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Need to block wan ip address that ranges from 172.XXX.XXX.80 - 100.

Posted on 2012-03-14
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Last Modified: 2012-03-22
How can I block not just the range of 80 - 100, but the full WAN IP? Can I put a block in the firewall for 172.XXX.XXX.0 and that will cover that whole IP range??
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Question by:jmahlmann
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farzanj earned 125 total points
ID: 37720171
Yes you can.  Which firewall are you using?  A network (Cisco PIX)? Or a Linux firewall??

Warning:  This can cause unexpected problems as it would stop all of your WAN network traffic even DNS lookups.

Allow the addresses you want --your internal address ranges and disallow the rest.

For iptables

iptables -A INPUT -s 172.0.0.0 -j ACCEPT
iptables -A INPUT -s 0/0 -j DROP

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by:HaiFai
HaiFai earned 125 total points
ID: 37720246
Hi

Yes this should work 172.XXX.XXX.0/24 (that 24 is shortcut for mask 255.255.255.0)
or 172.XXX.XXX.0 if you cannot specify mask there.
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by:schmitty007
schmitty007 earned 125 total points
ID: 37720299
Depending on what device you are using as a firewall the steps to apply this filter will be different but, you can block a range of IPs or different subnets with most firewalls by simply entering the IP range or subnet you wish to block.

Example: 172.0.0.0 /8 or 172.0.0.0 255.0.0.0 that will block all 172.x.x.x addresses but the principle applies. A good idea for you might be to download/look up a subneting app either to your phone or on the web and input the IPs you want to block and move the subnet until it best fits the range you want to block.

As poster above has stated this may cause undesirable effects in block web pages or services you don't intend to block.
Also note that 172.16.0.0 to 172.31.255.255 address range is reserved for private use and do not route over the internet. And that subnet is represented by 172.16.0.0/19 or 172.16.0.0 255.255.224.0.
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LVL 62

Assisted Solution

by:gheist
gheist earned 125 total points
ID: 37724276
172.x.x.x may be a RFC1918 address thus really you might need to ask your WAN provider to block martian traffic.
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Expert Comment

by:madunix
ID: 37730969
try to drop the network block on the interfaces of your network router
ip route x.y.z.0 255.255.255.0 Null0
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LVL 62

Expert Comment

by:gheist
ID: 37731389
Normally provider has to do it, but does not hurt if you find they do not. Say mine is leaking 10.x.x.x of their service network all the time...
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