Link Layer Discovery Protocol

Link Layer Discovery Protocol (LLDP) is a data link layer protocol that

• enables network devices to communicate their status to other devices on the local network, and
• is enabled by default.

You can use the show lldp neighbors commands to view information about neighbors:

admin@sonic:~$ show lldp neighbors 
------------------------------------------------------------------------------- 
LLDP neighbors: 
------------------------------------------------------------------------------- 
Interface:    eth0, via: LLDP, RID: 2, Time: 0 day, 01:34:39 
  Chassis: 
    ChassisID:    mac cc:d3:42:ca:18:00 
    SysName:      SW17 
    SysDescr:     Cisco IOS Software [Cupertino], Catalyst L3 Switch Software (CAT9K_LITE_IOSXE), Version 17.9.4, RELEASE SOFTWARE (fc5) 
                  Technical Support: http://www.cisco.com/techsupport 
                  Copyright (c) 1986-2023 by Cisco Systems, Inc. 
                  Compiled Wed 26-Jul-23 10:43 by mcpre 
    MgmtIP:       192.168.17.1 
    Capability:   Bridge, on 
    Capability:   Router, off 
  Port: 
    PortID:       ifname Gi1/0/10 
    PortDescr:    GigabitEthernet1/0/10 
    TTL:          120 
    PMD autoneg:  supported: yes, enabled: yes 
      Adv:          10Base-T, HD: yes, FD: yes 
      Adv:          100Base-TX, HD: yes, FD: yes 
      Adv:          1000Base-T, HD: no, FD: yes 
      MAU oper type: 1000BaseTFD - Four-pair Category 5 UTP, full duplex mode 
  VLAN:         20, pvid: yes 
------------------------------------------------------------------------------- 
 
admin@sonic:~$ show lldp table 
  Capability codes: (R) Router, (B) Bridge, (O) Other 
LocalPort    RemoteDevice    RemotePortID    Capability    RemotePortDescr 
-----------  --------------  --------------  ------------  --------------------- 
eth0         SW17            Gi1/0/10        B             GigabitEthernet1/0/10 
-------------------------------------------------- 
Total entries displayed:  1