DHCP Errors post firewall replacement

Posted on 2013-06-28
Medium Priority
Last Modified: 2013-07-11

Ideas why i am seeing bad ip addresses in the dhcp servers at our 2nd site?

We have replaced a like for like cisco asa 5505 firewall.

Question by:CHI-LTD
  • 4

Author Comment

ID: 39284727
LVL 17

Accepted Solution

TimotiSt earned 1000 total points
ID: 39284792
Configuration and firmware version are the same?

Author Comment

ID: 39284840
This hasn't been setup by us, but our managed provider.

I think they copied the config from the old firewall and uploaded.  
Firmware, is newer, i think.
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LVL 20

Assisted Solution

rauenpc earned 1000 total points
ID: 39284941
If they simply copied config, there might be default config left behind. By default the ASA's have a dhcp server configured so that you can plug in on initial boot and use the ASDM. If a simple copy paste was done, it's unlikely that there was any commands in place to remove the default DHCP server configuration. This could mean that many of your clients are receiving an IP from the firewall, and some from the server. Since the server knows nothing about the firewalls leases, all it can do is reactively mark IP's as BAD_ADDRESS meaning that it's a bad address to hand out via DHCP because a device is already using the address. Have your managed provider check if the ASA is handing out an IP it's not supposed to.

The other check you can do would be to stop the DHCP server service, and try to obtain an IP. If you do you will also see which IP is the DHCP server which can't be your server.

Author Comment

ID: 39289722
Ok, they have removed all dhcp rules settings on the firewall but we are still getting all ips in the scope being taken up with bad ip address...

Clients now not picking up ips...

Author Closing Comment

ID: 39317085
Was a leftover dhcp rule and another setting (can't find link now) that caused this.

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