A DHCP Relay agent relays DHCP requests from the client to the DHCP server, and relays the DHCP replies from the server to the client. It acts as a proxy, and can reduce the number of DHCP servers required in the network. The DHCP relay agent inserts its own IP address in the giaddr field (gateway address) of the DHCP request. The DHCP server looks into this IP address, identifys the DHCP client‘s subnet, and assigns an IP address accordingly.
The ExtremeXOS BOOTPRelay module is Extreme Networks' DHCP Relay agent. It is now enhanced to optionally insert the secondary addresses of the interface.
DHCP clients can now be dynamically assigned both public and private addresses in an effort to reduce administrative overhead. ExtremeXOS can now configure the BOOTPRelay agent to insert both primary and secondary address(es) of the client-facing interface as a gateway address in the DHCP packet. At any given point in time, the DHCP client can be assigned one IP address.
The DHCP server has the responsibility to assign the correct IP address in the correct subnet by choosing the DHCP DISCOVER packet to respond to. Similarly, the DHCP client is responsible for accepting the appropriate DHCP OFFER from the DHCP server.
NoteOnly the DHCP DISCOVER request is sent in multiple copies, with different IP addresses as the gateway address in each. All other DHCP packets are relayed normally.
The relay agent receives a DHCP DISCOVER request and inserts the primary address of the client-facing interface as the gateway address, and relays this packet to the server. The switch counts the number of times a DHCP client sends out a DHCP request without receiving a DHCP OFFER message. After three retries, the relay agents sets the secondary address as the gateway address in the next DHCP Discover request that gets relayed. If the DHCP server still does not respond after three retries, the next secondary address is used as the gateway address, and so on cyclically.
Issue the following commands to configure te DHCP Smart Relay feature:
This feature is supported on all platforms.