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Full Discussion: iptables in a NAT scenario
Special Forums Cybersecurity iptables in a NAT scenario Post 302808751 by capri_guy84 on Friday 17th of May 2013 12:16:31 PM
Old 05-17-2013
iptables in a NAT scenario

Hi, I am learning IPTables have this question.

My server is behind a firewall that does a PAT & NAT to the LAN address.
Code:
Internet IP: 68.1.1.23
Port: 10022

Server LAN IP: 10.1.1.23
port: 22

Allowed Internet IPs:  131.1.1.23, 132.1.1.23

I want to allow a set of IPs are to be able to SSH & DROP all other traffic. The question where I got confused is my destination address

Packet from computer on Internet:
Code:
Source IP: 131.1.1.23            sourceport:<random>
Destination IP: 68.1.1.23        destinationport: 10022

Packet seen by server behind firewall:
Code:
source IP: 68.1.1.23   sourceport: 2522
destinatation IP: 10.1.1.23   destinationport: 22

Q1) Now, how do I write my IPtables ruleset, if the host is not able to see the actual source of the traffic?

Q2) I also want to block any SSH from within 10.0.0.0/subnet as it will be a colo facility & other servers share LAN addresses.
 

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IPTABLES-SAVE(8)                                                  iptables 1.6.1                                                  IPTABLES-SAVE(8)

NAME
iptables-save -- dump iptables rules to stdout ip6tables-save -- dump iptables rules to stdout SYNOPSIS
iptables-save [-M modprobe] [-c] [-t table] ip6tables-save [-M modprobe] [-c] [-t table] DESCRIPTION
iptables-save and ip6tables-save are used to dump the contents of IP or IPv6 Table in easily parseable format to STDOUT. Use I/O-redirect- ion provided by your shell to write to a file. -M, --modprobe modprobe_program Specify the path to the modprobe program. By default, iptables-save will inspect /proc/sys/kernel/modprobe to determine the exe- cutable's path. -c, --counters include the current values of all packet and byte counters in the output -t, --table tablename restrict output to only one table. If not specified, output includes all available tables. BUGS
None known as of iptables-1.2.1 release AUTHORS
Harald Welte <laforge@gnumonks.org> Rusty Russell <rusty@rustcorp.com.au> Andras Kis-Szabo <kisza@sch.bme.hu> contributed ip6tables-save. SEE ALSO
iptables-apply(8),iptables-restore(8), iptables(8) The iptables-HOWTO, which details more iptables usage, the NAT-HOWTO, which details NAT, and the netfilter-hacking-HOWTO which details the internals. iptables 1.6.1 IPTABLES-SAVE(8)
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