Raspberry PI Odd Network Issue - Can't access LAN hosts

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ajobbins

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#111270 29-Oct-2012 11:43

Got my Raspberry Pi from Element14 a couple of days ago and have started to have a play with Raspbmc. I was having trouble accessing content on other hosts, with XBMC telling me it couldn't find a path to the host. I figured it was just an XBMC issue until I started playing around a bit more.

I loaded up images for Raspian "Wheezy" and Incredible Pi PBX onto seperate SD cards and it quickly became apparent that the network issue wasn't specific to the XBMC install I had.

I did some playing around and established that on all distributions I have tried the following happens:
- I can communicate with my Router (192.168.1.1) and out to the internet fine from the Pi
- I can connect to (ping/ssh/http/whatever) to the Raspberry Pi (192.168.1.70 assigned by DHCP) from the LAN
- I CANNOT connect to any LAN hosts (All on 192.168.1.x) from the Pi (Destination host unreachable, etc)

I have tried the following:
- 3 different distributions running on 3 seperate SD card (as above)
- I have tried manually setting an IP address and subnet mask
- I have tried a totally different router and network cables
- Tried with vanilla installs of the distros - no changes from the default
- Tried a different subnet (Setup hosts on a new network (inc hardware) on 192.168.2.x)

Basically, as far as I can tell, I have eliminated all possible causes apart from the Pi hardware itself, but it's just an odd problem and I can't possible see how a hardware fault would cause such a specific connectively issue.

Has anyone seen anything like this, or can you suggest anything I can try to resolve?

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#708297 29-Oct-2012 11:46

I'll try this tonight if nobody else has figured it out by then.

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muppet

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#708307 29-Oct-2012 12:04

Are you learning ARP addresses for the hosts you can't ping? What does your arp table look like on the PI?

One thing to check is that the MAC address your PI has isn't also allocated to another device on your LAN. Very unlikely, but could cause the problems you're seeing (which sound like ARP problems)

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#708312 29-Oct-2012 12:07

I had a similar issue with mine. Found out over the weekend that my router stopped bridging the 5Ghz and 2.4Ghz networks. The Pi is on 2.4 and everything else is on 5Ghz. Still not sure how to fix it (DD-WRT).

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ajobbins

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#708333 29-Oct-2012 12:28

muppet: Are you learning ARP addresses for the hosts you can't ping? What does your arp table look like on the PI?

One thing to check is that the MAC address your PI has isn't also allocated to another device on your LAN. Very unlikely, but could cause the problems you're seeing (which sound like ARP problems)

What is the best way to check this? It's not a MAC issue - I tried it on a separate router/switch with only 1 other device (my laptop) and all have unique MACs.

Communicating to the Pi is fine from the LAN - The Pi just can't see anything else.

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ajobbins

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#708335 29-Oct-2012 12:28

magu: I had a similar issue with mine. Found out over the weekend that my router stopped bridging the 5Ghz and 2.4Ghz networks. The Pi is on 2.4 and everything else is on 5Ghz. Still not sure how to fix it (DD-WRT).

I've taken WiFi completely out of the equation. This is all on wired LAN

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muppet

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#708337 29-Oct-2012 12:36

ajobbins:
muppet: Are you learning ARP addresses for the hosts you can't ping? What does your arp table look like on the PI?

One thing to check is that the MAC address your PI has isn't also allocated to another device on your LAN. Very unlikely, but could cause the problems you're seeing (which sound like ARP problems)

What is the best way to check this? It's not a MAC issue - I tried it on a separate router/switch with only 1 other device (my laptop) and all have unique MACs.

Communicating to the Pi is fine from the LAN - The Pi just can't see anything else.

Assuming you have a Linux distro on it, "arp -n" as root (or sudo arp -n) should show you what the PI knows about.

For example, from my Linux box at home:

root@micro:/media/flash/tim# arp -n
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.0.55             ether   00:c0:b7:6b:56:f3   C                     wlan1
192.168.0.5              ether   68:09:27:22:35:22   C                     wlan1
192.168.0.1              ether   00:26:f2:42:f0:7c   C                     wlan1

I can see my APC Board (.55) the Router itself (.1) and some other dingus at .5

If you can see the ARP addresses for the devices you're not able to contact, it would imply the problem is somewhere else.

Also: Have you checked the subnet mask you're being given? If you get given the wrong subnet mask issues like what you've posted crop up as your PI, rather than arping for a device, will send the request to the router.

ajobbins

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#708391 29-Oct-2012 13:15

I'll have to have a look when I get home. I remotely rebooted it and it hasn't come back online.

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magu

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#708402 29-Oct-2012 13:29

ajobbins:
muppet: Are you learning ARP addresses for the hosts you can't ping? What does your arp table look like on the PI?

One thing to check is that the MAC address your PI has isn't also allocated to another device on your LAN. Very unlikely, but could cause the problems you're seeing (which sound like ARP problems)

What is the best way to check this? It's not a MAC issue - I tried it on a separate router/switch with only 1 other device (my laptop) and all have unique MACs.

Communicating to the Pi is fine from the LAN - The Pi just can't see anything else.

Incorrect netmask, maybe?

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ajobbins

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#708411 29-Oct-2012 13:46

magu: Incorrect netmask, maybe?

I checked that. DHCP is dishing out 255.255.255.0 which I think is correct. This is the same as the other hosts on the network get, and they can all talk to each other fine.

Tried setting it manually but didn't help

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nzkc

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#708422 29-Oct-2012 14:17

Are the "hosts" all Windows machines and are they all in the same "Home Network"? Cause your Pi wont be and if you don't allow sharing outside your home network it wont work. Had this problem myself (not just with a Pi either).

ajobbins

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#708424 29-Oct-2012 14:21

nzkc: Are the "hosts" all Windows machines and are they all in the same "Home Network"? Cause your Pi wont be and if you don't allow sharing outside your home network it wont work. Had this problem myself (not just with a Pi either).

Mostly yes, but I can access the windows hosts from my iPad, and my Android phone over the WLAN

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nzkc

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#708427 29-Oct-2012 14:24

Does your router have a DMZ and you've somehow managed to get your Pi into that rather than your LAN?

nzkc

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#708428 29-Oct-2012 14:25

nzkc: Does your router have a DMZ and you've somehow managed to get your Pi into that rather than your LAN?

Ahhh I see you tried a different router - unlikely to be this then.

ajobbins

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#708433 29-Oct-2012 14:27

nzkc: Does your router have a DMZ and you've somehow managed to get your Pi into that rather than your LAN?

No. DMZ not used. Couple of port forwards to my reverse web proxy box but that shouldn't matter.

Tested with a totally different router too and same issue.

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gstarkey

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#708472 29-Oct-2012 15:19

This is very odd.

Can you post the output of the following commands, when run on the Pi:
ifconfig
netstat -r

Thanks

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