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Network Security Pen-Test
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Re: VPN protocols

Subject: Re: VPN protocols
Date: Wed, 22 Dec 2004 10:48:57 -0700
On Wed, 22 Dec 2004 09:04:16 -0800, John Forristel (SunGard-Chico)
<John.Forristel@sungardbi-tech.com> wrote:
GRE and ESP are protocols, not ports, so they are transported through on
configured ports.  In Cisco, you permit gre and esp through for the VPN
traffic.

No, they are not transported on configured ports. They are transported
via IP, and your IP stack is informed of this by the 10th byte of the
IP header. In tcpdump parlance:

(ip[9] = 47) GRE
(ip[9] = 50) ESP

-- 
GDB has a 'break' feature; why doesn't it have 'fix' too?

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