RaspISteve
Posts: 100
Joined: Wed Oct 24, 2012 9:15 pm
Location: Cheltenham, UK

Ping Blind Spot Between two IP Address [SOLVED]

Mon Sep 05, 2016 2:37 pm

Guys,
I have a P3B and Ubuntu laptop and one or other (or both) seem to be sulking and won't talk to each other. Specifically I can neither ping nor ssh between them. Both use DHCP are wireless connected all both are on my LAN for all other purposes.

Both display the same ping error message where the pinging computer reports using its own IP address as "Destination Host Unreachable". The error messages on each computer are symmetrical.

Code: Select all

:~ $ ping raspberrypi3b
PING raspberrypi3b.lan (192.168.1.105) 56(84) bytes of data.
From stevew-Inspiron-510m.lan (192.168.1.104) icmp_seq=1 Destination Host Unreachable <snipped>
Both report ARP table (using arp -a) as:
"dest name.lan dest IP address at <incomplete> on wlan0"

Code: Select all

:~ $ arp -a
raspberrypi3b.lan (192.168.1.105) at <incomplete> on wlan0
dsldevice.lan (192.168.1.15) at 08:76:ff:7f:18:02 [ether] on wlan0 <snipped>
However, both systems are very definitely on my LAN as both see all other systems, the gateway the web and can resolve each others hostnames. The problem does not follow the SD card in the P3B, have tried a current Jesse and RetroPie SD card and both show the same problem.

A bonus during all this was the P3B also put the ping command into super user world which I've sorted (had to reinstall it (Huh!)). I have found an exact mirror of my problem described on the web asking for a solution but nothing definitive was available.

So, both system work with all other devices on my LAN but I can't or they won't complete a ping or ssh exchange between them. Basically they are both sulking and I want them to stop so that I can get on. Have tried setting one unit to a different static IP but no change.
Last edited by RaspISteve on Mon Sep 05, 2016 8:50 pm, edited 1 time in total.
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wh7qq
Posts: 1475
Joined: Thu Oct 09, 2014 2:50 am

Re: Ping Blind Spot Between two IP Address

Mon Sep 05, 2016 6:59 pm

As both are on wireless and both reach the WAN, the problem could be in your wireless router...maybe it isn't configured to allow wireless devices to talk to each other. Put the Pi3 on an ethernet connection and see what happens.

stderr
Posts: 2178
Joined: Sat Dec 01, 2012 11:29 pm

Re: Ping Blind Spot Between two IP Address

Mon Sep 05, 2016 8:02 pm

RaspISteve wrote:Guys,
I have a P3B and Ubuntu laptop and one or other (or both) seem to be sulking and won't talk to each other.
Can they ping a third machine, a phone, the router? Start using the actual ip addresses and not names. Make sure they can ping themselves as well.

RaspISteve
Posts: 100
Joined: Wed Oct 24, 2012 9:15 pm
Location: Cheltenham, UK

Re: Ping Blind Spot Between two IP Address

Mon Sep 05, 2016 8:31 pm

wh7qq ,
brilliant! Think you've got it in one. Thank you.

I found another wireless PI and can't get to that either. Nor can I raise my moby or TV also in wifi.

My router is a "Thomson TG585 v8". I've just given the thing a once over and I'm stuffed if I can find an option to either allow routing between WiFi units or indeed to prevent it. Just occurs to ask "Why would I not want to connect between systems on WiFi? Duh!".

Guess I'm just lucky the <kin> thing does wired Ethernet to WiFi. I need to investigate this one, maybe try my old router. I'm sure I've routed across WiFi perhaps it was with the old router. Anyway.. THANX.
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