Voyager 2100/2100/2091 users - please test

[#1]

Thanks to everyone for their comments so far

@ MickKi
>> Perhaps you need to sniff packets before and after the router to see what is being dropped?
Using ethereal on the PC
First arrse
217.146.105.5 -> 192.168.7.2 -> TCP -> http > 1110 []Seq=`769441889 Ack=1 Win-20498 bogus TCP header length (0, must be at least 20).
then kitz leisure
213.171.219.239 -> 192.168.7.2 -> TCP -> http > 1128 []Seq=2712714331 Ack=1 Win-20498 bogus TCP header length (0, must be at least 20).

[#2]

Quote from: kitz

Remote server responds for kitzleisure but not for arrse when doing a tracert  - which is why I find it strange that I cant get http responses via any browser (IE, FF + Opera)

OK, the arrse server implementation (or its firewall) could well be broken on account of not accepting "fragmentation needed" ICMPs (ICMP type 3, subtype 4) packets and therefore never finding out what size packets to return to your machine.  You will probably appear to that server as if you're opening a connection and never respond for the server to send you the website packets through.  Hmm, not clever.
The kitzleisure is running on MSWindows, it has p*ss-poor web code on its pages, so it is anyone's guess what's broken there.

Quote from: kitz

MTU 1430 should be fine

Hmm, it might not!  Try setting your MTU (on your computer) as 576 bytes only.  Leave the router where you have it, or even increase it to 1500.
If that works start increasing it until it stops.  You may also want to run Wireshark to see if packets sent from your PC are responded to by the server.
<rant> I suspect that after all this it may be easier to contact the owners of these websites and ask them to get their act together.  The Windows box because it shouldn't even be allowed on line and the arrse because they are so paranoid about security (at least that's what the CMS tool website says) that they have probably broken the server implementation to achieve it.  </rant>
HTH.
--
Regards,
Mick

[#3]

I should have given the firmware version before - rather than just 'not changed it'.
It is 2.14.02.06_a023g1

[#4]

FWIW:  BT voyager 2091, plusnet customer for 2 months, no problem with either web site.

[#5]

Quote from: kitz

Thanks to everyone for their comments so far @ MickKi >> Perhaps you need to sniff packets before and after the router to see what is being dropped? Using ethereal on the PC First arrse 217.146.105.5 -> 192.168.7.2 -> TCP -> http > 1110 []Seq=`769441889 Ack=1 Win-20498 bogus TCP header length (0, must be at least 20). then kitz leisure 213.171.219.239 -> 192.168.7.2 -> TCP -> http > 1128 []Seq=2712714331 Ack=1 Win-20498 bogus TCP header length (0, must be at least 20).

I'm no network guru, but both cases seem to suffer from the same problem.  INVALID packets.  The headers in question may not have been sent with 0 length from the originating servers.  They may have been 'modified' on their way as the packets traverse SPI firewalls.  I am not sure why this happens.  Someone who studied this subject may be able to comment more intelligently.  It may well have something to do with PMTUD malfunctioning on these servers.
What do you get when you swap the router?
--
Regards,
Mick

[#6]

So Im sending out SYN requests OK.... data packets appear to be coming back to the router OK.. but theres a problem with the TCP header... possibly going wrong on the LAN side since data appears to have arrived at the router OK... so the header must be OK up to hitting the router.
By default the V2100 is set at MTU of 1400.
I'd already increased this to 1430 both on the WAN and LAN side in line with what is set on the PC.

Quote

But we have set it to an MTU of 1500, having had trouble with Macromedia/Adobe sites not loading when set to the factory default of 1400.

Even though I dont have any probs with Macromedia/Adobe and even though theres no data framentation at 1430 as per the check in my post above. - I thought theres no harm in at least trying DTEGs suggestion

So I change MTU to 1500 on the LAN side settings -
Then had a heart attack because the router appeared to die and wouldnt resync at all!!

So I turned off the router and left it completely switched off for a while
Switches router back on - Router syncs back up.

Voila!
Everything works ok - Big thank you to everyone thats replied.

---------------------

Sorry for my delay in reply - but that was mostly due to the time period when I thought my router had given up the ghost completely... and I hadnt yet seen MickKis reply at 18:30
I think I will leave it at MTU 1500 on the LAN side... changing this setting forces the router to go into reboot and reset mode from which it didnt appear to recover too well at first.
Touch wood it now seems fine.

[#7]

Quote

I'm no network guru, but both cases seem to suffer from the same problem.  INVALID packets.  The headers in question may not have been sent with 0 length from the originating servers.  They may have been 'modified' on their way as the packets traverse SPI firewalls.  I am not sure why this happens.  Someone who studied this subject may be able to comment more intelligently.

Further to this - I would appreciate any comments if anyone does know any more info about this.
Particularly this bit "They may have been 'modified' on their way as the packets traverse SPI firewalls."

[#8]

I have had my MTU set to 1500 since shortly after I bought the 2100 - several years ago - so that may tie up.