Why Single-Port LAGs?
I recommend always using LACP for external connections. It will make your life easier, even when you only have a single connection. Here’s why we do it.
If you set up a PNI with AS32590, we will strongly recommend the use of LACP, even for a single link. If you have two PNIs with us, they will each be separate single-member LAGs, because they will be on different routers on our side.
It’s only once you have more than 2 links that we start using LACP in the way most people think of it.
It’s not just us. In Google’s Peering Policy, under “Private peering physical connection requirements”, it states
Link aggregation via LACP is required for all links, including single links
Ever wondered why that is? What’s the point in setting up a LAG if I only have one link? What does it give me? More lines of config for no operational enhancement? And I thought we should use L3 everywhere anyway?
I can’t speak for Google, only for the way we operate our network. But I’m pretty sure their reasons are similar to ours. The obvious reason is for future growth, but there are operational benefits too.
