[CentOS] Optimizing CentOS for gigabit firewall

sadas sadas mailrc at abv.bg
Fri Dec 18 19:36:57 UTC 2009

 I will explain more deeply. I need to deploy a firewall(s) in front of web server farm because I need to do billing - I will use CentOS with iptables + ipset to store a list if my clients so when client doesn't pay his server's IP is out of the list and he can't access the web server.

Second - I know that iptables is very heavy and it's not recommended to use it in gigabit firewall but I don't have a choice as far as I know only ipset works with iptables. I don't know can pf store 500 IPs in one list. Ipset is written for that purpose. 

I can't find information is there linux or BSD distribution with effective firewall that uses optimized algorithm to store hundreds of IPs and to forward huge traffic. Any idea?


  I'll second damn near everything nate said, and hopefully add a tidbit or two.

If you're new to BSD, you may want to consider the pfsense project in the aforementioned active-active configuration.

It gives you a nice, intuitive gui to manage your failover firewalls, if you insist on putting a firewall in front of your web servers.

Better to secure the box, leave only the ports you need open on the public interfaces, and don't firewall them.

Also, I'd strongly consider running your firewalls with no disk at all.
 A Live CD, CF card or USB Flash to boot off of, remote syslog and
one less subsystem (disks) to buy/fail makes for some mighty cheap 1U servers.
 A single dual-core with core speeds above 3.0Ghz
and 4GB of RAM is to pass Gb @ line rate - ethernet overhead.
 Truth be told, it's already being done on much less
than that.
 You can also load balance your traffic, albiet somewhat primitively with it.
 If you really want massive throughput, consider toying
around with extremely expensive 10G gear, size RAM appropriately, and see how PF performs under multi-processor, high-core speed.
but if you're handling over a Gb of traffic and you can't split the application into multiple farms, that's the best move.

Akamai, for instance, runs 10G to each rack, each rack has around 20-24 servers, and they run GB to the server.

 pfsense.org  has extensive information about hardware requirements, features, and what you're looking to do.

 https://calomel.org/network_performance.html  is an excellent BSD firewall performance site.

One thing to note, you are claiming to want to deploy this as a passive bridge.
 You cannot do what you want to do
running anything in bridge mode.
 The packets need to route somehow.
 Get a /29 from your colo provider and ask
to have your existing block routed through it once you've tested it.

Another option for a seamless failover, is to alias a different range of IP's to the server interfaces, put a /29 and whatever
netblock you want to end up being your public IP block on the PFSense hardware.
 When you're convinced everything's
working through rigorous testing, put a test domain up pointing to that block, modify virtualhost entries on the servers to
respond to that domain with your production web site, and test some more.
 Once you're convinced that's working perfectly,
make the changes in DNS to point your production domain at the IP's you want, and failover will happen with DNS convergence.


 On Fri, Dec 18, 2009 at 9:06 AM, nate   centos at linuxpowered.net >  wrote:
     sadas sadas wrote:
> Hi,
I want to configure CentOS on powerful server with gigabit
> adapters as transparent bridge and deploy it in front of server farm.
> Can you tell how to optimize the OS for hight packet processing? What
> configurations I need to do to achieve very hight speeds and thousands of

  iptables makes a TERRIBLE firewall, use pf instead


Also consider how your going to provide redundancy, if you have a web
server farm you want to protect them with at least two firewalls, not


I haven't used CARP myself but did setup a pair of pf firewalls about
5 years ago in a large network in bridging mode, the layer 3 fault
tolerance was provided by OSPF on the core switches, the firewalls
were active-active(with pfsync) since they were layer 2 only.

Maybe someday linux will fix the overly complex iptables system to
something that is more manageable, not holding my breath though.

If you want really high speed(say multi GbE) though you'll want/need
to go with an appliance based solution.

Also since your referring to a web server farm, it is perfectly
acceptable to not use firewalls these days, if you have a good
load balancer that serves the same role as a firewall in that it
only passes traffic that you specifically configure it to pass. Also
in high traffic environments the performance of load balancers
destroys most firewalls, making investing in a high end firewall
a very expensive proposition.

I've worked for the better part of the last 10 years with
companies who did not have firewalls in front of their web servers
for this reason, it didn't make sense $ wise, because the benefit
wasn't there, and the added complexity, and performance implications
wasn't worth it either. Talk to most load balancing companies and
they'll tell you this themselves.
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