Configure DHCP relay (dhcp-helper)

mbox can function as a DHCP relay to forward host/client DHCP requests to an external DHCP server. Please refer to this link for more details on mbox DHCP features.


When configuring dhcp-relay interfaces, following conditions apply:

    • mbox must be reachable to upstream DHCP server

    • can assign dhcp-relay to specific interfaces only

    • when dhcp-relay is configured on the interface, we can not enable dhcp-server (eg. configure mbox to assign IP addresses) on the same interface

NOTE: we can not have both dhcp-server and dhcp-helper running on the same mbox, because both of these services are using the same opening ports (UDP/67/68). mbox can either act as a dhcp-server or dhcp-helper (while dhcp client is supported at all circumstances as this is just a interface specific utility).


    • configure a L2TPv3 tunnel

    • configure VLAN interfaces on LAN ethernet port, assign each VLAN to a bridge

    • configure VLAN interfaces on L2TPv3 tunnel, assign each VLAN to the same bridge


!interface eth1enableip address dhcp-helper!interface vlan 1 200enabledescription "voice vlan"ip address 172.16.1..245/24ip dhcp-helper!

Useful troubleshooting commands:


tcpdump interface xx port 67 (use this to check dhcp request and reply. xx is the interface enabled with dhcp-relay)