Linux – Second network card configuration not working

centos5linuxnetworking

I have 4 servers running Centos 5. All of them have two ethernet network cards.

I have configured 192.168.1.x IP addresses on their eth0 card. They are all connected to the same switch using their eth0 card and they are all working.

I have configured 10.72.11.x IP addresses on their eth1 card.They are all connected to the same switch – a different one from the switch used with eth0 card – using their eth1 card and they are NOT all working.

Their configuration files is like:

DEVICE=eth1
BOOTPROTO=static
IPADDR=10.72.11.236
BROADCAST=10.72.11.191
NETMASK=255.255.255.192
NETWORK=10.72.11.128
HWADDR=84:2B:2B:55:4B:98
IPV6INIT=yes
IPV6_AUTOCONF=yes
ONBOOT=yes

The interface is starting and configured as I need.

[root@sql1 network-scripts]# ifconfig
**eth0**  Link encap:Ethernet  HWaddr 84:2B:2B:55:4B:97
          inet addr:192.168.1.105  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::862b:2bff:fe55:4b97/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2981 errors:0 dropped:0 overruns:0 frame:0
          TX packets:319 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:386809 (377.7 KiB)  TX bytes:66134 (64.5 KiB)
          Interrupt:36 Memory:da000000-da012800

**eth1**  Link encap:Ethernet  HWaddr 84:2B:2B:55:4B:98
          inet addr:10.72.11.236  Bcast:10.72.11.191  Mask:255.255.255.192
          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:48 Memory:dc000000-dc012800

I also added a route-eth1 file that looks like:

10.0.0.0/8 via 10.72.11.254

Routing looks fine to me:

[root@sql1 network-scripts]# netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.72.11.192    0.0.0.0         255.255.255.192 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
10.0.0.0        10.72.11.254    255.0.0.0       UG        0 0          0 eth1
0.0.0.0         192.168.1.1     0.0.0.0         UG        0 0          0 eth0

But I cannot ping one server from the other.

[root@sql1 network-scripts]# ping 10.72.11.235
PING 10.72.11.235 (10.72.11.235) 56(84) bytes of data.
From 10.72.11.236 icmp_seq=1 Destination Host Unreachable
From 10.72.11.236 icmp_seq=2 Destination Host Unreachable
From 10.72.11.236 icmp_seq=3 Destination Host Unreachable
From 10.72.11.236 icmp_seq=4 Destination Host Unreachable
From 10.72.11.236 icmp_seq=5 Destination Host Unreachable
From 10.72.11.236 icmp_seq=6 Destination Host Unreachable
^C
--- 10.72.11.235 ping statistics ---
7 packets transmitted, 0 received, +6 errors, 100% packet loss, time 6033ms, pipe 3

What am I doing wrong?

Best Answer

It should be noted that your NICs aren't properly 'working'. Your ifconfig output doesn't show the 'RUNNING' required for there to be a properly working link. note the line UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 from your eth0 interface. There's no 'RUNNING' evident in the eth1 output. In my experience, this indicates a low level issue. eg: Bad/disconnected cabling.

Is is possible the NIC you have plugged your cable into is NOT eth1? Servers can get some weird naming going on. Try checking the output of /var/log/messages, to see if it reports an interface getting (dis)connected. Likewise, see if you get any diagnostic info there when you connect/disconnect, or during boot. Check and see if this is occurring on all 5 boxes. You may also want to try the graphical configuration tool, just in case you've got a typo in the configuration file. (system-config-network)

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