How to debug IP on an aggregation switch

To debug IP issues on an aggregation switch, verify LACP status, check aggregated interface configuration, and monitor traffic using diagnostic commands.Step 1: Verify LACP StatusCheck the status of the link aggregation to ensure that all member ports are correctly aggregated. Use commands such as:FS Switches: debug lacp state, debug lacp errors, debug lacp packet to view LACP negotiation, errors, and packet information .IBM AIX / IEEE 802.3ad: entstat shows LACP status values like Inactive, Negotiating, Aggregated, or Failed, helping identify misconfigured ports or mismatched speeds/duplex .Aruba APs: show ap debug lacp displays LACP activity and packet counts for aggregated ports . Ensure all ports in the aggregation are full-duplex, same speed, and connected peer-to-peer. Mismatched configurations can prevent proper aggregation .Step 2: Check IP ConfigurationOnce LACP is verified, confirm that the aggregated interface has the correct IP address and subnet mask:Use show running-config or show interface to verify IP assignment.Ping the gateway or other devices on the same subnet to test connectivity.If using VLANs, ensure the aggregated interface is assigned to the correct VLAN and that the VLAN is active.Step 3: Monitor Traffic and PacketsUse monitoring tools to ensure traffic flows correctly through the aggregated interface:Cisco Nexus TAP aggregation: Configure a TAP aggregation policy on an IP ACL or MAC ACL to redirect and monitor traffic for troubleshooting .Check for dropped packets or errors on member ports using show interface counters or equivalent commands.For GRE tunnels or encapsulated traffic, verify tunnel IDs and IP encapsulation using show datapath tunnel or show datapath station on Aruba devices .Step 4: Additional TroubleshootingEnsure LACP mode is consistent across switches (Active/Passive).For FortiSwitch, verify LACP fallback mode if connecting to devices not running LACP, and check aggregator selection mode (bandwidth or count) to ensure proper port usage .If aggregation remains in a failed or negotiating state, check for contiguous port requirements and hardware limitations . By systematically verifying LACP, IP configuration, and traffic flow, you can identify and resolve IP issues on an aggregation switch efficiently.