Cisco 892 interfere with Windows DHCP Server[BAD_ADDRESS]

[Sven Ungerecht]

Hi,

I have trouble with a Cisco 892 Router from my Internet service provider.

Last week we switched from a virtual Router to a hardware Router. But after plugging it in our LAN Switch, the Windows DHCP Server stopped leasing IP's. I got many BAD_ADDRESS with MAC like e1:80:10:ac, e2:80:10:ac, e3:80:10:ac, e4:80:10:ac, e5:80:10:ac, ea:80:10:ac, eb:80:10:ac, ec:80:10:ac and so on.

I do not have access to the Router config, so I can not dump the config to you. We have a flat LAN, single SUB-Net(172.16.0.0/16) and no VLAN, no Spanning Tree. A Keep it Simple, Stupid(KISS) System.

A tech guy from service provider, is telling us, the error is not there fault and my switch is not correctly configured. But this is bullshit. For years we had a another Cisco Router from the precursor ISP and for 2 years the virtual Router from our current ISP. No trouble with my DHCP. But after plugging the new Router in, my DHCP stopped working.

On the 892 is no running DHCP, but something interferences with my Windows Server 2008 R2 SP1 DHCP Server.

I need a tip to confront the tech guy.

Thanks

[Sven Ungerecht]

Maybe I try tomorrow.

I pluged a network tester in the Router, no DHCP found.

[rsims]

By the way, restoring the DHCP server from the DHCP console will fix everything.  I've discovered that if I stopped the dhcp service while tinkering with the router it prevents the bad_address issue.  Like I said I returned the router so I can't do an analysis as to what the issue was, unless the new one does the same thing :(

[rsims]

Hi, I know that this is pretty old, but I'm wondering if you ever discovered the issue?  

We recently received a "new" 1941/k9 but had problems with it because it took cisco/cisco for logging in, but were unable to get into CCP.  Cisco wouldn't give us any support at all because they said the seller wasn't authorized. 

While I was t/s that issue, the exact problem you referenced sprung up.  It took me a while to figure out what was doing it, but it was absolutely the Cisco.  

Basically the issue is that it is causing many if not all of the IP addresses to be detected as duplicates on the network.  Not only was it screwing up my DHCP reservations (with the short mac addresses) and causing it to give BAD_ADDRESS, but it also would prevent us from assigning a static IP to a client.  Any attempt to do so would result in the IP address being listed as "(Duplicate) instead of (Preferred) in ipconfig /all.

It was affecting Windows clients, server, and hardware devices...  Pretty much everything.

I disabled the switch port it was connected to and had to restore my dhcp database (as it had permanently ruined my reservations) and everything returned to normal.

This was a bit terrifying because I could have probably plugged this beast into anybodies network and brought it down...

We had to return the router because of the support issue, but I would like to find the cause of this issue in case it ever happens again, as it would be a real bear to track down had I not known that the Cisco was "new".  

[Sven Ungerecht]

Hi,

I gave up. The router has a few Ports, so everything that needed access to the WAN got it directly. A complete autarkic network.

I cold give it a new try. My DHCP is now 2012 R2 and I have a new Alcatel OmniSwitch 6900 as core.

Sven

[rsims]

You still have it?  I guess the problem went away?