iptables - Allowing Established Sessions?

Posted by Sandro Dzneladze on Super User See other posts from Super User or by Sandro Dzneladze
Published on 2012-07-05T13:15:16Z Indexed on 2012/07/07 21:18 UTC
Read the original article Hit count: 217

Filed under:

iptables

I'm learning how to use iptables on ubuntu server.

Can you please explain to me what "Allowing Established Sessions" means and why should I include it in rules?

sudo iptables -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

I understand concept of allowing specific ports and blocking others

sudo iptables -A INPUT -p tcp --dport ssh -j ACCEPT

block all

sudo iptables -A INPUT -j DROP

But I don't get the concept of allowing established session.

Thanks.

S.

Related posts about iptables

Sometimes this script fails to update the iptables

as seen on Server Fault - Search for 'Server Fault'
It does not happen often, but sometimes after running the below script, checking the iptables with service iptables status shows that they weren't updated and the script doesn't output any error. The iptables is structured as look-up tree (long repeated sections snipped): #!/bin/sh iptables -t… >>> More
My current iptable configuration doesn't work [on hold]

as seen on Server Fault - Search for 'Server Fault'
sudo chkconfig iptables off /etc/init.d/iptables on ### Clear/flush iptables sudo iptables -F sudo iptables -P INPUT ACCEPT sudo iptables -P OUTPUT ACCEPT sudo iptables -P FORWARD ACCEPT ### Allow SSH iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT iptables… >>> More
L2TP iptables port forward

as seen on Server Fault - Search for 'Server Fault'
Hi all, I'm setting up port forwarding for an L2TP VPN connection to the local Windows 2003 VPN server. The router is a simpel Debian machine with iptables. The VPN server works perfect. But I cannot log in from the WAN. I'm missing something. The VPN server is using a pre-shared key (L2TP) and… >>> More
iptables -P FORWARD DROP makes port forwarding slow

as seen on Server Fault - Search for 'Server Fault'
I have three computers, linked like this: box1 (ubuntu) box2 router & gateway (debian) box3 (opensuse) [10.0.1.1] ---- [10.0.1.18,10.0.2.18,10.0.3.18] ---- [10.0.3.15] | box4, www [10.0.2.1] Among other… >>> More
IPtables AWS EC2 NAT/Reverse NAT - For Reverse Proxy style setup but with IPtables

as seen on Server Fault - Search for 'Server Fault'
I was thinking initially needing to do a reverse proxy or something so I could get some SSL/TLS traffic look like it is being terminated at a server and IP address in the AWS cloud, and then that traffic is forwarded onto our actual web servers that aren't in the cloud... I've not done much iptables… >>> More

Developer IT

iptables - Allowing Established Sessions? - Developer IT

iptables - Allowing Established Sessions?

iptables

Related posts about iptables

Sometimes this script fails to update the iptables

My current iptable configuration doesn't work [on hold]

L2TP iptables port forward

iptables -P FORWARD DROP makes port forwarding slow

IPtables AWS EC2 NAT/Reverse NAT - For Reverse Proxy style setup but with IPtables

Categories cloud