How to connect to two wired networks

[cogitordi]

I have Ubuntu (10.04 LTS) on a PC with two network ports. Both ports work.

I have two LANs: LAN A has the Internet connection (through a router/switch), and LAN B has a router/switch with no WAN connection; LAN B has access to my files on NAS. I keep them separate for security.

I have an M-Windows box that is connected to both networks. To make the box see both networks, the network port connected to LAN B has a static IP address and no gateway is specified.

So I know how to achieve my goal with M-Windows, but I can't make it work in Linux. IFCONFIG shows that I have eth0 and eth1 for LAN A and LAN B; I do have Internet access through LAN A; the network port for LAN B shows a valid address. But I can't see the devices on LAN B.

I've tried editing /etc/network/interfaces to specify a static IP for LAN B, then restarting init.d. Nothing seems to work.

Is it just my ignorance or is this really a difficult thing to accomplish?

[Jonathan L]

IFCONFIG shows that I have eth0 and eth1 for LAN A and LAN B; I do have Internet access through LAN A; the internet [ethernet?] port for LAN B shows a valid address. But I can't see the devices on LAN B.

Hi

It's a perfectly reasonable thing to do and quite common. It's normally straightfoward unless you have overlapping network addressing. The only thing at all unusual is you say that the non-WAN network B has a router/switch attached to it: I presume it's an ADSL router with no ADSL plugged in, so it behaves just as an ethernet switch?

What addresses are you using, and how are you doing your name resolution for the NAS devices? I'd check your routes on your Ubuntu machine, and try pinging them by number, if you haven't already done so.

Also: are you running 10.04 server or desktop?

Kind regards,
Jonathan.

[cogitordi]

The only thing at all unusual is you say that the non-WAN network B has a router/switch attached to it: I presume it's an ADSL router with no ADSL plugged in, so it behaves just as an ethernet switch?

Correct, it is a modem-router with no WAN. I'm using it to serve IP addresses (DHCP) to a number of NAS devices. It is at 10.0.0.1.

try pinging them by number

PING to 10.0.0.1 fails (no successful delivery of packets).

Also: are you running 10.04 server or desktop?

It's the desktop version, 64b.

My LAN A router is at 192.168.1.1.

The ROUTE command shows everything that I've described.

[Jonathan L]

Hi again Cogito

With LAN A having 10.0.1.1 and LAN B having 10.0.0.1 my guess would be to check the netmasks on both sides. After that I'd check link lights. After that I'd try tcpdump or wireshark to see if my packets were going out the wrong port.

Hope that's helpful.

Kind regards,
Jonathan.

[cogitordi]

LAN A is 192.168.1.0 (WAN)
LAN B is 10.0.0.0

[Jonathan L]

LAN A is 192.168.1.0 (WAN)
LAN B is 10.0.0.0

Hi ..

(192.168.1.1: sorry. I did misread it.)

Are you quite certain you're getting any packets at all out of the LAN B? Would you post the results of

ifconfig
netstat -rn
ping -w 2 10.0.0.thisbox
ping -w 2 192.168.1.thisbox

(for thisbox use the machine's own numbers).

What you've described is completely sensible: I'd be double checking the obvious things.

Kind regards,
Jonathan.

[cogitordi]

netstat -rn

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.0.0.0        0.0.0.0         255.255.255.0   U         0 0          0 eth1
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 eth1
0.0.0.0         192.168.1.1     0.0.0.0         UG        0 0          0 eth0

ping -w 2 10.0.0.31

PING 10.0.0.31 (10.0.0.31) 56(84) bytes of data.
64 bytes from 10.0.0.31: icmp_seq=1 ttl=64 time=0.058 ms
64 bytes from 10.0.0.31: icmp_seq=2 ttl=64 time=0.050 ms
64 bytes from 10.0.0.31: icmp_seq=3 ttl=64 time=0.045 ms

--- 10.0.0.31 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1998ms
rtt min/avg/max/mdev = 0.045/0.051/0.058/0.005 ms

ping -w 2 192.168.1.17
PING 192.168.1.17 (192.168.1.17) 56(84) bytes of data.
64 bytes from 192.168.1.17: icmp_seq=1 ttl=64 time=0.058 ms
64 bytes from 192.168.1.17: icmp_seq=2 ttl=64 time=0.053 ms
64 bytes from 192.168.1.17: icmp_seq=3 ttl=64 time=0.047 ms

--- 192.168.1.17 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1998ms
rtt min/avg/max/mdev = 0.047/0.052/0.058/0.009 ms

ifconfig

eth0      Link encap:Ethernet  HWaddr 00:16:17:92:36:09  
          inet addr:192.168.1.17  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::216:17ff:fe92:3609/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7856 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6853 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:6391986 (6.3 MB)  TX bytes:1057778 (1.0 MB)
          Interrupt:16 

eth1      Link encap:Ethernet  HWaddr 00:16:17:92:35:19  
          inet addr:10.0.0.31  Bcast:10.0.0.255  Mask:255.255.255.0
          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:23 Base address:0xa000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:22 errors:0 dropped:0 overruns:0 frame:0
          TX packets:22 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:1712 (1.7 KB)  TX bytes:1712 (1.7 KB)

[Jonathan L]

eth1      Link encap:Ethernet  HWaddr 00:16:17:92:35:19  
          inet addr:10.0.0.31  Bcast:10.0.0.255  Mask:255.255.255.0
          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:23 Base address:0xa000

Hi

All that looks exactly how it should be done: except we see the RX and RX packet counts are zero. Unless everything else was switched off, I am suspecting your cable or your switch. I'd run tcpdump to see if there is anything at to be seen (should see at least arp when the other things talk, and NAS units tend to do a lot of netbios broadcasts):

sudo tcpdump -i eth1 -n

And I'd check the cables and switch.

Hope that helps.

Kind regards,
Jonathan.

[cogitordi]

All that looks exactly how it should be done: except we see the RX and RX packet counts are zero. Unless everything else was switched off, I am suspecting your cable or your switch.

Yes, no packet counts. I have an M-Windows box connected to both networks and it is working correctly. I can see all the devices from it. So, my routers and switches are working.

I have connected a known good cable. After more fiddling, I can ping both routers but the default gateway is set to Router B (Network B) instead of Router A. I need to research the command to correct this. IP ROUTE something or other...

I am wondering if some of the problem is due to the drivers for my NVidia and Marvell ethernet ports. I suppose one way to confirm this would be to (yuck) install Windows. (o;

[Jonathan L]

Yes, no packet counts. I have an M-Windows box connected to both networks and it is working correctly. I can see all the devices from it. So, my routers and switches are working.

I have connected a known good cable. After more fiddling, I can ping both routers but the default gateway is set to Router B (Network B) instead of Router A. I need to research the command to correct this. IP ROUTE something or other...

I am wondering if some of the problem is due to the drivers for my NVidia and Marvell ethernet ports. I suppose one way to confirm this would be to (yuck) install Windows. (o;

Glad you've got them pinging. If the default route is set to B, my guess is that the DHCP is doing that, and you'd be better off disabling it or putting a static route there.

What kind of "more fiddling" did you do to get them pinging? Did you get any luck with the tcpdump I suggested? Known good cable: but did you try a known good socket on the router?

Just some thoughts.

Kind regards
Jonathan.