error in BSCI book?

[peterd51]

Hi,

in index C, talking about access lists, it states in a table:

Address Wildcard Mask What It Matches
172.16.8.0/21 0.0.7.255 Any host on subnet 172.16.8.0/21

but with this subnet mask, doesn't it also match any host is the subnets .9.0 to .15.0 ?

Or have it got this completely wrong?

Regards
Peter

 

[KiscoKid]

172.16.8.0/21 includes subnets 172.16.8.0 thru to 172.16.15.0

 

[mainstreetexpress]

Hi, just to recheck subnet masking, the network 172.16.8.0/21 is as follows

Network Hosts: 172.16.8.0
Broadcast Address: 172.16.15.255
usable hosts: 172.16.8.1 172.16.15.254

So yes it will include .9 to .15, but remember that .9 to .15 is already part of the /21 supernet, hence the comment 'Any host on subnet 172.16.8.0/21' is applicable in this case

This is a great netmask calc for complex netmasking

http://www.subnetmask.info/

Mark

 

[peterd51]

Hi,

Ah yes, I can see that now...

for some reason the /21 didn't sink in when I read it and the answer didn't look 'complete'.

Thanks
Peter