Well I am trying to forward packets from the outside world to some machines inside. All machines have real IP's and when I use: -A FORWARD -j ACCEPT everything works fine. But what I want to do is to also filter packets as well as who has access to my internal machines. On Wed 26 Apr 2006 15:57, Aj Mirani wrote: > Why not put something like this into your INPUT chain: > > -A INPUT -p tcp -m tcp --dport 22 -s xxx.xxx.xxx.xxx/28 -d yyy.yyy.yyy.yyy > -j ACCEPT > > Also for your line: > -A INPUT -p tcp --syn -m limit --limit 5/s -i eth0 -j ACCEPT > > This is a server wide limit not a per host limit which depending on what > you're trying to prevent may not be the best way to do it. > > If you are trying to prevent a syn attack but still want the server to > respond to legitimate requests try something like this: > -A INPUT -p tcp -m tcp --tcp-flags SYN,RST,ACK SYN -m recent --set --name > SYNATTACK --rsource -A INPUT -p tcp -m tcp --tcp-flags SYN,RST,ACK SYN -m > recent --update --seconds 20 --hitcount 10 --name SYNATTACK --rsource -j > DROP -A INPUT -p tcp -m tcp --tcp-flags SYN,RST,ACK SYN -j ACCEPT > > This dynamically put hosts on a 'blacklist' who are trying to connect > too fast (more that 10 times in a 20 second period.) with the use of > --update it will keep them blacklisted as long as they continue to send > packets too fast. > > On Tue, Apr 25, 2006 at 04:14:59PM +0300, Stratos Margaritis wrote: > > Can someone help me find out why is this rule does not work? > > > > *filter > > > > :INPUT DROP [1803:271102] > > :FORWARD DROP [0:0] > > :OUTPUT DROP [0:0] > > > > -A INPUT -i lo -j ACCEPT > > -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT > > -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT > > -A INPUT -p tcp -m tcp --dport 25 -j ACCEPT > > -A INPUT -p tcp -m tcp --dport 53 -j ACCEPT > > -A INPUT -p udp -m udp --dport 53 -j ACCEPT > > -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT > > -A INPUT -p icmp -j ACCEPT > > -A INPUT -p tcp -j REJECT --reject-with tcp-reset > > -A INPUT -p tcp --syn -m limit --limit 5/s -i eth0 -j ACCEPT > > -A FORWARD -p tcp -i eth0 -s xxx.xxx.xxx.xxx/28 -o eth1 -d > > yyy.yyy.yyy.yyy -j ACCEPT > > -A FORWARD -j LOG > > > > Where xxx.xxx.xxx.xxx is a real network that should be allowed to contact > > the server yyy.yyy.yyy.yyy both of which are having real IP's. > > > > > > -- > > Stratos > > stratism@xxxxxxxxx -- Stratos stratism@xxxxxxxxx
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