Access-lists

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sorry for thread jackin.
But does muckyfingers or any other have a special way for summarizing which network a router will advertise on its serial

if it has

network 172.16.16.0/24
network 172.16.17.0/24
network 172.16.18.0/24
network 172.16.19.0/24

on it ethernet ports

answer is 16.0/22 i know but if theres a super quick way like with access lists :>

 

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I will have to re-read over this subject but I would think you are just trying to mask out all the similar bits.

So

172.32.16.0
172.32.17.0
172.32.18.0
172.32.19.0

would have the following in common:

1st and 2nd octet are the same so cound those bits = 16
3rd octet would look like this:

0001 0000
0001 0001
0001 0010
0001 0011

so the 1st 6 bits in the 3rd octet are similar so add that to the 16 and you got 22 bits.

172.32.16.0 /22

but I am going to look over some of my books again. I am really really impressed with the Cisco Academy Companion Books. Gonna have to read them cover to cover.

 

Back on ACLs I came across a similar question as before. It goes something like this:

Which wildcard mask will enable a network administrator to permit access to the internet for only hosts that are assigned an address in the range 205.25.8.0 through 205.25.15.255 ?

I used Muckyfoot's method and came up with: 0.0.7.255

Took me about 3 seconds.