Access to specific web site

Hello

Here's an interesting one.
I'm with O2, who have been giving good performance for about a year.
When I try and access (using IE, firefox, or outlook)
webmail.insert_my_company_name.com using a wired PC (not WiFi), then
sometimes this attempt will timeout. Then it stays like this until I reboot
the router. I have tried two routers and it is the same with either. My IP
address, although not static, doesn't change after a reboot.
When access to this site fails, I CAN access it using my iPhone when I turn
its WiFi off (so it uses the cellular network). With WiFi turned on (on the
iPhone) it too fails, as expected. And my work colleagues have no issues at
all, even during periods where I cannot connect.
Any idea what causes this?
TIA.

"Andy Burns" <(E-Mail Removed)> wrote in message
newsJGdnX6pXP-(E-Mail Removed)...
> Grumps wrote:
>
>> When access to this site fails, I CAN access it using my iPhone when I
>> turn its WiFi off (so it uses the cellular network). With WiFi turned on
>> (on the iPhone) it too fails, as expected. And my work colleagues have no
>> issues at all, even during periods where I cannot connect.
>> Any idea what causes this?
>
> Weird MTU settings on the router? O2 use bridging rather than routing over
> the ADSL link.

Thanks,
The 2 routers are the O2 supplied one and a WAG200G. The settings do seem to
be correct (briding mode as you say, and an MTU of 1500).
But why only the one site? Access is ok for ages, then it fails and will not
connect (until a reboot). And this has only recently started to happen.
Actually, only since O2's cellular network went tits-up!

On Sat, 25 Jul 2009 22:23:37 +0100, "Grumps" <(E-Mail Removed)> wrote
this:

>Here's an interesting one.

Interesting! You really should get out more.

On Sat, 25 Jul 2009 23:13:56 +0100, Andy Burns wrote:

> Grumps wrote:
>
>> The 2 routers are the O2 supplied one and a WAG200G. The settings do
>> seem to be correct (briding mode as you say, and an MTU of 1500).
>
> See it it makes a difference knocking it down to 1492
>
>> But why only the one site?
>
> Some sites end up with "daft" settings on routers/firewalls at their end
> that set a smaller MTU and don't allow fragmentation.

And blocking ICMP traffic will bork any attempt at path discovery ?
Perhaps make sure you are not dropping all ICMP .

"R Johnson" <(E-Mail Removed)> wrote in message
news:4a6bf8f3$0$2482$(E-Mail Removed)...
> On Sat, 25 Jul 2009 23:13:56 +0100, Andy Burns wrote:
>
>> Grumps wrote:
>>
>>> The 2 routers are the O2 supplied one and a WAG200G. The settings do
>>> seem to be correct (briding mode as you say, and an MTU of 1500).
>>
>> See it it makes a difference knocking it down to 1492
>>
>>> But why only the one site?
>>
>> Some sites end up with "daft" settings on routers/firewalls at their end
>> that set a smaller MTU and don't allow fragmentation.
>
> And blocking ICMP traffic will bork any attempt at path discovery ?
> Perhaps make sure you are not dropping all ICMP .

Thanks, but no idea what that means
When it works, it works, and I can tracert it.
When it fails, it fails untill a router reboot (unless that's just a
coincidence), and I can't tracert it.

Grumps wrote:
> "R Johnson" <(E-Mail Removed)> wrote in message
> news:4a6bf8f3$0$2482$(E-Mail Removed)...
>> On Sat, 25 Jul 2009 23:13:56 +0100, Andy Burns wrote:
>>
>>> Grumps wrote:
>>>
>>>> The 2 routers are the O2 supplied one and a WAG200G. The settings do
>>>> seem to be correct (briding mode as you say, and an MTU of 1500).
>>> See it it makes a difference knocking it down to 1492
>>>
>>>> But why only the one site?
>>> Some sites end up with "daft" settings on routers/firewalls at their end
>>> that set a smaller MTU and don't allow fragmentation.
>> And blocking ICMP traffic will bork any attempt at path discovery ?
>> Perhaps make sure you are not dropping all ICMP .
>
> Thanks, but no idea what that means
> When it works, it works, and I can tracert it.
> When it fails, it fails untill a router reboot (unless that's just a
> coincidence), and I can't tracert it.
>
>
I had similar years ago, and the site actually recommended a firmware
upgrade on the router, which fixed it.

But that would seem to be a very long shot in this case..

"The Natural Philosopher" <(E-Mail Removed)> wrote in message
news:h4h5c7$dsc$(E-Mail Removed)...
> Grumps wrote:
>> "R Johnson" <(E-Mail Removed)> wrote in message
>> news:4a6bf8f3$0$2482$(E-Mail Removed)...
>>> On Sat, 25 Jul 2009 23:13:56 +0100, Andy Burns wrote:
>>>
>>>> Grumps wrote:
>>>>
>>>>> The 2 routers are the O2 supplied one and a WAG200G. The settings do
>>>>> seem to be correct (briding mode as you say, and an MTU of 1500).
>>>> See it it makes a difference knocking it down to 1492
>>>>
>>>>> But why only the one site?
>>>> Some sites end up with "daft" settings on routers/firewalls at their
>>>> end
>>>> that set a smaller MTU and don't allow fragmentation.
>>> And blocking ICMP traffic will bork any attempt at path discovery ?
>>> Perhaps make sure you are not dropping all ICMP .
>>
>> Thanks, but no idea what that means
>> When it works, it works, and I can tracert it.
>> When it fails, it fails untill a router reboot (unless that's just a
>> coincidence), and I can't tracert it.
> I had similar years ago, and the site actually recommended a firmware
> upgrade on the router, which fixed it.
>
> But that would seem to be a very long shot in this case..

Anything is worth a shot. Funny as it happens using two different make
routers.

"Stephen" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Sat, 25 Jul 2009 22:23:37 +0100, "Grumps" <(E-Mail Removed)>
> wrote:
>
>>Hello
>>
>>Here's an interesting one.
>>I'm with O2, who have been giving good performance for about a year.
>>When I try and access (using IE, firefox, or outlook)
>>webmail.insert_my_company_name.com using a wired PC (not WiFi), then
>>sometimes this attempt will timeout. Then it stays like this until I
>>reboot
>>the router. I have tried two routers and it is the same with either. My IP
>>address, although not static, doesn't change after a reboot.
>>When access to this site fails, I CAN access it using my iPhone when I
>>turn
>>its WiFi off (so it uses the cellular network). With WiFi turned on (on
>>the
>>iPhone) it too fails, as expected. And my work colleagues have no issues
>>at
>>all, even during periods where I cannot connect.
>>Any idea what causes this?
>
> it might be that their DNS servers are overloaded - this used to
> happen on VM a lot.
>
> Once you have the name to IP mapping in the cache, it "just works".
>
> make a note of the IP address, and try via that when it is broken
> (which should be reliable if all you have is a DNS issue).

Thanks. I spent a good half hour on their freephone support number. Went
through a lot of things, mostly obvious, but without a solution. They will
investigate and call me back tomorrow.
I can ping the address via my iPhone (connected via 3G and not my broadband)
and this works ok. The numerical IP returned is the same one that tracert
uses on the PC, but which fails.

"Ato_Zee" <(E-Mail Removed)> wrote in message
news:th1bm.16270$(E-Mail Removed)2...
>
>> make a note of the IP address, and try via that when it is broken
>> (which should be reliable if all you have is a DNS issue).
>
> And have a quick look at your hosts file, unlikely to
> be the source of the problem, but worth looking.
> Check your MTU setting.
> You may need to use diagnostic tools to sort it.
> Tracert, ping, pathping, and if all else fails a
> packet sniffer like Wireshark that shows
> what's going out, and what, if anything, is coming
> back.
> What you have to establish is how far the
> attempt is getting, is it blocked at your
> firewall, router, or getting to your ISP and
> then failing.
>
>> I have tried two routers and it is the same with either.
>
> Which makes it sound like your config, hence
> the hosts file and MTU check suggestion.

Thanks.
Using tracert shows that it always gets to my ISP.
When it fails, if I reboot the router then it works.
My IP is the same before and after reboot.
The target numerical IP is the same before and after reboot.
I get exactly the same behaviour with two routers.
I can always ping this address, and access the webmail.my_comapany_name.com
site using the iPhone via 3G.
I haven't got wireshark, but I'll have a play with pathping.
I've just done a reboot and it's working fine. I'll waut until it fails and
make more tests.
Ta.
Very strange!