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We currently have a DHCP setup that I'm not too fond of.

Two DHCP servers:

  • The first one sends DHCPOFFERs with Proxy IP field only (no IP lease).
  • The second one issues the IP address (Proxy IP empty).

Everything seems to work correctly, but maybe only because the one containing the ProxyIP only is usually faster than the one actually assigning the IP address.

What do you think? (Especially about the part that the two offers are being considered whereas I believe only one should be chosen)

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up vote 6 down vote accepted

What do I think? I think it sounds fragile and harder than required to manage.

Given how often most DHCP clients renew their leases (most are 1-24 hours) and the typical DHCP timeout delays needed to fail the lease obtain/renew I'd care a lot less about any performance issues and more about ensuring it works all the time.

That said you have two machines right now, I'd make use of that. Why not just make each server a normal regular DHCP server doing both jobs and either split the scopes or, if you're using Window, you could even cluster them. This way you get some resilience if one of them fails out of the same hardware you have today which as configured only increases your likelihood of an outage.

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I meant that maybe only the order of things makes it work correctly (currently). In fact, the one issuing the proxy IP is a proprietary machine that we cannot touch like that. But I too believe having those two offers is too fragile. I just need some confirmation. From what I see in the RFCs multiple offers should not be BOTH considered, that's what I'm a little worried about, because here it seems to be that way.... –  Marki Sep 25 '12 at 9:40
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I think you're right to be worried, this setup isn't too common (unless I misread your question anyway). I'm a big fan of simplicity, it's the complexity that bites when you get called out in the night or over holidays. –  Chopper3 Sep 25 '12 at 9:43
    
@Marki, if you are unable to touch the system issuing the proxy address why not simply add the proxy address field to the DHCP server issuing IP addresses and remove the fragility? –  John Gardeniers Sep 25 '12 at 12:11
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Sure, but that system would still be replying to DHCP queries... Thanks for your opinions. I guess I know what to do now. –  Marki Sep 25 '12 at 12:16
    
If you can't touch the proprietary system directly, filter the traffic so DHCP requests don't arrive to it. (or prevent replies from getting out) –  afrazier Sep 25 '12 at 13:41
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