[Full-Disclosure] MSN\Qwest ships DSL modem with "unconfigurable" firewall

[Volker Tanger]

Greetings!

On Fri, 2 Apr 2004 10:19:59 -0700 James Lay <jlay at ameriben.com> wrote:

> Real quick...just implemented a Cisco VPN concentrator here and lo and
> behold certain users couldn't get in.  The concentrator is setup with
> the standard UDP port 500.  All users BESIDES MSN\Qwest DSL users
> could get right on.  After a few calls and some frustration, Qwest
> informed us that the firewall on the DSL router they ship is
> "unconfigurable"


That is because you'll need AH/ESP (== IP type 50/51) in addition to
IKE, if you want to implement IPSec VPN.

Most el-cheapo routers only support 
	ICMP (== IP type 1)
	TCP  (== IP type 6) 
and 	UDP  (== IP type 17)

Thus you'd need an encapsulation of ESP traffic like the soft-VPN
clients of Nortel and CheckPoint offer (probably just because of this
problem). Or you'd have to have a router that really supports 
"IPSec-Forwarding" (i.e. blind forwarding of IP types 50+51 to a
specific IP to be configured in the router). Data sheets don't always
tell the truth here, so you really should verify before rollout...  

Qapla'

Volker Tanger
ITK Security