On 1/23/2020 6:01 PM, Brian wrote:
Hello all. I am having a hard time trying to articulate why a Dual Home ISP should have full tables. My understanding has always been that full tables when dual homed allow much more control. Especially in helping to prevent Async routes.
Brian, you're correct that having more routing information will give you more control over routing decisions. However, for me, it's not about control/traffic engineering but about basic redundancy/availability. Taking full tables gives you visibility into whether an actual path exists (or does not exist) via each of your upstream providers. If you just take a default route originated by your peer you'll only have visibility that there's a connection between your router and your peer - not to the rest of the internet or to a specific destination past your peer. As Job said, maintenance, router reboots, and other upstream connectivity issues can cause an upstream peer to be missing routes that the other peer might have. In my experience, most folks multi-home for improved redundancy/availability. So for those that are multi-homed, I recommend taking full tables so that you can get the most benefit. This may come at an additional expense so I understand why some would choose to take a default route only. --Blake