problem - maybe due to 3Com Wireless DSL router?

Hello

Question: Why does one of my PCs load web pages flawlessly whereas the other
one, all of a sudden, doesn't?

Background: My router, via NAT, serves two computers. The two computers run
Windows XP and connect via Wi-Fi to the router. The router serves out IP
addresses to the two computers via DHCP. The firewall in the router is
enables and it stops ICMP amongst other things.

The router is a 3Com officeconnect and, up until a couple of days ago when I
installed Mozilla thunderbird, all was well.

Now, however, all is not well. Dowstairs PC continues to work flawlessly as
ever. Upstairs PC will sometimes load webpages, sometimes will refuse to
load the same webpage, or will partially load a page minus the images. This
is the case with the 3Com's firewll enabled.

If I disable the router firewall, the downstairs PC continues to work
flawleslly and now, so does the upstairs PC.

On the upstairs PC, disabling Windows firewall and also Zonealarm and
confirming that no ZA services are running results in the same situation as
having the whole lot running - web pages load properly if teh router
firewall is "off", and don't load properly if the router firewall is "on".

(For reference, the downstairs PC has the Windows Firewall enabled, but no
other firewall software).

So, having checked the router firewall rules, there isn't anything that I
can see singles out the upstairs from the downstairs PC.


I've uninstalled Thunderbird - I think that the installation being
cnincident withthese problems is a red herring but I'm not an expert - and
the upstairs PC still fails to load web pages correctly.

The problem persists in IE7 and in firefox - I have checked the settings in
both, disabled add-ons i firefox, done a variety of tests and can't ID the
cause of the problem. No malware that I can find (spybot S&D, WMSRT,SAS),
all my IPCONFIG settings look right, I can ping anything from either
machine...

Can anyone suggest where I might need to look please?

DDS

In an earlier contribution to this discussion,
Duncan Di Saudelli <(E-Mail Removed)> wrote:

> Hello
>
> Question: Why does one of my PCs load web pages flawlessly whereas
> the other one, all of a sudden, doesn't?
>
> Background: My router, via NAT, serves two computers. The two
> computers run Windows XP and connect via Wi-Fi to the router. The
> router serves out IP addresses to the two computers via DHCP. The
> firewall in the router is enables and it stops ICMP amongst other
> things.
> The router is a 3Com officeconnect and, up until a couple of days ago
> when I installed Mozilla thunderbird, all was well.
>
> Now, however, all is not well. Dowstairs PC continues to work
> flawlessly as ever. Upstairs PC will sometimes load webpages,
> sometimes will refuse to load the same webpage, or will partially
> load a page minus the images. This is the case with the 3Com's
> firewll enabled.
> If I disable the router firewall, the downstairs PC continues to work
> flawleslly and now, so does the upstairs PC.
>
> On the upstairs PC, disabling Windows firewall and also Zonealarm and
> confirming that no ZA services are running results in the same
> situation as having the whole lot running - web pages load properly
> if teh router firewall is "off", and don't load properly if the
> router firewall is "on".
> (For reference, the downstairs PC has the Windows Firewall enabled,
> but no other firewall software).
>
> So, having checked the router firewall rules, there isn't anything
> that I can see singles out the upstairs from the downstairs PC.
>
>
> I've uninstalled Thunderbird - I think that the installation being
> cnincident withthese problems is a red herring but I'm not an expert
> - and the upstairs PC still fails to load web pages correctly.
>
> The problem persists in IE7 and in firefox - I have checked the
> settings in both, disabled add-ons i firefox, done a variety of tests
> and can't ID the cause of the problem. No malware that I can find
> (spybot S&D, WMSRT,SAS), all my IPCONFIG settings look right, I can
> ping anything from either machine...
>
> Can anyone suggest where I might need to look please?
>
> DDS


It's a mystery! I don't know the answer - but if you find it, please let me
know because I've got more or less the same problem.

We have 2 PCs, both running Win XP SP2, and both hard wired to the same sort
of 3Com router as yours. Some while ago - maybe a couple of years - my spam
screening program (Mailwasher) plus my Outlook email client suddenly stopped
working on my PC. The only way I could get them to work was to turn off the
router's firewall - and it has remained off ever since.

I've just turned it on again and - with it on - Mailwasher etc. no longer
work, just as before. *However*, I've just tried Mailwasher on my wife's
computer while the firewall was on and - blow me - it works ok! So I presume
that there must be some subtle difference somewhere in the network settings
between our two computers, but I've no idea what. I wonder if there's a clue
in your reference to Firebird? I run Mozilla Firefox as my default browser,
whereas my wife only uses IE, and Firefox isn't installed on her PC.
--
Cheers,
Roger
______
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Roger
>> Question: Why does one of my PCs load web pages flawlessly whereas
>> the other one, all of a sudden, doesn't?

....<snip>...

> It's a mystery! I don't know the answer - but if you find it, please let
> me know because I've got more or less the same problem...<snip>...I wonder
> if there's a clue in your reference to Firebird? I run Mozilla Firefox as
> my default browser, whereas my wife only uses IE, and Firefox isn't
> installed on her PC.

I seem to have fixed the problem on the "upstairs" PC - but the method seems
unlikely to be related to the cause. I deleted the Firefox profile, started
Firefox isn safe mode and returned it to its normal startup basic settings,
created another profile and now it seems to be working normally!

Might it be worth you doing an experiment - install IE on your "broken" PC
and install FF on your wifes'? Then see if the problem moves with the
browser perhaps ...

I tried restoring the 3Com settings to a known earlier configuration from a
few months ago, by the way (frgot to mention it in my earlier post) - that
made no difference to my problem.

My vague guess (bearing in mind I don't know a fat lot about any of this )
is the the XP "hosts" file is addressed differently in some way and maybe it
relates to the NAT lookup table in the router or something . It's all a bit
beyond me. (My machines are both XPSP3, up-to-date, by the way).

I'm about to reboot (again) and do some more tests. If the situation remains
fixed then that's that! But if I run into further problems i.e. the "delete
FF profile" approach turns out NOT to be a fix, I'll report back.

let us know how you get on, should you decide to try different browsers in
different machines.


DDS

In an earlier contribution to this discussion,
Duncan Di Saudelli <(E-Mail Removed)> wrote:

> Roger
>>> Question: Why does one of my PCs load web pages flawlessly whereas
>>> the other one, all of a sudden, doesn't?
>
> ...<snip>...
>
>> It's a mystery! I don't know the answer - but if you find it, please
>> let me know because I've got more or less the same
>> problem...<snip>...I wonder if there's a clue in your reference to
>> Firebird? I run Mozilla Firefox as my default browser, whereas my
>> wife only uses IE, and Firefox isn't installed on her PC.
>
> I seem to have fixed the problem on the "upstairs" PC - but the
> method seems unlikely to be related to the cause. I deleted the
> Firefox profile, started Firefox isn safe mode and returned it to its
> normal startup basic settings, created another profile and now it
> seems to be working normally!
> Might it be worth you doing an experiment - install IE on your
> "broken" PC and install FF on your wifes'? Then see if the problem
> moves with the browser perhaps ...
>
> I tried restoring the 3Com settings to a known earlier configuration
> from a few months ago, by the way (frgot to mention it in my earlier
> post) - that made no difference to my problem.
>
> My vague guess (bearing in mind I don't know a fat lot about any of
> this ) is the the XP "hosts" file is addressed differently in some
> way and maybe it relates to the NAT lookup table in the router or
> something . It's all a bit beyond me. (My machines are both XPSP3,
> up-to-date, by the way).
> I'm about to reboot (again) and do some more tests. If the situation
> remains fixed then that's that! But if I run into further problems
> i.e. the "delete FF profile" approach turns out NOT to be a fix, I'll
> report back.
> let us know how you get on, should you decide to try different
> browsers in different machines.
>
>
> DDS

Thanks for your feedback. I've posted a question in the Firefox support
forum, to see whether there are any known issues which may be relevant.
Meanwhile, I'm going to try to narrow the problem down by, for example,
seeing whether email works with the firewall on, from a clean boot without
Firefox being started. I've already confirmed that simply exiting Firefox
*doesn't* fix it.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
Roger Mills <(E-Mail Removed)> wrote:

>
> Thanks for your feedback. I've posted a question in the Firefox
> support forum, to see whether there are any known issues which may be
> relevant. Meanwhile, I'm going to try to narrow the problem down by,
> for example, seeing whether email works with the firewall on, from a
> clean boot without Firefox being started. I've already confirmed that
> simply exiting Firefox *doesn't* fix it.

Update: Fresh boot, no browsers running, email works with firewall on. Start
up IE (not even Firefox) and email stops working.

So it looks as if *any* internet activity triggers this problem, and that it
probably has nothing to do with Firefox per se.

I haven't a clue where we go from here!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

>> Thanks for your feedback. I've posted a question in the Firefox
>> support forum,

> So it looks as if *any* internet activity triggers this problem, and that
> it probably has nothing to do with Firefox per se.

> I haven't a clue where we go from here!

Nor me, I'm afraid. I can only say the obvious things (check out the
microsoft news server for appropriate groups, Google, maybe as a
stab-in-the-dark guess try searching for "net" commands, ARP cache, hosts
file stuff).

Best of luck and please do post back if/when you find more evidence.

DDS

Roger Mills wrote:
> In an earlier contribution to this discussion,
> Roger Mills <(E-Mail Removed)> wrote:
>
>> Thanks for your feedback. I've posted a question in the Firefox
>> support forum, to see whether there are any known issues which may be
>> relevant. Meanwhile, I'm going to try to narrow the problem down by,
>> for example, seeing whether email works with the firewall on, from a
>> clean boot without Firefox being started. I've already confirmed that
>> simply exiting Firefox *doesn't* fix it.
>
> Update: Fresh boot, no browsers running, email works with firewall on. Start
> up IE (not even Firefox) and email stops working.
>
> So it looks as if *any* internet activity triggers this problem, and that it
> probably has nothing to do with Firefox per se.
>
> I haven't a clue where we go from here!

Try setting MTU to 1400.

I've had this sort of behavior intermittently when my internet 'goes
bad;' and some large packets get fragmented, and a piece never arrives.

I've also had very strange problems a bit like this cured by a router
firmware update.

Ato_Zee wrote:
>>> So it looks as if *any* internet activity triggers this problem, and
>>> that
>>> it probably has nothing to do with Firefox per se.
>
> When internet connection dies on one machine but not another,
> see if the dead one can ping www.google.com both by
> name and dotted quad IP address.
> 209.85.229.106 (not sure if Google change this
> occasionally, but you get the idea, you can do the ping
> to get the IP address on the good machine)
> Next do an ipconfig /all on both machines and compare
> the results.
> Compare the hosts files.
> And one common problem is too high an MTU sdetting,
> there are free utilities to fix this problem.

I half agree.

Too high an MTU should not cause things to crap out, but it does,
because some upstream router or switch is mangling packet fragmentation
and defragmentation.

So its not a local problem, its a remote problem, that has not a local
FIX, but a local *workaround*.

Fixing a crash on the M25 is clearing away the bodies, car and human,
and cleaning and repairing the road surface. Driving across london, is a
workaround ;-)


> Usually when things go pear shaped I just restore
> the OS in under 5 mins from the original image, plus
> the differential image taken when things worked.
> You just select the differential image of appropriate
> date. It helps if the OS is on its own drive or partition,
> with data, emails, bookmarks, newsgroups etc on another.

I just go :-

#ifconfig eth0 mtu 1400

Takes about 10 seconds.;-)

However its not the only problem that can cause these effects. Sometimes
the routers NAT cache seems to get screwed. Rebooting the router and
the client PC's will fix that for a while.

In an earlier contribution to this discussion,
Ato_Zee <(E-Mail Removed)> wrote:

>>> So it looks as if *any* internet activity triggers this problem, and
>>> that
>>> it probably has nothing to do with Firefox per se.
>
> When internet connection dies on one machine but not another,
> see if the dead one can ping www.google.com both by
> name and dotted quad IP address.

But the internet connection *isn't* dying - browsing works ok - it's just
email that dies when the router's firewall is on, returning an 800ccc0e
error when I try to connect to any pop server.

On my other PCs, email works with the router's firewall is *on*. Any clues?
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In an earlier contribution to this discussion,
The Natural Philosopher <(E-Mail Removed)> wrote:

> Roger Mills wrote:
>> In an earlier contribution to this discussion,
>> Roger Mills <(E-Mail Removed)> wrote:
>>
>>> Thanks for your feedback. I've posted a question in the Firefox
>>> support forum, to see whether there are any known issues which may
>>> be relevant. Meanwhile, I'm going to try to narrow the problem down
>>> by, for example, seeing whether email works with the firewall on,
>>> from a clean boot without Firefox being started. I've already
>>> confirmed that simply exiting Firefox *doesn't* fix it.
>>
>> Update: Fresh boot, no browsers running, email works with firewall
>> on. Start up IE (not even Firefox) and email stops working.
>>
>> So it looks as if *any* internet activity triggers this problem, and
>> that it probably has nothing to do with Firefox per se.
>>
>> I haven't a clue where we go from here!
>
> Try setting MTU to 1400.
>
> I've had this sort of behavior intermittently when my internet 'goes
> bad;' and some large packets get fragmented, and a piece never
> arrives.
> I've also had very strange problems a bit like this cured by a router
> firmware update.

I've reduced MTU to 1400 - but it makes no difference. Any other ideas?

[Please see my other post (about 2 minutes ago) for a fuller description of
the problem]
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!