dhcp.conf relay howto?

Chuck Anderson cra at WPI.EDU
Tue Apr 24 14:50:47 UTC 2007

On Tue, Apr 24, 2007 at 09:55:36AM -0400, Edwin Whitelaw wrote:
> My dhcp server has multiple subnets on eth1 and it's correctly 
> configured using shared-network for the locally attached clients.  If 
> the remote dhcrelay host also comes in on eth1, should the subnet 
> declaration for the remote network also go inside the shared-network?

No.  Remote networks which are relayed by a DHCP relay agent have the 
giaddr set to the IP address of the relay agent's interface in that 
remote subnet.  The DHCP server uses the giaddr to match a subnet 
block.  Local subnets do not have giaddr set (or rather it is 
in which case the DHCP server uses the local network interface's 
network address and subnet mask to match the incoming requests to a 
shared-network or subnet block.

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