01-12-2012 02:31 PM - edited 03-07-2019 04:19 AM
Hello,
I am not sure if this is by design or not but I have dhcp running on my 1841 basically with a 192.168.1.1 - 192.168.1.255 pool. While I do have set excluded ranges I find that the system does not look for any open IP's once it reaches that last IP. For instance while the pool is that large it does end at .180. I would think the system would go back to .1 and look for any IP's that might not be addressed. For instance 192.168.1.2, 192.168.1.3 are not show in the binding table as being used and to me they seem available. Any reason why the system does not use them?
Thank you
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01-13-2012 01:57 PM
Hi,
if you ain't got no dhcp database configured anyway Cisco recommends disabling conflict logging with the no ip dhcp conflict logging command.
All modern OSes should use GARP requests anyway before accepting a DHCP leased address.
Regards.
Alain
01-13-2012 01:10 AM
Hi,
could you do sh ip dhcp conflict
Regards.
Alain
01-13-2012 12:13 PM
At the time of the issue I recieved this and still this:
192.168.1.2 Ping Nov 08 2011 10:45 PM
192.168.1.3 Ping Nov 08 2011 10:45 PM
192.168.1.6 Ping Nov 08 2011 10:45 PM
192.168.1.7 Ping Nov 08 2011 10:45 PM
192.168.1.9 Ping Nov 08 2011 10:45 PM
192.168.1.11 Ping Nov 08 2011 10:45 PM
192.168.1.14 Ping Nov 08 2011 10:45 PM
192.168.1.16 Ping Nov 08 2011 10:45 PM
192.168.1.17 Ping Nov 08 2011 10:45 PM
192.168.1.19 Ping Nov 08 2011 10:45 PM
192.168.1.21 Ping Nov 08 2011 10:45 PM
192.168.1.41 Ping Nov 08 2011 10:46 PM
192.168.1.48 Ping Nov 08 2011 11:11 PM
192.168.1.49 Ping Nov 08 2011 11:11 PM
192.168.1.50 Ping Nov 08 2011 11:11 PM
192.168.1.57 Ping Nov 09 2011 05:35 AM
192.168.1.64 Ping Nov 09 2011 07:20 AM
192.168.1.80 Ping Nov 09 2011 09:37 AM
192.168.1.108 Ping Nov 09 2011 10:28 AM
192.168.1.111 Ping Nov 09 2011 10:28 AM
192.168.1.120 Ping Nov 09 2011 10:39 AM
192.168.1.151 Ping Nov 10 2011 09:48 AM
192.168.1.161 Ping Nov 10 2011 10:03 AM
192.168.1.94 Ping Nov 16 2011 10:05 AM
192.168.1.130 Ping Nov 21 2011 09:44 AM
192.168.1.169 Ping Nov 21 2011 10:49 AM
192.168.1.137 Ping Nov 29 2011 10:46 AM
192.168.1.178 Ping Dec 08 2011 10:36 AM
192.168.1.103 Ping Dec 19 2011 09:52 AM
192.168.1.109 Ping Dec 19 2011 10:10 AM
192.168.1.110 Ping Dec 19 2011 10:10 AM
192.168.1.125 Ping Dec 20 2011 10:43 AM
192.168.1.147 Ping Dec 20 2011 11:00 AM
192.168.1.122 Gratuitous ARP Dec 20 2011 10:15 PM
192.168.1.54 Gratuitous ARP Dec 21 2011 12:10 AM
Take into account the issue or what I feel the issue is was on January 13 2012. I am not sure why there is a gratuitous ARP on those last two IP's though.
01-13-2012 01:05 PM
Hi,
you can clear the IP addresses you are sure are not assigned anymore with the clear ip dhcp conflict
command.
I know clients are using GARP to detect conflicts but apparently the IOS does so in some cases as is stated here:
"
A Cisco router will send out a gratuitous ARP message when a client connects and negotiates an address over a PPP connection. This transmission occurs even when the client receives the address from a local address pool. "
Regards.
Alain
01-13-2012 01:34 PM
Great thanks! I was able to get 30 more IP's back into the pool with that command. Is there anyways to make this automated? I would hate to waste time in checking to see if the IP is active and if not then clearing it out.
01-13-2012 01:57 PM
Hi,
if you ain't got no dhcp database configured anyway Cisco recommends disabling conflict logging with the no ip dhcp conflict logging command.
All modern OSes should use GARP requests anyway before accepting a DHCP leased address.
Regards.
Alain
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