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DHCP duplicate address error

Hi all

I m running DHCP server in one of our 7200 series router which started giving error logs recently after we added some static NAT statements.

I am attaching the config and also the error log

no ip dhcp conflict logging

ip dhcp excluded-address Y.Y.Y.250 Y.Y.Y.254

ip dhcp ping packets 5


ip dhcp pool interanet

network Y.Y.Y.0

dns-server X.X.X.70 X.X.Z.70

default-router Y.Y.Y.254

lease infinite

ip nat pool internet X.X.X.10 X.X.X.10 netmask

ip nat inside source list 1 pool internet overload

ip nat inside source static tcp Y.Y.Y.252 8080 X.X.X.9 8080 extendable

ip nat inside source static tcp Y.Y.Y.253 1968 X.X.X.60 1968 extendable

ip nat outside source static tcp X.X.X.9 8080 Y.Y.Y.252 8080 extendable

ip nat outside source static tcp X.X.X.60 1968 Y.Y.Y.253 1968 extendable

Aug 5 17:13:46.737 IST: %IP-4-DUPADDR: Duplicate address Y.Y.Y.253 on FastEthernet4/1, sourced by 0004.7673.6418

IOS version :

Cisco Internetwork Operating System Software

IOS (tm) 7200 Software (C7200-JS56I-M), Version 12.1(8a), RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2001 by cisco Systems, Inc.

Compiled Wed 23-May-01 01:49 by yiyan

Image text-base: 0x60008950, data-base: 0x61B54000

is it reqd to hv both inside and outside statements for Static NAT ??

Pls helpe me to avoid getting the error logs ..




Re: DHCP duplicate address error

You dont need both the inside and outside statements. Just the inside statement is enough.

Do you have any of the PCs statically configured with .253 address ? Can you locate the pc with that particular mac address "0004.7673.6418".

Did you get any Duplicate address errors for any other ip addresses other than .253?

Re: DHCP duplicate address error

Hi Shankar

We have assigned .253 to a PC statically and the MAC address belongs to the same PC.

We arent getting any errors except with this IP.



Re: DHCP duplicate address error

Can you check the MAC address of the FE interface and see if it proxies the ARP of that PC (.253).

Try doing a no ip proxy-arp on the FE interface or change the local IP of the PC to a different one and check.



Re: DHCP duplicate address error

Was 253 in the DHCP excluded list before you made the change? Someone might have been given that address with an infinite lease before you took it out for the static use.

Re: DHCP duplicate address error


At present we r not receieing any errors after we remd the eth ip from .253 and configured to .250.

we made seperate exclude commands for .250 to .254.

We hve remd the outside statments too leaving the inside intact.

Thks for all u r help