Server handing out different addresses every time??

[Simon Hobson]

Pat Winn wrote:

>Of the ones that do have ping enabled, in the event that the DSL router is
>cold booted, it will always get it's last address (so long as it's still
>a valid lease in the server's memory/leases file). This is presumably due
>to the fact that nobody on the net has his last address and thus, no ICMP
>ping responses come back to the dhcpd when it checks.
>
>The second scenario, which is the one hurting us, is this...
>In the event of a DSL line reset/re-train, the wan interface of the DSL
>router remains "up" and upon completion of the re-train, it sends a
>dhcpdiscover packet to the world in hopes of renewing it's IP address.
>When the dhcpd receives the request, it sends the usual ICMP ping packet
>out and gets a response from the device asking for the address because the
>wan interface thinks it is still up on it's old address for the time being.

So the client is buggy then. If it has an active lease and a 
configured interface, then it should only be sending DHCP-Requests to 
renew that lease. Are these routers you supply, or the customer ? If 
you supply them, then take it up with the manufacturer; if they are 
customer supplied, then get the customer to take it up with the 
manufacturer (give them a prepared technical spiel to send in).

>Since it always, consistently complains that "someone" has that address
>already, it throws it out and offers a new address. This bears the effect
>of handing out a new address *every time* you have a line re-train, where
>if it was just checking the mac address in the ICMP ping reply against the
>one in the current lease on that IP, it would see a match and hand the
>same IP address back to the client rather than tossing it out thinking
>someone else has it and giving him a new IP. This *is* very reproducible.

Not only that, but doesn't it mark the address as abandoned, meaning 
it will only be reused as a last resort when nothing else is 
available. That mean in normal operations, you'll get increased churn 
as recently expired leases will be re-used in preference to 
reclaiming an old abandoned lease.

-- 
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.