Great post. This is a very clear explanation of the routing situation. The last image is especially good. What's needed is some kind of L2 Traceroute. It's mad

Great post. This is a very clear explanation of the routing situation. The last image is especially good. What's needed is some kind of L2 Traceroute. It's maddening that an increasingly common piece of routing infrastructure is invisible to almost all common troubleshooting tools. Edit: Cisco has one for their routers [0]. Since each hop would have to be traced locally, an L2 Trace would require orchestrating against all hardware devices in the route which introduces legal complications. A new discovery protocol might be needed. [0] https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SXF/native/configuration/guide/swcg/l2trace.html https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6...