Check the IP address of connected devices on the access switch

You can identify IP addresses of devices connected to a switch by correlating MAC addresses from the switch's MAC table with ARP entries, or by using DHCP snooping and IP client-tracker features on supported switches.

Using MAC Address and ARP Tables

For Cisco switches, the most common method involves a two-step process: Retrieve MAC addresses of devices connected to switch ports using the command show mac address-table. This maps each MAC address to a specific physical port on the switch.

Correlate MA

C addresses with IP addresses by checking the ARP table on a router or Layer 3 switch using show arp. This allows you to determine the IP address associated with each MAC. This method works recursively in networks with multiple switches: first identify the MAC on the uplink interface, then log into the access switch to find the exact port.

Using DHCP Snooping and I

P Client-TrackerFor switches that support these features (e.g., HPE 2540, 2920, 2930, 3810, 5400R): DHCP Snooping: Enable globally and on the VLAN where clients reside. Trusted uplink ports must be configured to allow DHCP packets. Use show dhcp-snooping to view learned IP addresses.

IP Client-

Tracker: Configure with ip client-tracker trusted or untrusted to track authenticated or unauthenticated clients. Use show port-access clients to list IP addresses per port. Older switch models may only support DHCP snooping, while newer models support both methods.

Using Switch-

Specific Commands

Cisco: show ip interface brief shows the switch's management IP, while show mac address-table and ARP correlation reveal connected device IPs. Huawei: display arp lists IP addresses and the interfaces they are connected to.

For VLA

N or bridge-domain interfaces, additional commands like display vlan vlan-id or display bridge-domain bd-id provide detailed port mapping.

Additional Considerations

Ensure the switch has an IP address in the same VLAN as the devices to enable ARP-based tracking. For Layer 2 switches without IP configuration, IP tracking may require DHCP snooping or client-tracker features. Network management systems (NMS) can automate IP discovery across multiple switches.

By combining these methods, you can accurately determine which IP addresses are associated with each switch port, regardless of switch model or network topology.