UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict

Asim Afzal · ‎06-20-2012

I have DHCP scope configured on my Core swtich.After i rebooted my core swtich i can see dhcp conflicts error messages .Any way to void these conflict if another reboot of switch happens

Jun 7 23:36:22.662 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.33.

Jun 7 23:36:27.662 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.36.

Jun 7 23:36:29.162 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.37.

Jun 7 23:36:30.162 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.38.

Jun 7 23:36:37.662 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.42.

Jun 7 23:36:39.162 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.43.

Jun 7 23:36:42.662 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.45.

Jun 7 23:36:51.662 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.50.

Jun 7 23:36:52.666 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.51.

Jun 7 23:37:02.166 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.56.

Jun 7 23:37:11.166 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.61.

Jun 7 23:37:12.170 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.62.

Jun 7 23:37:13.670 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.63.

Jun 7 23:37:18.670 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.66.

Jun 7 23:37:25.670 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.70.

Jun 7 23:37:30.670 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.73.

Jun 7 23:37:47.670 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.82.

Jun 7 23:37:48.674 UAE: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged 10.15.241.83

Peter Paluch · ‎06-20-2012

Hello Asim,

These messages are caused by the fact that in default configuration, the DHCP lease record (which station was assigned which IP address) are held only in the RAM of the router or switch. When you reload it, these leases are forgotten, and when DHCP server starts assigning IP addresses anew, it may try to assign an address that is already being used (assigned previously). Hence the messages.

The only solution is to configure a permanent storage for the leases. This is called DHCP Server Database. Information about this functionality and the configuration can be found, for example, here:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_58_se/configuration/guide/swdhcp82.html#wp1353953

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_58_se/configuration/guide/swdhcp82.html#wp1354092

In short, the idea is to have the switch store these leases permanently to a network-accessible server via TFTP, FTP or HTTP. When the switch reloads, it downloads the stored leases file and continues assigning the addresses appropriately.

Best regards,

Peter