При ближайшем рассмотрении, обнаружено, что дело не в типе пакета ответа, а в его отсутствии.
Проверено на двух моделях DES-1210-28/ME/B2 (Fimware: 6.07.B064, 6.07.B086, 6.09.B008) и на DES-3200-10 Rev.C (Firmware: 4.39.B010).
Проблемное устройство: eltex rg-2404g-w.
При подключению к свитчу другого вендра со включенным релеем, tcpdump на eltex показывает:
Код:
07:00:57.070000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:00.080000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:03.090000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:03.120000 70:72:cf:92:07:bf (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 342: 10.0.24.28.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300
07:01:03.120000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 341: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 299
07:01:03.150000 70:72:cf:92:07:bf (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 342: 10.0.24.28.bootps > 255.255.255.255.bootpc: BOOTP/DHCP, Reply, length 300
При подключении к указанным моделям свитчей длинка видем только постоянные запросы:
Код:
07:00:57.100000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:00.110000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:03.120000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:06.130000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:09.140000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:12.150000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:15.160000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
07:01:18.170000 a8:f9:4b:03:ca:ee (oui Unknown) > Broadcast, ethertype IPv4 (0x0800), length 329: 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from a8:f9:4b:03:ca:ee (oui Unknown), length 287
При этом в логах DHCP сервера видим, что ответ уходит. При подключении другого устройства в этот же порт адрес выдаётся.