Multiple network interfaces in debian w/ sporadic connection

JohnLocke · 09-06-2013, 12:25 AM

I've got a Raspberry Pi running Raspbian (wheezy). I'm working on it to have three network connections ... the ethernet connection and two wireless connections from usb dongles.

So far, I set it up so that any one of them works correctly. Any two of them will act like they're configuring, but if I "ifdown" the primary connection, I'm off the network.

What I want to happen is that all three are connected, and I'm able to bring down any two of them and the other still functions. These may or may not be on the same network (in the end, I'm going to be using just the wireless networks, but will need the ethernet network for initial configuration).

Currently, when I do a networking restart, I get:
SIOCDELRT: No such process

But it appears to configure.

The bigger problem is that when I do an "ifdown eth0", I'm still on the network (I can ping other boxes on the network), but my gateway appears to be gone (I can't ping google.com or 8.8.8.8) ... I get "Network is unreachable". I also get that same error when I execute the ifdown command. So it's finding something it doesn't like. messages doesn't have any information, though.

I've tried this with both dchp and static IP's, so I'm not quite sure what I'm messing up here. I thought dhcp would at least work.

Here's my interfaces file:

Code:

auto lo

iface lo inet loopback

######################
### LAN config
######################

auto eth0
        # if using DCHP
     #iface eth0 inet dhcp
 
        # if using static IP
     iface eth0 inet static
     address 192.168.1.50
     post-up route add default gw 192.168.1.1 metric 1
     post-down route del default gw 192.168.1.1 metric 1
     netmask 255.255.255.0
     network 192.168.1.0
     broadcast 192.168.1.255
     dns-nameservers 192.168.1.1 8.8.8.8

######################
### Wireless config
######################

auto wlan0
        # If using DHCP
     #iface wlan0 inet dhcp

        # If using static IP
     iface wlan0 inet static
     address 192.168.1.51
     post-up route add default gw 192.168.1.1 metric 2
     post-down route del default gw 192.168.1.1 metric 2
     netmask 255.255.255.0
     network 192.168.1.0
     broadcast 192.168.1.255
     dns-nameservers 192.168.1.1 8.8.8.8

        # wpa and wpa2
     wpa-ssid Firefly
     wpa-psk <my key>

#auto wlan1
        # If using DHCP
     #iface wlan1 inet dhcp

        # If using static IP
     iface wlan1 inet static
     address 192.168.1.52
     post-up route add default gw 192.168.1.1 metric 3
     post-down route del default gw 192.168.1.1 metric 3
     netmask 255.255.255.0
     network 192.168.1.0
     broadcast 192.168.1.255
     dns-nameservers 192.168.1.1 8.8.8.8

        # wpa and wpa2
     wpa-ssid Serenity
     wpa-psk <my key>

Here's my ifconfig when both eth0 and wlan0 are up (I haven't done it with all three yet because 1) I have problems with just two and 2) I need one of the usb slots for my keyboard while I'm messing with the network ... hard to ssh in with no network).

Code:

eth0      Link encap:Ethernet  HWaddr b8:27:eb:d4:00:99  
          inet addr:192.168.1.50  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3545 errors:0 dropped:25 overruns:0 frame:0
          TX packets:597 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:409262 (399.6 KiB)  TX bytes:55618 (54.3 KiB)

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:54 errors:0 dropped:0 overruns:0 frame:0
          TX packets:54 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:5376 (5.2 KiB)  TX bytes:5376 (5.2 KiB)

wlan0     Link encap:Ethernet  HWaddr c8:3a:35:cb:19:4b  
          inet addr:192.168.1.51  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2355 errors:0 dropped:0 overruns:0 frame:0
          TX packets:398 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:347234 (339.0 KiB)  TX bytes:48394 (47.2 KiB)

And my hosts file

Code:

127.0.0.1	localhost
::1		localhost ip6-localhost ip6-loopback
fe00::0		ip6-localnet
ff00::0		ip6-mcastprefix
ff02::1		ip6-allnodes
ff02::2		ip6-allrouters

127.0.1.1	raspberrypi

192.168.1.50	raspberrypi
192.168.1.51	raspberrypi
192.168.1.52	raspberrypi

Any idea what I'm missing?

nini09 · 09-06-2013, 03:29 PM

The problem is default route. If you want to use multi default routes, multi route tables have to be created.

dkm999 · 09-16-2013, 02:14 PM

To expand on nini09's reply, Linux network configuration only knows how to declare a single default route (this rule says "send all packets that aren't otherwise matched in my routing table through interface xxx"). In order to solve the problem you are trying to solve, you will have to manage that default route somehow as each interface goes down or comes up.

There are a variety of ways of doing this, none perfect. But the easiest way is to run a routing daemon. The traditional one is called routed, but there are several others that you can find on the Internet.

Hope this helps.

JohnLocke · 09-16-2013, 02:19 PM

Realized I hadn't replied yet, but just wanted to say thanks for both answers!

lleb · 09-16-2013, 02:25 PM

one more thing to keep in mind for you RPi, make sure you are using a stronger then 1A power supply. if you are trying to power 2 WiFi adapters via USB, Id have nothing less then a 2A psu.