Hi, If the DHCP-server doesn't provide the option DHO_DHCP_SERVER_IDENTIFIER, the broadcast address is used as fallback (see state_bound). However, things are different when sending DHCP-release. If the option DHO_DHCP_SERVER_IDENTIFIER is missing, INADDR_ANY is used resulting in an error ENETUNREACH.
Suggestion: use broadcast address instead (like the isc does) Code excerpt: sbin/dhclient/dhclient.c void release_lease(struct interface_info *ifi) { ... opt = &ifi->active->options[DHO_DHCP_SERVER_IDENTIFIER]; if (opt->len == sizeof(in_addr_t)) ifi->destination.s_addr = *(in_addr_t *)opt->data; else ifi->destination.s_addr = INADDR_ANY; /* INADDR_BROADCAST??? */ Best, Alex