Enabling telnet access for the ASAv

When launching the ASAv in GNS3 by default telnet will partially load and you’ll be welcomed by a blank screen. This has caught me out a few times. The fix is detailed in this excellent blog post.

For posterity to summarise that post. Boot up the ASAv using console type vnc or if you’re on Linux try using spice. Once it’s booted up execute the following command:

ciscoasa#copy disk0:/coredumpinfo/coredump.cfg use_ttyS0

Be careful not to use the letter O it has to be the number 0 at the end of use_ttyS0. Shutdown the ASA, change the console type to Telnet. Power it back on and it should now work.

Formatting a MAC address

I’m often given huge lists of MAC addresses and they tend to arrive in a variety of different formats. Such as the following:

AABBCCDDEEFF
AA-BB-CC-DD-EE-FF
AAB.BCC.DDE.EFF
AABB.CCDD.EEFF
AA:BB:CC:DD:EE:FF

Typically I need them formatted as the last example above, with colons between every 2 characters.

The formula below works great in Excel, where A2 is the cell you’re targeting:

=LEFT(A2,2)&”:”&MID(A2,3,2)&”:”&MID(A2,5,2)&”:”&MID(A2,7,2)&”:”&MID(A2,9,2)&”:”&RIGHT(A2,2)