[NBLUG/talk] Difficult Network problem

[Mansur, Warren]

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I can ping each interface (192.168.1.1 and 192.168.1.2) but only one interface will work at one time.
Server # route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
nas1.sr2.sonic. *               255.255.255.255 UH    0      0        0 ppp0
192.168.1.0     *               255.255.255.224 U     0      0        0 eth0
192.168.1.0     *               255.255.255.224 U     0      0        0 eth1
loopback        localhost       255.0.0.0       UG    0      0        0 lo
default         nas1.sr2.sonic. 0.0.0.0         UG    0      0        0 ppp0
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>From what IP address are you pinging the interfaces?

In the routing table, you will see that both eth0 and eth1 claim to be able to acesss 192.168.1.0/255.255.255.224. The second entry in the routing table is ignored because only the first one that matches will be used. The routing table indicates that eth0 and eth1 can access all the same machines. Is that true?

Ping works by sending a query and getting a response. If you ping eth1 from a machine with an address 192.168.1.xxx, then the response will _not_ go out eth1. The response will go out eth0. Again, this is because first entry that matches in the routing table is eth0 and that first entry will be used.

So what may be happening is, all the responses to the ping are going out eth0 instead of eth1. If eth0 and eth1 are really on the same network, as the routing table indicates, it would still work correctly. However, if eth0 and eth1 are on different networks, then all of the responses will be lost. In that case eth0 and eth1 should be on different subnets (for example 192.168.1.xxx 192.168.2.xxx).

Cheers,

Warren

-----Original Message-----
From: talk-bounces at nblug.org [mailto:talk-bounces at nblug.org] On Behalf Of ShadowEyez
Sent: Wednesday, September 22, 2004 7:51 PM
To: talk at nblug.org
Subject: [NBLUG/talk] Difficult Network problem

Odd networking problem with Gentoo Linux 2004.2, 2.6.7, i586, stage3 install
There are 3 network interfaces, a modem (ppp0, on /dev/ttyS4), and two 10 mbit ethernet nics (eth0 and eth1) .  They are the same type of nics with the driver loaded into the kernel (NE-2000 realteks but they have different layer 2 MAC addresses), and the /etc/conf.d/net file has the lines:
iface_eth0="192.168.1.1 broadcast 192.168.1.31 netmask 255.255.255.224"
iface_eth1="192.168.1.2 broadcast 192.168.1.31 netmask 255.255.255.224"
that I set up, meaning all the ip info is right, problem is I can only get one of the interfaces to work at the same time!
 
I can ping each interface (192.168.1.1 and 192.168.1.2) but only one interface will work at one time.  I know the hardware and ip address are right because when I run
ifconfig eth0 down && ifconfig eth1 up
I can plug a working device into eth1 and it works.
ifconfig eth1 down && ifconfig eth0 up
I plug a working device into eth0 and it works, but when both are up THEY DO NOT WORK AT THE SAME TIME.
The ppp0 interface (modem) is set to be the default route, and adjusting the routing table does no good.  Output of the route command:
Server # route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
nas1.sr2.sonic. *               255.255.255.255 UH    0      0        0 ppp0
192.168.1.0     *               255.255.255.224 U     0      0        0 eth0
192.168.1.0     *               255.255.255.224 U     0      0        0 eth1
loopback        localhost       255.0.0.0       UG    0      0        0 lo
default         nas1.sr2.sonic. 0.0.0.0         UG    0      0        0 ppp0
The command ifconfig gives:
Server # ifconfig
eth0      Link encap:Ethernet  HWaddr 00:C0:0C:B0:57:11  
          inet addr:192.168.1.1  Bcast:192.168.1.31  Mask:255.255.255.224
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8847 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8294 errors:0 dropped:0 overruns:0 carrier:0
          collisions:3 txqueuelen:1000 
          RX bytes:1680159 (1.6 Mb)  TX bytes:5589375 (5.3 Mb)
          Interrupt:15 Base address:0xb800 
 
eth1      Link encap:Ethernet  HWaddr 00:C0:0C:B0:55:1B  
          inet addr:192.168.1.2  Bcast:192.168.1.31  Mask:255.255.255.224
          UP BROADCAST RUNNING 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:12 Base address:0xb400 
 
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:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
 
ppp0      Link encap:Point-to-Point Protocol  
          inet addr:209.148.104.235  P-t-P:209.204.168.83  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1514  Metric:1
          RX packets:7830 errors:1 dropped:0 overruns:0 frame:0
          TX packets:8392 errors:0 dropped:12 overruns:0 carrier:0
          collisions:0 txqueuelen:3 
          RX bytes:5422514 (5.1 Mb)  TX bytes:1408388 (1.3 Mb)
Again, though I can ping the eth1 interface, nothing plugged into it will work.  All cables and cards are plugged in and working.  How do I get both ethernet interfaces working?
 
TIA
ShadowEyez