Если в сети гуляет LLDP, то можно и посмотреть чем оборудование обменивается.
 

tcpdump -v -s 1500 -c 1 '(ether[12:2]=0x88cc or ether[20:2]=0x2000)' -i eth0

Примерный вывод:
 

22:55:25.718424 LLDP, length 237
Chassis ID TLV (1), length 7
Subtype MAC address (4): 00:12:cf:c1:a6:f6 (oui Unknown)
Port ID TLV (2), length 7
Subtype MAC address (3): 00:12:cf:c1:a6:f9 (oui Unknown)
Time to Live TLV (3), length 2: TTL 120s
Port Description TLV (4), length 32: Ethernet Port on unit 1, port 52
System Name TLV (5), length 18: street-1-dom-2-pod-3
System Description TLV (6), length 7
ES3552M
System Capabilities TLV (7), length 4
System Capabilities [Bridge] (0x0004)
Enabled Capabilities [Bridge] (0x0004)
Management Address TLV (8), length 12
Management Address length 5, AFI IPv4 (1): 192.168.50.30
Interface Index Interface Numbering (2): 1050
Organization specific TLV (127), length 6: OUI Ethernet bridged (0x0080c2)
Port VLAN Id Subtype (1)
port vlan id (PVID): 1
Organization specific TLV (127), length 18: OUI Ethernet bridged (0x0080c2)
VLAN name Subtype (3)
vlan id (VID): 1
vlan name: DefaultVlan
Organization specific TLV (127), length 21: OUI Ethernet bridged (0x0080c2)
VLAN name Subtype (3)
vlan id (VID): 13
vlan name: Vlan_13_kor2_2
Organization specific TLV (127), length 14: OUI Ethernet bridged (0x0080c2)
VLAN name Subtype (3)
vlan id (VID): 14
vlan name: Vlan_14
Organization specific TLV (127), length 13: OUI Ethernet bridged (0x0080c2)
VLAN name Subtype (3)
vlan id (VID): 50
vlan name: upravl
Organization specific TLV (127), length 7: OUI Ethernet bridged (0x0080c2)
VLAN name Subtype (3)
vlan id (VID): 4093
vlan name:
Organization specific TLV (127), length 7: OUI Ethernet bridged (0x0080c2)
Protocol Identity Subtype (4)
protocol identity: \0x88\0xcc
Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
MAC/PHY configuration/status Subtype (1)
autonegotiation [supported, enabled] (0x03)
PMD autoneg capability [10BASE-T hdx, 10BASE-T fdx, 100BASE-TX hdx, 100BASE-TX fdx, 1000BASE-T fdx] (0x6c01)
MAU type 1000BASET fdx (0x001e)
Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
Link aggregation Subtype (3)
aggregation status [supported], aggregation port ID 0
Organization specific TLV (127), length 6: OUI IEEE 802.3 Private (0x00120f)
Max frame size Subtype (4)
MTU size 1522
End TLV (0), length 0
1 packet captured

Еще один пример:
 

22:52:02.927231 CDPv1, ttl: 120s, checksum: 0xd363 (unverified), length 71
Device-ID (0x01), value length: 8 bytes: 'MikroTik'
Address (0x02), value length: 13 bytes: IPv4 (1) gateway
Port-ID (0x03), value length: 6 bytes: 'wlanbr'
Capability (0x04), value length: 4 bytes: (0x00000001): Router
Version String (0x05), value length: 4 bytes:
5.19
Platform (0x06), value length: 8 bytes: 'MikroTik'