Peering Policies and Route Servers

  Luckily this sort of breakage does not happen very often.
  Unluckily, if it does break, if can be really hard to diagnose.

Especially in the presence of a TelCo-supplied level 2 switching
fabric like Frame Relay, SMDS, or ATM.

No kidding. Or ethernet briding over ATM PVCs. Think of OSPF or
ISIS and designated routers on not quite ethernets and the interesting
things that can happen in face of partial connectivity (or half
duplex PVCs). -:slight_smile: (Andrew Partan)