Re: Risks of patched servers behind de-randomizing NAT
OT, I agree, but certainly relevant to the issue at hand.
I noticed the same thing a couple of weeks ago after I upgraded to
9.4.2-P1. It is absolutely the PIX and will happen with 6.x through 8.x
However, this issue is related to how the code PATs outbound traffic and
can be resolved by setting up a static NAT for the nameserver.
You can do this on the fly by adding (adjusting for actual interface
static (inside,outside) ...
clear xlate local <IP addr>
clear xlate global <IP addr>
At that point the various DNS tests mentioned on the list should report
Of course, all this assumes you are being routed enough public IP
address space and have a free address to use...
On Fri, 2008-08-01 at 06:43 -0500, Kirk wrote:[color=blue]
> Mark Andrews wrote:[color=green][color=darkred]
> >> David Carmean pisze:
> >>> I seem to have lost a message where somebody from ISC (Paul?) was going to
> >>> release an updated/new advisory regarding the source-port de-randomizing
> >>> effects of many NAT implementations will have upon patched servers.
> >> But why someone puts a DNS server behind a NAT? It's a bit nonsensical...[/color]
> > There are lots of reasons to put a recursive server behind
> > a NAT. It's something that just "should work" and does if
> > you arn't trying to introduce entroy by randomising ports.
> > Note. Not all NATs have bad behaviours in this respect. Some try
> > to preserve the internal port.
> > MArk
> This is slightly off topic. However, I thought it appropriate to share.
> At home I have two recursive servers sitting on a private lan behind a
> Cisco PIX 501. These servers are mostly to play with, but also provides
> recursion to all the nodes in my house.
> After upgrading these servers to the latest patched version of BIND, I
> tried the porttest query to test randomization. Well, both got POOR
> ratings. This led me to believe that my PIX was the culprit.
> Last night, I spent close to 30 with the Cisco help desk trying to get
> assistance, only to find that because my unit was out of warranty and I
> had no contract, they could be of no help. They suggested I open a
> "web-help" ticket with Cisco. This also returned no help for the same
> reason. Also, my appliance is already at the highest code OS leve.
> I guess those of us who purchased Cisco products that are out of
> warranty and under no contract are at risk until we purchase some new
> Sorry for the rant, but it "seemed" sort of appropriate here in this thread.
> - Kirk