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[nos-bbs] Fwd: Re: Routers and NAT oops

George [ham] VerDuin k8rra at ameritech.net
Mon Mar 1 17:19:31 UTC 2010

Kerry -- I blew the NAT thing -- sorry for the misinfo.

-------- Original Message --------
Subject: 	Re: [nos-bbs] Routers and NAT
Date: 	Mon, 01 Mar 2010 08:53:27 -0500
From: 	George [ham] VerDuin <k8rra at ameritech.net>
To: 	TAPR xNOS Mailing List <nos-bbs at tapr.org>

Good morning Kerry.
Barrys suggestion is encouraging.

On 02/28/2010 09:50 PM, Kerry Smith wrote:
>  What i'm seeing in the Linksys is this...
>  I Test a telnet connection into the Nos box.  On the ETH0 trace, I
>  see the packet come in from the external NON 44 IP to the Internal
>  box IP, such as -- source Dest
If the source for this packet is outside the LAN, then Linksys should
have done NAT as part of the DMZ mapping.
If your LAN is class C, then IP is not OK for a Linksys
gateway IP.
Jnos doesn't have a good request packet to respond to.

>>>>>  Perhaps wrong -- jnos*may not*  have a good packet to respond to.

Compare the following successful encap exchange over tun0 interface:
Sat Feb 13 12:44:41 2010 - tun0 recv:
IP: len 64> ihl 20 ttl 210 prot IP
IP: len 44> ihl 20 ttl 224 prot TCP
TCP: 3600->1024 Seq x2ee1f000 Ack x572c001 ACK SYN Wnd 2048 MSS 512

Sat Feb 13 12:44:41 2010 - tun0 sent:
IP: len 60> ihl 20 ttl 224 prot IP
IP: len 40> ihl 20 ttl 224 prot TCP
TCP: 1024->3600 Seq x572c001 Ack x2ee1f001 ACK Wnd 2048

Specifically see that NAT does not map the source IP, only the 
destination IP.
My mistake to expect the gateway IP as the source IP.
The remainder of my comments stand.

If we trade more data, I invite you to use my direct addr off the 
Sorry for the mis-step.

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