetric routing being seen.

I thought C was the right answer with longer prefix as the solution to resolve the asymmetric routing. However, by doing so the symptom would be shifted to Site-Y. The permanent solution is to have Site-X and Site-Y using unique IP Pools.

C, longer prefix

WTF. It's Internet connection. Supposedly to ISP. MED is not transitive attribute. As you know, we are using AS-Path/communities to make that stuff. All answers are literally wrong.

Use BGP MED to influence Site-X return traffic: By assigning a lower MED (Metric) to the Site-X route, BGP will prefer using the Site-X link for return traffic, thus resolving the issue of traffic going back through Site-Y. Change the IP address scheme of both sites: This is a more permanent solution but involves more significant changes. Assigning different IP address ranges to each site ensures that return traffic is directed to the correct site without relying on BGP MED. Using BGP MED is the most efficient and effective way to correct the traffic routing in this scenario.

there is no mention of a firewall in the question

they need to split the IP addressing between site x and y.

B might be the right answer. Replicating the firewall policy on both sites is a good practice should the primary site x fail. Also advertising low MED can influence return traffic. My worry is that MED is a non transitive attribute and also there is nothing said about MED config on site y. - no static route needed towards the internet on site x, we know the traffic leave correctly - longer prefix match won't help at it won't be installed in the routing table when comparing it to the shorter prefix - no need change the IP address schema, that might require many other updates: update firewall policies, prefix lists/route maps, wide ips, etc.