Weird network problem with ubuntu only

[rklauco]

I am running out of ideas here.

I run small home server using ubuntu and dnsmasq.
Everything worked fine until few days ago, when I noticed I am unable to ssh/ping other ubuntu machine on my private lan.
To explain:

• all clients have correct static or dynamic address delivered using DHCP
• all DNS requests are resolved properly, returning IPv4 addresses as expected
• all network clients are able to access internet
• all network clients are able to access the server
• all non-ubuntu network clients can be pinged, accessed using ssh/http and so on (openWRT, debian)
• ubuntu clients cannot access other ubuntu clients with the exception of the server

Example:

• server IP 192.168.1.1, client1 IP 192.168.1.2 (ubuntu), client2 IP 192.168.1.3 (ubuntu), client3 192.168.1.4(openwrt)
• on server, ping client1 works fine, ping client2 works fine
• on client1, ping 192.168.1.1 works fine, ping 192.168.1.3 ends up with "destination host unreachable"
• on client2, ping 192.168.1.2 ends up with "destination host unreachable"
• on client1, ping 192.168.1.4 works fine
• on client3, ping 192.168.1.2 or 192.168.1.3 works fine

I thought it has something to do with IPv6, but disabling it did not help.
Also, I am trying to ping/ssh using IPv4 address and hostname with no success here.
Please, advice what should I look into next.

[papibe]

Hi rklauco.

Could you explain a little bit the 'topology' of your network? That is, how the devices are connected to each other?

Could you also post these commands from both the server and client1?

ifconfig

route -n

Regards.

[rklauco]

Ifconfig from one of the clients:

eth0      Link encap:Ethernet  HWaddr 64:31:50:8b:7f:f0  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:16 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:4833 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4833 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:467208 (467.2 KB)  TX bytes:467208 (467.2 KB)

vmnet1    Link encap:Ethernet  HWaddr 00:50:56:c0:00:01  
          inet addr:172.16.233.1  Bcast:172.16.233.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:21 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

vmnet8    Link encap:Ethernet  HWaddr 00:50:56:c0:00:08  
          inet addr:192.168.82.1  Bcast:192.168.82.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:21 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

wlan0     Link encap:Ethernet  HWaddr ac:81:12:59:7f:92  
          inet addr:192.168.10.12  Bcast:192.168.10.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:59396 errors:0 dropped:0 overruns:0 frame:0
          TX packets:47387 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:55490693 (55.4 MB)  TX bytes:10357342 (10.3 MB)

route -n from the same client:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.10.1    0.0.0.0         UG    0      0        0 wlan0
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 wlan0
172.16.233.0    0.0.0.0         255.255.255.0   U     0      0        0 vmnet1
192.168.10.0    0.0.0.0         255.255.255.0   U     9      0        0 wlan0
192.168.82.0    0.0.0.0         255.255.255.0   U     0      0        0 vmnet8

The same from server - ifconfig first:

eth0      Link encap:Ethernet  HWaddr 00:1d:60:08:ab:66  
          inet addr:192.168.10.1  Bcast:192.168.10.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5097848 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8577878 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:864823625 (864.8 MB)  TX bytes:2901246167 (2.9 GB)
          Interrupt:43 Base address:0x6000 

eth1      Link encap:Ethernet  HWaddr 00:13:3b:14:05:be  
          inet addr:192.168.60.69  Bcast:192.168.60.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:9569074 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12959646 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:4191313000 (4.1 GB)  TX bytes:517660037 (517.6 MB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:162514 errors:0 dropped:0 overruns:0 frame:0
          TX packets:162514 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:14704287 (14.7 MB)  TX bytes:14704287 (14.7 MB)

and route -n from the server:

0.0.0.0         192.168.60.1    0.0.0.0         UG    100    0        0 eth1
192.168.10.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0
192.168.60.0    0.0.0.0         255.255.255.0   U     0      0        0 eth1

I see no problem, all other clients have correct routing and IP addresses, too, all of them are able to connect to internet and non-ubuntu clients.

[papibe]

Thanks.

Have you enabled IP forwarding in your server?

Could you post the result of this command?

grep forward /etc/sysctl.conf

Regards.

BTW: I didn't get your topology.