cancel
Showing results for 
Search instead for 
Did you mean: 

NO NAT Service

JonnyF
Grafter
Posts: 206
Registered: 02-08-2007

NO NAT Service

Hi,

Hope one of you can help, since Plusnet support can't!?

I have a "NO NAT" IP range from Plusnet

x.x.x.72/29 ( which gives me 8 IP's of which 6 are usable .73 to .78 )

I have a Linksys WAG354G with NAT disabled and my PC's in the above range (.73 is the router IP).

Almost everything works great, and all IP's are contactable directly from the Internet as designed.

However, for some reason, there are several websites that are uncontactable. For example, www.microsoft.com, www.msn.co.uk, www.grc.com
All other websites tested work just fine!

ALL sites are contactable if I use standard NAT routing.

Anyone had a similar issue or can shed some light on this issue?

Thanks in advance,

Jon.
4 REPLIES
N/A

NO NAT Service

Is your router providing DNS? Can you ping the sites in question?
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

NO NAT Service

Hi,

Have you tried eBay? MSN/Microsoft and eBay tend to crop up together (I think Amazon is another). The cause usually seems to be MTU/RWIN related.

Try changing the MTU to 1430 and MTU to 57600 (if you have 2Mbps, 13900 if you have 512 or 27800 for 1Mbps). Reboot your PC and retry the sites.

It's a little puzzling though if it works in NAT, but changing the MTU is worth a try and if it doesn't work from there we can think of something else.
JonnyF
Grafter
Posts: 206
Registered: 02-08-2007

NO NAT Service

Hey Presto! Thanks very much for the info! Its alive!

Well, setting the MTU on the router to 1430 (which I had already tried) had no effect by itself.

However, setting the MTU and TCP Receive window to 1430/57600 with DRTCP seemed to do the trick. Although I’m not too sure if the MTU value alone would have been enough? I presume the TCP receive window was set correctly, please can you let me know?

EDIT : A pleasant side effect from changing these values is a marked improvement in speedtest scores! Good news all round!

Thanks again,

Jon.
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

NO NAT Service

This is one of those problems that crops up quite often. I've never really worked out whether it's just one of MTU or RWIN or whether it's the combination of the two. Just seems to work when you tweak both.