11-17-2008 09:01 PM - edited 03-06-2019 02:32 AM
Hi Group,
I have a query regarding DHCP conflicts. One of our customer is using Cisco 4500 switches in Core/Distribution and these switches are running DHCP service as well. There is one DHCP Pool configured for IP Phones (172.21.17.0/24). Yesterday we got compalint from cutomer that IP Phones are not able to get IP address so I checked the primary 4500 switch and found 'DHCP conflict' log messages so I used ' claer ip dhcp conflict *' command and after that all IP Phones started getting ip addresses.
What could be the possible cause of this problem ? Should we disable logging of DHCP conflicts ?
Can we avoid such incident by using 'ip dhcp ping' command ? Kindly guide me in this reagrd.
Thanks in Advance.
Regards,
Mujeeb
11-18-2008 05:44 AM
1) Have you configured the same pool range on two switches ?
2) Are you sure there is no "rogue" dhcp server in the subnet ?
11-18-2008 06:23 AM
Hello Mujeeb,
>>Should we disable logging of DHCP conflicts ?
No, this allowed you to detect the problem it isn't the problem cause it is handy to detect the problems.
Are both C4500 serving the same address pool ?
Hope to help
Giuseppe
11-18-2008 08:11 AM
Hi,
Yes, DHCP pool on both primary and secondary switches is same. Primary switch is the root switch for all Vlans. Below is the log message for your reference,
%DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 172.21.17.185
Thanks & Regards,
Mujeeb
11-18-2008 08:19 AM
Hi,
Here is a CORRECTION that secondary switch is the root switch for few VLANs.
Regards,
Mujeeb
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