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Re: [lwip-users] forwarding and NAT

From: Marleen Vos
Subject: Re: [lwip-users] forwarding and NAT
Date: Wed, 04 Feb 2015 16:19:39 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0


Thank you for the quick response.

Now I know NAT is out of the question, I could put my question in another way:

The situation I have in mind is to use an embedded device as a router, with ethernet on one end, and serial on the other end (connected to GPRS). There can be multiple devices connecting over the ethernet link, so the forwarding would actually need to be able to work in this situation too.

A connection coming in over the serial link would need port forwarding to reach the correct address behind the router. Is that possible with lwip?

Devices making a connection from the ethernet side, have to be forwarded to the serial side. Will this forwarding work for multiple devices without (stateful)NAT? I would think not, but I'm not sure on this.

Thanks again for your time,

On 4/02/2015 15:33, Sylvain Rochet wrote:

On Wed, Feb 04, 2015 at 01:48:51PM +0100, Marleen Vos wrote:

I was looking around to see if lwip supports forwarding from PPP
(serial) to Ethernet (in both directions),

Yes, it works in the master branch.

and if NAT was possible.

lwIP does not have NAT support, there was a task about it but it didn't
materialise. NAT is quite hard to do correctly, require huge amount of
memory (I guess you are actually talking about stateful NAT), and in my
opinion this is outside the scope of a small IP stack. If you need NAT
or forwarding I am personally suggesting using Linux on ARM or MIPS SoC,
Linux have a more-than-comprehensive NAT support with NAT helpers for
many hard-to-deal-with protocols.

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Thanks, but I don't care.


Marleen Vos
Embedded Software Engineer
Bausch Datacom NV
Tiensesteenweg 54-56
B-3360 Korbeek-Lo
tel. +32 16 461288
fax. +32 16 463151

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2015.0.5646 / Virus Database: 4281/9056 - Release Date: 02/04/15

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