Enabling DHCPd listen on dynamically generated interfaces

Simon Hobson dhcp1 at thehobsons.co.uk
Tue May 1 18:45:23 UTC 2012

Shankar wrote:

>  >Have you considered using a relay agent instead ? That way you can
>>keep the server running. I don't think you'll be able to run one
>>relay agent per client connection because of the need for each one to
>>listen on the connection to the server.
>>BTW - what is the interface type that's dynamically generated ? I'm
>>assuming not PPP since I didn't think the ISC server works on those.
>They are l2tp tunnels, which gets established and tore down dynamically.

Ah, didn't think of those.

>Do we've need 'dhcp relay' when server to remote client is over pure L2 ?.
>Reason being, when client send "DHCPDISCOVER", I see them on respective
>tunnels @ Debian box.

What I was thinking is that the startup time for a relay should be 
quicker than for the server. So if you could leave the server running 
(on a separate machine) and run a relay agent on your gateway then 
the downtime would be a lot less.
Even more ideal would be the ability to start a relay instance for 
each dynamic interface (thus there'd be no interaction between 
interfaces) - but I'm fairly certain that isn't possible since they'd 
all have to listen on the same interface to talk to the server. 
Unless someone knows differently ...

Simon Hobson

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