Configure DHCP relay (dhcp-helper)

mbox can function as a DHCP relay to forward host/client DHCP requests to an external DHCP server.

dhcp.png

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).

CONFIGURATION STEPS

    • 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

CONFIGURATION EXAMPLES

=========================!interface eth1enableip address 10.89.4.245/24ip dhcp-helper 202.10.10.99!interface vlan 1 200enabledescription "voice vlan"ip address 172.16.1..245/24ip dhcp-helper 202.10.10.99!

Useful troubleshooting commands:

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