how Linux Network Configuration

Posted on 2013-02-02
Last Modified: 2013-02-09
Hello everyone,
I'm confused between iptables and route
-I have a fedora server that has 2 interfaces
External : p2p1

Open in new window

Internal : p2p2

Open in new window


Open in new window

The firewall is disable in the server
it pings from server device internal IP to client IP but doesn’t ping from server external IP to client IP
I did the iptables to allow the traffic in the forward chain
# iptables –t nat –A POSTROUTING –o p2p1 –MASQUERADE
#iptables –t nat –A PREROUTING –p tcp –d–dport 80 –j DNAT -–to
#iptable  -A FORWARD –p tcp –d–-dport  80 –j ACCEPT

Open in new window

also changed to enable sysctl net.ipv4.ip_forward=1
after doing these the client can access the internet..
now why do we need route?
And I wish I could use route but I didn’t understand it. I did like that on server but I really don’t understand it and I delete it before doing iptables
route add -net netmask
    gw p2p2

Open in new window

please I am really confused between these if someone can help me. I need my network has more security..
and also I have another a question how can I use my external ip address as DNS.
Thanks guys!
Question by:PCANW
  • 4
  • 2
LVL 77

Accepted Solution

arnold earned 175 total points
ID: 38847666
iptables is a firewall.
route deals with a routing table.

What is this system supposed to do?
Are you trying to set it up as a router to allow traffic between the two segments to pass through the fedora box?
your route directive on the fedora is incorrect.
your routing table on the fedora box should be p2p2 p2p1

within your DHCP configuration you will push the the settings to one side.

You need to be clear what functionality you want to get from this fedora box.
LVL 34

Assisted Solution

by:Duncan Roe
Duncan Roe earned 175 total points
ID: 38847723
iptables is a firewall. Incorrect - it is also a router.
It is indeed confusing that there are routers and route tables, but they are quite separate.
route tables are for how a box routes internally generated IP datagrams: which network interface (NIC) to send them on, what is the address of the gateway (on the local LAN segment unless this box is the gateway)
Gateway and router mean essentially the same thing. iptables rules cause packets coming in from one NIC to be sent out on another. When traffic is toward the Internet, an iptables rule will modify the source address of the outgoing IP datagram to be that of the interface on which it is being sent. This is Network Adress Translation (NAT). When a response datagram is received, the destination address of that datagram is modified to be that of the originating system and the datagram sent out via the NIC on the local LAN. This is Connection Tracking (conntrack)
I've only scratched the surface of what iptables can do. Just remember that route is always internal to the system where it is issued and iptables enables Internet connection.

Author Comment

ID: 38848103
Thanks guys! I really appreciate that
what about DNS?
Connect further...control easier

With the ATEN CE624, you can now enjoy a high-quality visual experience powered by HDBaseT technology and the convenience of a single Cat6 cable to transmit uncompressed video with zero latency and multi-streaming for dual-view applications where remote access is required.


Author Comment

ID: 38848111
oop, I made a mistake. i will correct the point between you guys I will call them to correct that on monday because you all helped me

Thanks again

Author Closing Comment

ID: 38871976
arnold, I think you mean the routing table on the fedora box should be p2p1 p2p2 ? Is that right?
LVL 77

Expert Comment

ID: 38872159

Author Comment

ID: 38872360

Featured Post

Efficient way to get backups off site to Azure

This user guide provides instructions on how to deploy and configure both a StoneFly Scale Out NAS Enterprise Cloud Drive virtual machine and Veeam Cloud Connect in the Microsoft Azure Cloud.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Do you have a windows based Checkpoint SmartCenter for centralized Checkpoint management?  Have you ever backed up the firewall policy residing on the SmartCenter?  If you have then you know the hassles of connecting to the server, doing an upgrade_…
The use of stolen credentials is a hot commodity this year allowing threat actors to move laterally within the network in order to avoid breach detection.
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.
This video gives you a great overview about bandwidth monitoring with SNMP and WMI with our network monitoring solution PRTG Network Monitor ( If you're looking for how to monitor bandwidth using netflow or packet s…

821 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question