It's never too late!
As for subnetting, after a few methods I have found this to be the best:
167.12.155.16 /20 ...find the subnet.
first:
/20 = 255.255.240.0 ...how? each octet is 255 so we count the bits:
255 = 11111111 in binary
254 = 11111110
240 = 11111100
...and so on...
we now know that 11111111.11111111.11111100.00000000 is 255.255.240.0, just add up the 1s to get the /20.
Now we can go further;
circle the .155 and the .240
Our 'magic' number is 256 when subnetting so, subtract 240 from 256 = 16
16 into 155 (the 3rd octet of the IP) without going over is 144.
The answer is 167.12.144.0
Holy crap I haven't done Subnetting in a loong time (back in High School I did two years of it but never tested for it...).
I have been thinking of getting into IT certs again, and have printed out the A+ manual to read and pass, then I plan on doing the same thing with Net+ and finally move back into the CCNA.
The only hard part is that I have no money to take a class so I can't play with a router, granted I am thinking of trying to get a job at a local internet company and trying to get them to pay for it