[CentOS] Multiple WAN link -- CentOS Suitability

John R Pierce pierce at hogranch.com
Thu Jul 19 06:35:28 UTC 2007

Raymond M. Subasic wrote:
> My situation:
> I have a cable modem (COMCAST 6Mbit d/l) and am about to also have DSL 
> (Verizon 3 Mbit d/l). I was thinking of using CentOS (4.4, 4.5, or 
> 5??) as a router/dhcp server/firewall for my home network consisting 
> of 3 to 6 computers at any given time. I seek the wisdom of the 
> members of this list on the following issues:
> -- Is CENTOS a good direction to go? I do not mind manually 
> configuring things or installing lots of packages, and am doing this 
> as both a learning experience for myself and proof of concept for a 
> customer.

Its reasonable. not optimized particularlly as a firewall/routing 
system, its more of a general purpose server but its certainly capable 
of doing firewalling

> -- Is it possible/hard/easy/trivial to share the load between the two 
> connections? Have either link fail and things still work correctly?

possible? yes. hard, definately. easy/trivial, nope. reliably detecting 
a 'failed' link is also tricky as most failures will be upstream from 
you. routing outbound traffic and load balancing two seperate ISPs is 
also tricky.

> -- I plan to build a box for this job – looking for general 
> recommendations of how much horsepower (mem/disk space, etc) is required

a router/firewall can run off a 512MB flashcard, and a 450MHz CPU with 
256MB ram is way more than adequate.

> -- What are the implications of two pipes for incoming connections 
> such as DynDNS based remote desktop or VNC, or web server, FTP, etc

the two connections have two differnet IPs on different networks. you'll 
need to run two DynDNS clients and sort all that out, you'll have two 
seperate possible hostnames to connect to from outside.

webserver, ftp server, etc would typically serve the content to either IP.

> The basic hardware layout I see is 3 nics, 1 GB RAM, 60 GB disk space. 
> 1 NIC for each WAN port, 1 NIC for my local net, some recent CPU.
> I have been browsing through the “Linux Advanced Routing & Traffic 
> Control HOWTO,” but am still not on top of how to get done what I’m 
> looking for. I understand that there are probably products that I 
> could buy to do this, but my preference is to do it myself.

thats the document you need to understand, along with the rest of the 
stuff on http://netfilter.org

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