172 addresses

[sirugo]

I have a php-script that checks whether a user is coming from inside our firewall (using a 172-address) or if he's coming from the outside (any other address). Certain restrictions appear for outside users.

But is it possible for an outside user to change his IP-address to appear as a 172-address in any way or are all 172-addresses always for inside-users?

 

[jimbopalmer]

http://www.cartalk.com/content/columns/Archive/2006/May/06.html

so 172 addresses outside of 172.16.0.0 - 172.31.255.255 would be legal Internet addresses, not internal.

I tried to remain child-like, all I acheived was childish.

 

[sirugo]

OK
We have 172.16 addresses internally.
But with what did that url help us out?

 

[jimbopalmer]

Sorry, I thought you asked 'are all 172-addresses always for inside users?' so I showed you that they weren't.

Only the one range of 172.16 to 172.31 is internal, the rest of the 172 addresses are external.

I tried to remain child-like, all I acheived was childish.

 

[sirugo]

OK, but the 172.16-series is fail safe?

 

[pansophic]

172.16 - 172.31 are RFC 1918 Private Network Addresses. All 172.x.x.x addresses outside of those ranges are legal internet addresses.

You need to change your filter on your php script to match against 172.16, rather than all 172 addresses.


pansophic