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Intermittent "destination address unreachable" when pining router



 
 
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  #11  
Old August 28th 18, 12:19 PM posted to uk.telecom.broadband
NY
external usenet poster
 
Posts: 433
Default Intermittent "destination address unreachable" when pining router

"NY" wrote in message
o.uk...
"Graham J" wrote in message
news
NY wrote:

[snip]

If I happen to see the guy that runs the cottage, I'll ask whether his
own internet in the house goes off at the same time as the one in the
cottage (ie is it a router problem or a wireless extender problem). I
think an extender is involved since the SSIDs are EXT2-BTHomeSpot-72G
and EXT5-BTHomeSpot-72G (2 or 5 for 2.4 or 5 GHz).


So can you speculate - is the extender in the cottage, and the router in
another building? You could wander around the site with inSSIDer running
on your laptop - or more discreetly with a similar program runing on your
smartphone ...

I'm reluctant to reveal too much knowledge or he may try to rope me in
to investigate, which would make it a busman's holiday!


It may well be easier to solfe the problem than write about it in the
newsgroup!

And you may find that questioning the WiFi reliability may be on a par
with criticising somebody's driving - not taken well!!!


When the connection comes back again I'll set a continuous ping running
and see if ping time gradually increases until it fails totally.


Further info now:

I ran a "ping 192.168.1.254 -t" to the router's gateway address. Out of 940
packets, times we min 4 ms, max 56 ms, av 7 ms.- until I began to get "no
reply". That happened at same time as wifi icon got a yellow exclamation
mark and Teamserver connection to remote PC (back home) dropped out (*)

After this had happened, I checked with ipconfig, and IP was still sensible
values (ie IP in range 192.168.1.x). I connected to another network
(tethering to my mobile phone internet) and showed that IP details changed
to totally different subnet.

Then I connected to original network and IP details were back to 192.168.1.x
values. But couldn't ping router.

So... even when router cannot be pinged, its DHCP server can still hand out
valid IP addresses. So the router is not totally dead even at those times.


(*) My usenet server is configured to reject connections from any ISP other
than the one that runs it, so I have to log onto my PC at home to access
news. OK, I know I could go for an independent usenet provider like eternal
september...

  #12  
Old August 28th 18, 12:50 PM posted to uk.telecom.broadband
Graham J[_2_]
external usenet poster
 
Posts: 723
Default Intermittent "destination address unreachable" when pining router

NY wrote:

[snip]

When the connection comes back again I'll set a continuous ping
running and see if ping time gradually increases until it fails totally.


Further info now:

I ran a "ping 192.168.1.254 -t" to the router's gateway address. Out of
940 packets, times we min 4 ms, max 56 ms, av 7 ms.- until I began to
get "no reply". That happened at same time as wifi icon got a yellow
exclamation mark and Teamserver connection to remote PC (back home)
dropped out (*)

After this had happened, I checked with ipconfig, and IP was still
sensible values (ie IP in range 192.168.1.x). I connected to another
network (tethering to my mobile phone internet) and showed that IP
details changed to totally different subnet.

Then I connected to original network and IP details were back to
192.168.1.x values. But couldn't ping router.

So... even when router cannot be pinged, its DHCP server can still hand
out valid IP addresses. So the router is not totally dead even at those
times.


Er, no. Connecting to the original network is purely a WiFi function in
that your laptop has remembered the security key for that SSID and
establishes a Data Link (i.e. layer 2 in the OSI model, see:
https://en.wikipedia.org/wiki/OSI_model)
However your laptop's DHCP client can't actually contact the DHCP
server. I think it remembers the IP address it most recently used which
is associated with the MAC address of the remote end of the WiFi link.

I think you could test this. Having connected to a another network
(your mobile phone internet), then disconnected - at this stage reboot
your laptop - this should flush any ARP cache - and delete the WiFi
profile for the suspicious WiFi. Then try to connect to it. I expect
it to announce that it can see WiFi signals, to show the relevant SSID,
and ask for the security key. When you provide the key it will connect
to the remote WiFi node, but you will see the blue circle indicating
that it is trying to contact the DHCP server. It will fail, and at this
stage ipconfig should show an autoconfiguration IP address.

I can test this here later - I have an access point that I can
disconnect from the LAN.

Per your other post, you now know the IP address of the WiFi extender.
Normally you should be able to ping it. Then test whether you can ping
it while the fault is present. Check first that your laptop does indeed
have the correct IP address, if not set it statically for this test.
(Also, the DHCP server in the router should remember the IP address used
for the extender, even across a power cycle [it being a BT Business
Smarthub], so regardless of whether the extender got its IP from the
DHCP server or it was statically assigned in the device, there should
not be any clashes.)

This test should show more about the connection between the router and
the extender.

Which you could investigate: the router should show whether the extender
is connected by wire or wirelessly - the BT device probably has a pretty
diagram ...

--
Graham J





 




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