Network Layer Troubleshooting

Mismatched Maximum Transmission Unit (MTU)

If a router with a higher MTU sends a packet to a router with a lower MTU, the receiving router will attempt top fragment the Packet

If the packets “Don't Fragment bit is set, the Router will drop the packet and send a ICMP message about the reason

If the router has been configured not to send out ICMP messages for dropped packets, you have a Black Hole Router Situation