topic Re: HowTo handle DHCP Log reverse IP addresses in Splunk Search

HowTo handle DHCP Log reverse IP addresses

tyralla — Thu, 04 Oct 2012 08:05:44 GMT

Hi,

I'm looking for a possibility to join DHCP events together with transaction command. Join fields are IP and MAC address.

Unfortunately DHCP Log contains in some cases the IP in reverse.
As an example:

TIMESTAMP,DNS Update Request,66.1.168.192,MachinName,,

Correct IP in this case would be 192.168.1.66.

Is there any way to reverse the IP to allow matching with the rest of the IP entries in this field?

Thanks!

Re: HowTo handle DHCP Log reverse IP addresses

Ayn — Thu, 04 Oct 2012 08:15:47 GMT

Yeah I've seen that too, Microsoft's DHCP server seems to have a weird behaviour with that.

If you have the original IP in a field, let's call it ip, you could reorder the octets with a rex statement.

... | rex mode=sed field=ip "s/(\d+)\.(\d+)\.(\d+)\.(\d+)/\4.\3.\2.\1/"

Re: HowTo handle DHCP Log reverse IP addresses

tyralla — Thu, 04 Oct 2012 14:34:36 GMT

Works perfect - Thanks!