No TCP/ IP Connection

** TROUBLESHOOT THE NETWORK CONNECTIONS FIRST **

You CANNOT troubleshoot BGP if you don't have a stable physical link and TCP cannot establish a connection.

Why is all this in big bold letters?

1. You must have a green light on your CSU/DSU (or DSL, FRAD or ISDN modem etc.). The green light only means the physical layer and data link layer are working.
2. IP is a Network Layer protocol. IP can't run if the physical link isn't working and PING will fail if IP is not properly configured.
   1. You need an IP address
   2. You need to make sure the mask is the same on both sides of the circuit
   3. You need to be sure that your router knows how to reach the IP address at the far end of the circuit.
3. TCP is a transport layer protocol and runs over IP. If you can't establish a TCP connection you can't communicate TCP transported data.
4. BGP is effectively an Application layer protocol and runs on TCP over IP. No TCP, IP or physical/data link layer connectivity equals no BGP communication.
5. ICMP PING does not need BGP to ping your ISP's router on the other side of an IP connection. If you cannot PING, you have bigger problems than BGP and need to fix the link itself.