nanog mailing list archives

Re: Dynamic routing on firewalls.


From: Valdis.Kletnieks () vt edu
Date: Mon, 09 Feb 2015 10:25:45 -0500

On Mon, 09 Feb 2015 12:56:37 -0200, Patrick Tracanelli said:
On 09/02/2015, at 12:14, Valdis.Kletnieks () vt edu wrote:
On Mon, 09 Feb 2015 11:54:04 -0200, Patrick Tracanelli said:
On a bridged firewall you can have the behavior you want, whatever it is. Passing packets with firewall is down, 
but the box still up.

Owen's point is that passing packets if the firewall is down is really poor
security-wise.   If you run in that configuration, I simply DoS your firewall
(probably from one set of IP addresses), and then once it has fallen over and
is being bypassed, I send my *real* malicious traffic from some other IP
address, totally uninspected and unhindered.  Much hilarity, hijinks, and
pwnage ensues.

Hello Valdis,

If this is really the point, I don’t know what system you are talking about

The one *you* mentioned - "passing packets with firewall is down".  Owen
was pointing out that is a silly configuration:

On 08/02/2015, at 22:48, Owen DeLong <owen () delong com> wrote:
Technically true, but bridged firewalls are pretty much passe these days in the
real world. As a general rule, when the firewall is shut down, one usually
doesn’t want the packets flowing past un-hindered. The fact that this is kind
of the default of what happens with bridged firewalls is just one of the many
reasons hardly anyone still uses such a thing.

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