Unable to ping machines on a wireless ad-hoc network

Pieman86 · 11-10-2006, 01:27 PM

Hi

I have two laptops with wireless enabled (one's running Debian, the other's running Gentoo, and they both have Intel PRO/Wireless cards). Everything seems to be set up correctly, because I can connect to the Internet just fine using an access point.

I recently tried to get the machines connected in ad-hoc mode. I'm not very experienced with wireless networking, but I think I followed the right steps. The problem is that I cannot use either machine to ping the other one. This is what I did:

MACHINE 1 (wireless interface is eth1)
iwconfig eth1 mode Ad-Hoc essid mynet channel 11 key off
ifconfig eth1 10.10.10.10 netmask 255.255.255.0 up

MACHINE 2 (wireless interface is eth0)
iwconfig eth0 mode Ad-Hoc essid mynet channel 11 key off
ifconfig eth0 10.10.10.11 netmask 255.255.255.0 up

Both of them associated with the "mynet" network and accepted the static IP addresses I assigned them. Here's the relevant output from iwconfig on the two machines afterwards:

Code:

eth1      IEEE 802.11g  ESSID:"mynet"
          Mode:Ad-Hoc  Frequency:2.462 GHz  Cell: 02:12:F0:4F:41:40
          Bit Rate=54 Mb/s   Tx-Power=20 dBm

Code:

eth0      IEEE 802.11g  ESSID:"mynet"
          Mode:Ad-Hoc  Frequency:2.462 GHz  Cell: 02:12:F0:4F:41:40
          Bit Rate=54 Mb/s   Tx-Power=20 dBm   Sensitivity=8/0

So far, everything looks like it's working properly. I can ping the first machine from itself over the wireless interface. But I can't reach the other machine:

sanmao@localghost:~$ ping -I eth1 10.10.10.10
PING 10.10.10.10 (10.10.10.10) from 10.10.10.10 eth1: 56(84) bytes of data.
64 bytes from 10.10.10.10: icmp_seq=1 ttl=64 time=0.075 ms
64 bytes from 10.10.10.10: icmp_seq=2 ttl=64 time=0.064 ms

--- 10.10.10.10 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.064/0.069/0.075/0.010 ms
sanmao@localghost:~$ ping -I eth1 10.10.10.11
PING 10.10.10.11 (10.10.10.11) from 10.10.10.10 eth1: 56(84) bytes of data.
From 10.10.10.10 icmp_seq=2 Destination Host Unreachable
From 10.10.10.10 icmp_seq=3 Destination Host Unreachable
From 10.10.10.10 icmp_seq=4 Destination Host Unreachable
From 10.10.10.10 icmp_seq=6 Destination Host Unreachable
From 10.10.10.10 icmp_seq=7 Destination Host Unreachable
From 10.10.10.10 icmp_seq=8 Destination Host Unreachable

--- 10.10.10.11 ping statistics ---
8 packets transmitted, 0 received, +6 errors, 100% packet loss, time 7000ms
, pipe 3

I've deactivated the firewalls and other network interfaces on both machines, but it still doesn't work.

I searched the Internet for a bit and found that other people have had similar problems in the past, but I haven't been able to find any answers to this problem. I'm obviously missing something important, and would really appreciate any suggestions on what's going wrong.

Thanks a lot
Simon

camorri · 11-11-2006, 06:24 AM

After reading your post, I have two things you can look at. The first is the sub-net mask for a class A network should be 255.0.0.0. ( I don't think this is what is stopping the pins to work, but you may want to change it.

The one machine's card is eth1. Is there an eth0 on that machine? If so, have you a default route set on eth0? What have you got in the routing table for the 10.x.x.x sub-net? You may only need to enter a static route for this sub-net.

Other than those two things, everyting looks good...

Hope this helps.

Pieman86 · 11-12-2006, 05:23 AM

Hi camorri

Thanks for your post! I changed the subnet mask as you suggested (forgot 10.x.x.x was a private Class A).

Here's the output of "route" on both computers:

eth1 machine:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.0.0.0        *               255.0.0.0       U     0      0        0 eth1

eth0 machine:

Code:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.0.0.0        *               255.0.0.0       U     0      0        0 eth0
loopback        *               255.0.0.0       U     0      0        0 lo

Nothing is going out on eth0 of the first machine, as far as I can see. I'm also not really sure how to set up an appropriate route for the first machine (adding a default gateway won't help, will it?). If you have any further suggestions, I'd be really grateful.

Thanks again
Simon

camorri · 11-12-2006, 09:54 AM

I think your problem is in fact your routing table. You can add a route with the command 'route add' as the route user. Here is a sample i cut and pasted from the route man page.

Quote:

route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0

This would add a sub-net to eth0. All you need to do to test it is do the route add on both machines on the appropriate interface. You can see with the route command if it got added to the routing table. That change is
there until you boot, or remove it with 'route del' command. I'm using WebMin to manage my system. I can use it to add, delete routes, hosts etc. It accesses the correct system file to store static and default routes. I'm sure if I poke around, I can figure out what file you need to edit to make it permanent.

A default route is where a packet will get sent if the kernel doesn't know what to do with it. If there is no default, and the kernel can't decide what to do with a packet, it doesn't get sent anywhere. Not good. In my case, I always set a default, for my system, it is the address of my router.

Let me know how it goes.

Pieman86 · 11-16-2006, 03:29 PM

Hi camorri.

Thanks for all your help, but I haven't managed to get it working yet. Regarding the output of "route" that I posted earlier, didn't that already show that a route existed for the 10.x.x.x subnet on both machines? I also don't know what to set for my default route, as I thought the whole point of an ad-hoc network was that there is no central router.

Maybe there's just something wrong with the computers. Strangely, I can use arping to reach Machine 1 from Machine 2, but not the other way around. I've gone back to using a wireless access point for now, anyway.

Regards
Simon