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Linux Question - 2 Network Cards

Posted on 2004-08-23
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Last Modified: 2013-11-09
I'm going to rebuild my Linux machine.  At the moment with the current set up I have only one network card, connected to the rest of my network and an adsl modem through the one switch.  As there any specific advantage to having two network cards in a computer?

Regards

Ash
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Question by:mortar
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by:MarkDozier
ID: 11877418
Good question. And the answer is Yes and No.
It really depends of the prupose of the box.
If it is a router then 2 NICS are a benifit.
If this is an IPTABLES filrewall then two NICs are a benifit
If this is a IDS device 2 nics are benifit

If this is a workstation attached to a swit ch 1 nic is sufficent in most cases

Again it all depepnd on the purpose of the box.
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by:master_chris
ID: 11877653
Single Network Card

Linux Box default gateway is the ADSL modem/router. I will also assume that all other workstations will have the default gateway set to the ADSL modem/router also.

Two Network Cards

1 Network card runs to the Switch
1 Network card runs direct to the ADSL Router.
Benefits are that no workstation is in direct contact with the ADSL/Modem Router.   Workstations Route through the Linux Box to the ADSL/Router.
 Now you have the option of playing with your IPTABLES/IPCHAINS (Linux Firewall). You can set port forwards such as HTTP, DNS, SSH, TELNET etc.

So in summary option 2 has alot more security benefit. You are reliant on the Linux Box to access the internet. Again this really depends on your purposes of your Linux Box.




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by:marcin79
ID: 11878795
I thinh that if You have a free network card You may safely install it in linux box. If You will not use it, You can - simply - not install drivers for it - or keep it in down state (i rather preffer the second solution), but in a future when You want to either experiment or use your linux box for some of tasks mentioneg above it will be much faster then installing the card from the beginning.
For me You shold install it just to have some test environment.

Hope this helps
Regards
Marcin
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by:mortar
ID: 11878838
I already have IP Chains, and port forwarding options set up on the current configuration.. So basically the only real advantage is that you can seperate the ADSL modem from the clients?  I just wondered if it was better for network throughput, reduced packet loss or network errors or anything like that because it's seems a waste to have two network cards, one basically reserved for the ADSL modem when you can basically perform the job with one less card and run the ADSL modem back to the switch with a crossed cat5 cable.
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master_chris earned 50 total points
ID: 11879009
Yes it is better network throughput. This is the Champion way to set up a ADSL connection on a  linux box. It will reduce traffic on your HUB/SWITCH..  and seperates the ADSL modem from clients.

Also if you have the adsl modem  network card on a completely difference range, for example 10.0.0.X.  where as you could have your network on 192.168.1.X.  

What i am more interested in is Squid tuning. I want to throttle tune :)

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by:marcin79
ID: 11879606
additionally if You will run linux as a router You can use some kind of shaper. I've seen magic when that kind of configuration was running in connection with wondershaper (HTB)
wondershaper home: http://lartc.org/wondershaper/
HTB home (see performance analysys): http://luxik.cdi.cz/~devik/qos/htb/

Additionaly You can configure it to act as a speed limiter for various users

Regards
Marcin
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by:master_chris
ID: 11887859
Also one of the benifits i missed is you can run the ADSL modem in PPPOE mode and set up eth interfaces with external ip's. If you have more than 1 ip address you can set up several interfaces. and you can do what you like with these extra ips.
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