How to check the IP address of an aggregation layer switch

IP addresses on aggregation layer switches can be checked via CLI commands on VLAN interfaces, routed interfaces, or aggregated interfaces, depending on whether the switch operates at Layer 2 or Layer 3.Understanding Aggregation Layer SwitchesAggregation switches consolidate traffic from multiple access switches and forward it to core switches or routers. They often operate at Layer 2 or Layer 3, supporting link aggregation protocols such as LACP or static LAG to combine multiple physical links into a single logical connection, enhancing bandwidth and redundancy . In multi-chassis setups, switches may use MLAG (Arista) or MC-LAG (Juniper) to provide active-active Layer 2 redundancy and efficient bandwidth utilization .Methods to Check IP AddressesLayer 3 Interfaces (Routed Interfaces or SVIs)On Layer 3 aggregation switches, IP addresses are typically assigned to routed interfaces or Switched Virtual Interfaces (SVIs).CLI commands to check IP addresses include:Arista EOS: show ip interface brief or show running-config to view interface IPs and VLAN assignments .Cisco IOS: show ip interface brief or show running-config.Juniper Junos: show interfaces terse or show configuration interfaces .Layer 2 Interfaces in MLAG/MC-LAGFor switches configured with MLAG or MC-LAG, IP addresses are usually assigned to the Routed VLAN Interfaces (RVI) rather than the physical aggregated ports .MAC address tables may show learned MACs on aggregated interfaces, but the IP addresses are tied to the VLAN interface. Use commands like:show arp (to map IPs to MACs on VLAN interfaces)show vlan (to verify VLANs and associated SVIs)Checking Aggregated InterfacesAggregated ports (LAG/LACP) may not have IPs themselves; the IP is assigned to the VLAN interface that the LAG belongs to .Ensure all member ports are up and configured consistently (speed, duplex, VLAN membership) to avoid IP reachability issues .Troubleshooting IP ReachabilityVerify that the VLAN interface is up and has the correct IP.Check MAC and ARP tables to ensure the IP is correctly resolved across MLAG/MC-LAG peers .On Juniper switches, enabling arp-l2-validate can help maintain ARP/MAC synchronization in MC-LAG environments .Practical TipsAlways check the peer link status in MLAG/MC-LAG setups, as the peer link carries control traffic and may affect IP reachability if down .Use ping or traceroute from the switch to verify connectivity to other devices.Document VLAN-to-IP assignments to simplify troubleshooting in multi-chassis environments. By combining interface inspection, VLAN/SVI verification, and ARP/MAC table checks, you can reliably determine and troubleshoot IP addresses on aggregation layer switches in both single and multi-chassis configurations.