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Anonymous
N/A

IP phones not getting dhcp address

Our Cisco 3845 is configured as a DHCP server for the phone vlan, and has been working properly in this capacity since the beginning of time, right up until this morning anyway...  Out of the 90 phones currently deployed in our vlan, 4 were stuck at the "configuring ip" message, and unregistered.  When we did a sh ip dhcp pool on the router, it showed total addresses as 200 and leased addresses at 87.  So we had 117 addresses available.  A sh ip dhcp bindings showed that the addresses in use were scattered across the pool, and that the last address in the scope was in use.  We extended the scope to include more addresses beyond that last address, and the four problem phones immediately configured using ip addresses from the extended range.  We have been adding and removing phones almost daily with no issues until now.  Any ideas?  Is this a bug?  Thanks!

7 REPLIES

Re: IP phones not getting dhcp address

what about DHCP conflicts? If you do a show ip dhcp conflicts do you see a lot of conflicts ?

If a DHCP database agent was not configured, and dhcp conflic logging was not disabled initially, over time leases will be marked as conflicts and start shrinking your DHCP pool.

Anonymous
N/A

Re: IP phones not getting dhcp address

This seems to be the issue - thank you!

Cisco Employee

Re: IP phones not getting dhcp address

I remember something similar in the past and guess we adjusted lease (under dhcp pool)

but more importantly disabled recording of dhcp addr. conflicts using CLI

no ip dhcp conflict logging

IOS DHCP Doc:
http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfdhcp.html

Anonymous
N/A

Re: IP phones not getting dhcp address

Great - thank you for the link!

Anonymous
N/A

Re: IP phones not getting dhcp address

Is there some way to clear out the conflicting addresses to free them up for new leases?

Cisco Employee

Re: IP phones not getting dhcp address

you r welcome....

u may try...

2851-1#clear ip dhcp conflict ?
  *        Clear all address conflicts
  A.B.C.D  Clear a specific conflict

Anonymous
N/A

Re: IP phones not getting dhcp address

Thank you - that's perfect!

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