[CentOS] Optimizing CentOS for gigabit firewall

Peter Serwe peter.serwe at gmail.com
Fri Dec 18 21:05:23 UTC 2009


I don't know jack about IPSet, but I know enabling or disabling hosts in
bare stock PF without the gui in front of it is about as easy as it gets.

The PF configuration file syntax was designed from the ground up to be sane,
unlike iptables, which typically needs some decent sysadmin scripting or
using fwbuilder to make any good sense of.  There is no finer opensource
firewall product on the market, in terms of performance, ease of
configuration and use, and other issues.

If you're not opposed to vi, for what you're looking to accomplish, moving
to BSD and pf is a no-brainer.  PF can definitely handle a list of 500 hosts
and anything else you've mentioned.  It's absolutely capable, easier, and in
general, for anything that involves packet filtering at all, about as good
as it gets.

Peter

On Fri, Dec 18, 2009 at 11:36 AM, sadas sadas <mailrc at abv.bg> wrote:

> 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?
>
> regards
>
>
>
>
>
>
>
> 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.
>
> Peter
>
>
> 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
http://truthlightway.blogspot.com/
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