DHCP Client Identifier/UID field issue

Jeff Bair jeff_bair at rescomp.berkeley.edu
Mon Aug 16 22:29:50 UTC 2010


I'm currently trying to debug a problem with how our dhcp server populates our dhcpd.leases file and have noticed an interesting issue.  When I populate the dhcp client identifier/uid field with 
a string (more specifically a string that contains an id and a private IP address that is separated by two periods such as '38344..') I have issues when I release the lease and try to 
reacquire another lease using the same hardware address and uid.  According to the dhcp rfc I SHOULD get the same lease back which is what happens when I tried acquiring, releasing, and reacquiring a 
lease without the uid field populated.  However, once I introduce the uid field, even though it's the same uid as before, I receive a different IP address for the lease.  Is there a specific reason 
for this behavior?

What I am currently trying is doing an omapi lookup on the leases file for the hardware address and seeing if there was a previous lease with that hardware-address and seeing if it is free to take 
and simply send a DHCP Request packet for that specific IP address.  This is not as ideal as I have to do an OMAPI lookup each time a user tries to get a lease but the larger problem is that upon the 
second time a user logs in I am unable to do lookups by hardware-address as it says "can't open object: more than one object matches key".  Only one IP address has been put in use so I'm not exactly 
sure why this is occurring since when I do a lookup by uid or IP address it works perfectly fine.  


Jeff Bair
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