Sometimes can't access device on local network

[Colin Law]

On 31 December 2017 at 15:02, Colin Law <clanlaw at gmail.com> wrote:

> On 31 December 2017 at 12:13, Colin Law <clanlaw at gmail.com> wrote:
>
>> I have an odd situation that occurs occasionally.  I have a conventional
>> wired local network (192.168.1.nnn) with in addition some devices connected
>> via wifi. The main router (192.168.1.1) is also the wifi hub.
>>
>> Consider three of these machines. A, B and C.  A and B are wired and C is
>> wifi, all with fixed IP addresses.
>>
>> Normally all is well but occasionally I am not able to access C from A.
>> When I ping it I get
>> $ ping 192.168.1.85
>> PING 192.168.1.85 (192.168.1.85) 56(84) bytes of data.
>> From 192.168.1.92 icmp_seq=1 Destination Host Unreachable
>>
>> 92 is the device I am running on (A).
>>
>> However I am able to access B from A and also able to access C from B,
>> which is particularly odd. So, even though I cannot ssh into C from A, I
>> can ssh into B from A and from there ssh into C.
>>
>
> The plot thickens! I see now that C is not responding to arp requests. Any
> machines that already have C in their arp table continue to be able to
> communicate but any that do not cannot. Now I need to work out why it is
> not responding.
>

It was not so much that C was not responding to ARP requests, but that the
router (a BT Home Hub running LEDE) was not forwarding them across the wifi
for some reason. Re-booting the router fixed it.  Presumably it will happen
again in a couple of weeks.  I can't find anything similar in a short
google search. I will post a question on the LEDE forum.

Cheers and have a good new year

Colin


> Colin
>
>
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