IP conflict detected by router, but on broadcast address (.255). What does this mean?

Posted on 2013-09-30
Medium Priority
Last Modified: 2013-10-12
We have a user who has developed a network problem. Their original complaint was that at times suddenly their laptop would drop off wireless.
A computer in another room was OK and sometimes they would take their laptop into another room served by another wireless access point and it would come back online.

On the network itself, if you run a continuous ping, there are quite a few dropped packets and slow response times.  This is not the case if you detach the router from the switch and hook up to the router directly.

We have a Draytek 2830 router in this case, and one thing of note was that in the DHCP table it reports conlflicted IP address, however on the broadcast address.

For example,

The thing is, it’s saying there are conflicted IP’s on what I understand to be the broadcast address.
What does this mean in the real world? Is there another DHCP server on the network or something?
Question by:afflik1923

Expert Comment

ID: 39535676

Seems to be the DHCP configuration put the entire rage of subnet in to the pool.!

for clarification, can we have the DHCP pool running configuration?  

LVL 47

Expert Comment

by:Craig Beck
ID: 39536005
What's the IP address and subnet mask of the LAN on the Draytek router?

Author Comment

ID: 39536034
The IP address of the router is: (one of the ones reported in conflict).
However, we think the CONFLICT issue may be a red herring as the firmware is from 2010 so we are going onsite to update this.

I did not really understand the previous question
"can we have the DHCP pool running configuration"

Thanks so far and will keep updated.
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LVL 57

Expert Comment

ID: 39536775
He wants to see the DHCP pool definition.  More specifically what is your network mask.

An IP network's broadcast address is based on the mask mask.  Example:

If you have the broadcast address would be

However say you setup, then would be a valid IP address and the broadcast address for the network would be with an IP address range of

Accepted Solution

afflik1923 earned 0 total points
ID: 39536925
OK well in this network it uses the standard DHCP subnet for a DRaytek and many other routers so is

Since upgrading the firmware, it not longer mentions the IP Conflict, so it may have been a simple one on that specific issue.
however there are still signs of network issues based on that when you run a continuous ping to google.co.uk, packets are dropped and some take a long time to response.

But at least we will analyse the problem with the switches and router having the latest firmware.
LVL 34

Expert Comment

ID: 39553411
You provided the subnet mask... we're looking for the range of IP addresses that can be assigned out by DHCP.

Author Closing Comment

ID: 39567878
Thanks for all the input on this. In the end it seems the issue was down to a required firmware upgrade.

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