Toujours aucun réponse à requêtes DHCP malgré la modification que tu as indiquée, voici l'extrait tcpdump :
0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 44:d9:e7:41:3a:eb (oui Unknown), length 319, xid 0xe2580d0, secs 46, Flags [none]
Client-Ethernet-Address 44:d9:e7:41:3a:eb (oui Unknown)
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Discover
Hostname Option 12, length 4: "ubnt"
Parameter-Request Option 55, length 5:
Lease-Time, RN, RB, Option 119
AUTH
Vendor-Class Option 60, length 5: "sagem"
Client-ID Option 61, length 7: ether XX:XX:XX:XX:XX:XX
User-Class Option 77, length 44:
instance#1: "FSVDSL_livebox.Internet.softathome.Livebox3", length 43