The Infinite Loop

A routing loop happens when Router A sends to Router B, and Router B sends back to Router A.

Symptoms:

• Ping returns "TTL Exceeded".
• Traceroute shows the same two IPs repeating: 10.0.1.1, 10.0.2.1, 10.0.1.1...

Common Cloud Causes:

Transit Gateway Misconfiguration: You attach VPC A and VPC B. In VPC A's route table, you send 10.0.0.0/8 to TGW. In TGW route table, you accidentally send 10.0.0.0/8 back to VPC A attachment.

BGP Route Leaking: Advertising a route learned from a provider back to the same provider.