LinuxQuestions.org
Help answer threads with 0 replies.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Networking
User Name
Password
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.

Notices

Reply
 
Search this Thread
Old 07-18-2003, 10:37 AM   #1
varunbihani
Member
 
Registered: Jul 2003
Location: indore, india
Posts: 69

Rep: Reputation: 15
Internet Sharing on Linux machines


I have 3 Linux RH 9 machines in my LAN.
I want to access internet on all the 3 machines.
Till now i am able to access all machines but not the internet. Internet is available only on 1 machine in which i have 2 NIC's. One is from my ISP and other is local lan card.

Can any body suggest my how to bring internet on all the 3 machines.
If IP tables is the solution, then please tell me how to configure those tables.

IP add of my server machine is 192.***.*.1

IP address of my ISP 10.*****
DNS =61.******
Common gateway=10.******

eth0 is my Local lan
eth1 is for internet distribution

in my eth1 i have statically given the IP info of my ISP and in route, i have given all the IP address of 3 machines in the destination Network and given the gateway of my ISP.

In eth0 ie Local Lan, I have given IP address of my machine statically instead of automatically obtain becoz in automatic connection i could activate my eth0.

Now with these settings i am only able to get internet on my machine with 2 NIC's but i can ping all of my 3 machines on the lan
 
Old 07-18-2003, 11:25 AM   #2
mayankjohri
Member
 
Registered: Mar 2002
Location: INDIA
Distribution: Mandrake Linux 9.2, Knoppix 3.0
Posts: 158

Rep: Reputation: 30
did you tried the forward_ipv4=yes
 
Old 07-18-2003, 11:30 AM   #3
varunbihani
Member
 
Registered: Jul 2003
Location: indore, india
Posts: 69

Original Poster
Rep: Reputation: 15
where to do this??

forward_ipv4=yes

in which file and how
 
Old 07-18-2003, 11:39 AM   #4
serz
Member
 
Registered: Apr 2003
Location: Buenos Aires, Argentina
Distribution: Slackware, Gentoo
Posts: 397

Rep: Reputation: 30
I'd suggest you to try MonMotha's IPTABLES firewall. It will do all the job for you.
 
Old 07-18-2003, 11:45 AM   #5
Mathieu
Senior Member
 
Registered: Feb 2001
Location: Montreal, Quebec, Canada
Distribution: RedHat, Fedora, CentOS, SUSE
Posts: 1,403

Rep: Reputation: 46
Actually, forward_ipv4=yes will not work in RedHat.

Edit the file /etc/sysctl.conf and on the line net.ipv4.ip_forward = 0, change 0 to 1.

# Controls IP packet forwarding
net.ipv4.ip_forward = 1


IPtable rules are located in /etc/sysconfig/iptables

First, we need to flush the old rules.
iptables -F INPUT
iptables -F OUTPUT
iptables -F FORWARD
iptables -t nat -F

The following commands will create new rules for your system.
iptables -P INPUT ACCEPT
iptables -P OUTPUT ACCEPT
iptables -P FORWARD DROP

iptables -A FORWARD -i eth1 -o eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT
iptables -A FORWARD -j LOG

iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE

To save iptables modifications, use service iptables save.

Last edited by Mathieu; 07-18-2003 at 11:46 AM.
 
Old 07-19-2003, 12:19 PM   #6
Robert0380
Guru
 
Registered: Apr 2002
Location: Atlanta
Distribution: Gentoo
Posts: 1,280

Rep: Reputation: 47
i dont have that file in redhat (/etc/sysconfig/iptables) i put my my rules in a custom file (firewall.sh) and i put the command:

sh flrewall.sh


in rc.local, did u make taht file (etc/sysconfig/iptables) or is in a different distribution from redhat?

Last edited by Robert0380; 07-19-2003 at 12:20 PM.
 
Old 07-19-2003, 12:46 PM   #7
Mathieu
Senior Member
 
Registered: Feb 2001
Location: Montreal, Quebec, Canada
Distribution: RedHat, Fedora, CentOS, SUSE
Posts: 1,403

Rep: Reputation: 46
By default, the file is NOT created.
If you want to create it, type service iptables save. This will save your rules.

You will no longer need firewall.sh if you edit the file /etc/sysctl.conf and change 0 to 1 on the line net.ipv4.ip_forward = 0.

You will also need to start iptables on boot.
 
Old 07-19-2003, 07:28 PM   #8
fortezza
Member
 
Registered: Mar 2003
Location: Colorado
Distribution: Fedora Core 4
Posts: 297

Rep: Reputation: 30
Same Problem Setting up Linux Router/Firewall

I am having problems with the DSL router ( Cisco 678 ).

What I have done is split my home network up into 2 networks, and insecure one and a securre one. Looking from the Internet, here is the setup I am using while testing the firewall router:

Test setup:
DSL Line->Cisco 678 -> Switch ( 10.0.0.0/24 network ) -> Firewall eth0 -> Firewall eth0 -> test computer eth0 ( network is 10.0.1.0/24 ) .

I have a laptopn on 10.0.1.0/24 and a workstation on 10.0.0.0/24 and they can ping/ssh each other with no problems. The only problem I have, at the moment is the while all the computers on 10.0.0.0/24 network can ping the router and be pinged by it , the lapt and router are not communicating at all. I set up the router to route packets for the 10.0.1.0/24 network the same way I set up the workstation ( which is on the same network as the router ), but it just gives me a timeout. It can ping the firewall/router interface on its local network, but either it isn't using the fw/router to route packets for the 10.0.1.0/24 network, or the fw/router is refusing to route them. The second isn't very likely since it is routing for all of my linux workstations.

To recap , from my workstation I can ping the DSL router, both nic's in the linux FW/Router, and the laptop the is connected to the fw/router. From my DSL router, I can ping all interfaces on its network, but cannot ping the fw/router eth1 ( 10.0.1.0/24) interface nor the laptop on that interface.

Also note that I have turned off all of my DSL routers filters and stopped all IPTables services on the linux machines to simplifiy troubleshooting.


Any ideas? My plan is to have a setup like this:

DSL Line->Cisco 678 -> Firewall eth0( 10.0.0.0/24 network ) -> Firewall eth0( 10.0.1.0/24 network ) -> switch -> all of my computers ( 10.0.1.0/24 ) .

Here are a few routing tables:

laptop ( that pings everything except the DSL router )
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 10.0.1.1 255.255.255.0 UG 0 0 0 eth0
10.0.1.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth0
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default 10.0.1.1 0.0.0.0 UG 0 0 0 eth0

workstation ( same as laptop but it can ping the DSL router )
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 * 255.255.255.0 U 0 0 0 eth0
10.0.1.0 10.0.0.2 255.255.255.0 UG 0 0 0 eth0
192.168.0.0 10.0.0.2 255.255.255.0 UG 0 0 0 eth0
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default 10.0.0.1 0.0.0.0 UG 0 0 0 eth0

DSL Router
[TARGET] [MASK] [GATEWAY] [M][P] [TYPE] [IF] [AGE]
0.0.0.0 0.0.0.0 0.0.0.0 1 SA WAN0-0 0
10.0.0.0 255.255.255.0 0.0.0.0 1 LA ETH0 0
10.0.1.0 255.255.255.0 10.0.0.2 2 SAR ETH0 0
66.0.0.0 255.0.0.0 0.0.0.0 1 A WAN0-0 0

FirewallDestination Gateway Genmask Flags Metric Ref Use Iface
10.0.0.0 * 255.255.255.0 U 0 0 0 eth0
10.0.1.0 * 255.255.255.0 U 0 0 0 eth1
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default 10.0.0.1 0.0.0.0 UG 0 0 0 eth0
 
Old 07-19-2003, 07:33 PM   #9
RKris
Member
 
Registered: May 2002
Location: UK
Distribution: Mandriva linux
Posts: 152

Rep: Reputation: 15
Man!! you need to buy a book on Cisco routers or on RedHat , rather than dumping your head in here.

regards
Krishna
 
Old 07-19-2003, 10:51 PM   #10
fortezza
Member
 
Registered: Mar 2003
Location: Colorado
Distribution: Fedora Core 4
Posts: 297

Rep: Reputation: 30
Work-around - transparent bridging

For now I am going with a workaround that I found - transparent bridging.

So what I did it made the firewall system transparent to my network, it copies everything in between the two interfaces, and filters the packets as they pass through. It doens't even need an IP address!

First install the bridge utilies found here ->
http://bridge.sourceforge.net/download.html

Then follow the instructions here ->
http://www.linuxquestions.org/questi...451#post188451

After you are done, you will only have access to the firewall from the keyboard/mouse connected to it, but it can be dangerous to try and remotely configure firewall rules anyhow ( you could disconnect yourself accidently and not get back in! ). One note is that older kernels ( older than 2.4-18, I presume ) did not have bridging capability enabled by default, but the kernel that came with Mandrake 9.1 did, so all I needed to install were the bridging tools referenced above.

I read somewhere that the downside of transparent bridging is you can only process incoming packets and not outgoing ones. I will put that to the test in a bit .

I hope this information helps someone else.
 
Old 07-20-2003, 09:34 AM   #11
win32sux
Guru
 
Registered: Jul 2003
Location: Los Angeles
Distribution: Ubuntu
Posts: 9,870

Rep: Reputation: 371Reputation: 371Reputation: 371Reputation: 371
you could use shorewall to share your internet connection and protect your local area network... it makes iptables easy...

http://www.shorewall.net/

here's the guide for a two-interface setup like the one you described:

http://www.shorewall.net/two-interface.htm

you might also want to use something like squid to speed things up a little for the surfers and save bandwidth:

http://www.squid-cache.org/
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Internet connection sharing between 2 slackware machines Random`Zero Linux - Networking 6 01-03-2005 11:22 PM
Internet Connection Sharing 2 FC1 machines explorer Fedora 1 05-05-2004 02:09 AM
Sharing Internet with two machines, ping doen't work sandrain Linux - Networking 7 02-24-2004 12:59 PM
File sharing between two linux machines sridharanvinod Linux - Distributions 2 02-01-2004 11:23 AM
Sharing drives - 2 Linux Machines mjgeiger Linux - Networking 4 10-25-2002 11:37 PM


All times are GMT -5. The time now is 07:40 AM.

Main Menu
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration