DHCP Troubleshooting & Wireshark

The other day I needed to do some DHCP troubleshooting. I have yet to learn all that tcpdump can do (I know it can do this filtering as well), so I at this time do most of my filtering in wireshark. icon-WireShark

Say you are looking for just the packets pertaining to one particular mac address. You can view these by using the following wireshark filter:

bootp.hw.mac_addr == 00:aa:bb:cc:dd:ee

I have found this to be very useful when I am trying to debug issues client devices maybe having or looking at the dhcp options being sent to a dhcp server.


Resetting Cisco Config to Default

There are a couple of ways you can go about resetting a cisco switch back to its default state, however, I recommend this over doing a write erase.

Simply use the following commands to erase the running configuration and go back to factory state:

delete flash:vlan.dat
erase startup-config


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