eth0(WAN) and eth1(LAN) getting mixed with weird results

Artanicus · 08-12-2005, 06:25 AM

The prblem itself:
Azureus is moving data at 50kbps/50kbps (so moving both up- and downstream) thru the dedicated WAN intrface. Or atleast it should.. (; Instead, the upstream traffic is routed thru eth1 that is a didicated LAN interface (according to both iptraf and gkrellm). I didnt notice the problem until today, possibly due to that an LTSP terminal was active, effectively hiding any excess upstream counted for the wrong interface, so it is possible that this has been going on since the firewall modifications. (See history below)

This situation doesnt cause any discomfort except making monitoring a tad paining of a task, but moreof causes extremem bewilderment as to why is the data going upstream through an interface that doesnt have a WAN ip. (only LAN, see ifconfig appendice)

_Any_ ideas or theories are welcome, this one realy caught me by surprise.. Ive got no idea of whats going on.. (:

History:
I have a rather unusual network topography at home, well atleast unusual to other solutions ive encountered. All the machines on the network have a public ip address, plus a LAN address in the 192.168.0.x address space. The simple reason is that I hate NAT, and would need a seperate unit for it due to ISP restrictions on the modem.

So, recently I upgraded my personal iptables firewall (on the machine called indigo that is the object of this abnormality) with fwbuilder, and encountered serious problems with my habit of using virtual (eth0:0) interfaces for the LAN. Fwbuilder handles virtual interfaces as a part of the main interface, and having an interface set up with a dynamic ip plus a static LAN ip was impossible, even though the virtyualization made it possible with ifconfig, but iptables didnt like this at all. So, as a remedy I hooked up the second port of the integrated NIC to the same switch the mahine was on, now with two identical connections. Thus having seperated the LAN over to eth1, fwbuilder was happy and joy ensued. Untill this weirdness arose.

versions / appendices:
Slackware Linux current (== 10.2)
Linux 2.4.31
Iptables 1.3.3

ifconfig quote (censored):

Code:

eth0      Link encap:Ethernet  HWaddr 00:11:22:33:44:55  
          inet addr:xxx.xxx.xxx.xxx  Bcast:xxx.xxx.xxx.xxx  Mask:255.255.240.0
          UP BROADCAST NOTRAILERS RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:11063177 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11809020 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3209599625 (3060.9 Mb)  TX bytes:2443151044 (2329.9 Mb)
          Interrupt:11 Base address:0x9000 

eth1      Link encap:Ethernet  HWaddr 66:77:88:99:00:11  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:23685139 errors:1 dropped:0 overruns:0 frame:1
          TX packets:35503945 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1540653708 (1469.2 Mb)  TX bytes:2596033806 (2475.7 Mb)
          Interrupt:5 Base address:0x1000 

eth1:FWB1 Link encap:Ethernet  HWaddr 66:77:88:99:00:11
          inet addr:192.168.0.5  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:5 Base address:0x1000 

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:55365 errors:0 dropped:0 overruns:0 frame:0
          TX packets:55365 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:6588298 (6.2 Mb)  TX bytes:6588298 (6.2 Mb)

vmnet1    Link encap:Ethernet  HWaddr 22:33:44:55:66:77  
          inet addr:172.16.75.1  Bcast:172.16.75.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:9 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)

Xing · 08-12-2005, 06:34 AM

Have you tried using 'route'.. check man route for more info..

Artanicus · 08-12-2005, 07:01 AM

routing has allways been abit of mystery to me, so I havnt myself modified them at all, but heres the output if its of any worth:

Code:

# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1
172.16.75.0     0.0.0.0         255.255.255.0   U     0      0        0 vmnet1
xxx.xxx.xxx.0    0.0.0.0         255.255.240.0   U     0      0        0 eth0
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
0.0.0.0         xxx.xxx.xxx.1    0.0.0.0         UG    0      0        0 eth0

Artanicus · 08-12-2005, 07:23 AM

Update:
Well, all of a sudden, when I wasnt looking, everything returned to normal.. All the traffic is again going through eth0 (both gkrellm and iptraf agree on this)...

/me is even more confuzzled.

Even more now this demands for a rational explenation.. Oh yeah, I checked, there was no assigned traffic for LAN, no one else is online, and both of the ports were flashing lights (transfer) so this wasnt just an error in monitoring.. And yeah, the lan light now has gone back to sleep..