[CentOS] Optimizing CentOS for gigabit firewall

Peter Serwe peter.serwe at gmail.com
Fri Dec 18 18:21:20 UTC 2009

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

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
> >  packets?
> iptables makes a TERRIBLE firewall, use pf instead
> http://www.openbsd.org/faq/pf/index.html
> 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
> one.
> http://www.openbsd.org/faq/pf/carp.html
> 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.
> nate
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Peter Serwe
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