Option 82 isc-dhcp-server

Посмотреть, что прилетает от свича можно с помощью tcpdump:

tcpdump -n -i eth3 -s 0 -v -vv port 67

20:53:03.846706 IP (tos 0x0, ttl 30, id 24370, offset 0, flags [none], proto UDP (17), length 345)
10.100.0.1.68 > 10.100.254.254.67: [udp sum ok] BOOTP/DHCP, Request from b8:69:f4:f6:ce:c8, length 317, hops 1, xid 0xac72323f, secs 38, Flags [Broadcast] (0x8000)
Gateway-IP 10.100.0.1
Client-Ethernet-Address b8:69:f4:f6:ce:c8
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Discover
Parameter-Request Option 55, length 8:
Subnet-Mask, Classless-Static-Route, Default-Gateway, Static-Route
Domain-Name-Server, NTP, Option 138, Vendor-Option
Hostname Option 12, length 8: “MikroTik”
Client-ID Option 61, length 7: ether b8:69:f4:f6:ce:c8
Agent-Information Option 82, length 15:
Circuit-ID SubOption 1, length 5: port1
Remote-ID SubOption 2, length 6: switch
END Option 255, length 0
PAD Option 0, length 0, occurs 27