Classic case of Layer 3 communication failure between bypass AC and SW at a certain site

5840X IRF stacking, connected to core SW

APs went offline in batches, with only some able to reconnect. Investigation revealed that AC and SW could communicate within the same VLAN, but Layer 3 connectivity failed across different VLANs.

1. Debugging IP ICMP on AC // After testing, it was found that AC sent ICMP packets normally but did not receive any replies from SW.

2. SW traffic statistics // The SW side could not capture the ICMP packets from AC.

3. Check the routing table on AC, display ip routing-table // It was found that the next hop of AC was not the VLAN address of the AC device but an abnormal 16-bit mask route.

Later, it was confirmed that the on-site personnel configured an incorrect 16-bit mask address, resulting in a 16-bit route with higher precedence than the default route (0.0.0.0), causing traffic to take the 16-bit mask route first.

However, SW is a 24-bit bitmask route, causing connectivity issues.

Delete the abnormally configured 16-bit bitmask address;