# I don't fully understand this, can any of you explain please?

Member Posts: 74 ■■□□□□□□□□
Hello everyone! I am studying for my CCENT and I am going through the Lammle book. There is something I don't understand.

Now on managing the configuration register there is this part:

The default configuration setting on Cisco routers is 0x2102. This means that bits 13, 8, and 1 are on, as shown below:

Configuration Register

2. 15 =0/14=0/13=1/12=0/11=0

1. 10=0/9=0/8=1/7=0/6=0

0. 5=0/4=0/3=0

2. 2=0/1=1/0=0

I just don't understand how you know 2 equals 13 or how 1 equals 8 ect. There is something I am missing here, can someone explain it to me? Thanks!

• Member Posts: 103
Because 0x2102 is in Hexidecimal format. Meaning there are 4 bits for each hex number:

2 | 1 | 0 | 2
=
0010|0001|0000|0010

Count backwards starting from the first bit (0). The first, second, and third 1's (on) are 1, 8, and 13.

Hope that makes sense?
• Member Posts: 74 ■■□□□□□□□□
Oh ok, I didn't think to put them all together and break them down into nibbles. I think just the way it was presented in the book threw me off, I figured it was in hexadecimal but just went at it at the wrong way.

Makes total sense now, thank you so much!