• tcpdump - CDP

tcpdump -nn -v -i eth3 -s 1500 -c 1 'ether[20:2] == 0x2000'

Device-ID (0x01), length: 24 bytes: 'nom_du_switch'
Port-ID (0x03), length: 21 bytes: 'GigabitEthernet1/0/10'

• tcpdump - LLDP

[root@ex1dc1dbadm01 ~]# tcpdump  -i eth9 -c 1 '(ether[12:2]=0x88cc or ether[20:2]=0x2000)'
dropped privs to tcpdump
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth9, link-type EN10MB (Ethernet), capture size 262144 bytes
17:12:16.774487 CDPv2, ttl: 180s, Device-ID 'STK-EXADATA-PA3.nibclt.prod', length 429
1 packet captured
2 packets received by filter
0 packets dropped by kernel

• snoop

snoop -d <interface> -x0 -v 'ether[20:2] = 0x2000'

• nmap

nmap -sP 192.168.1.1/24