Ubuntu: Only one of my two network cards is working



Question:

I have a Ubuntu 10.04 LTS Server which has two Ethernet ports eth0 and eth1.

  • eth0 is connected to ISP1 with network 192.168.3.0/24 with server static address 192.168.3. 5

  • eth1 is connected to ISP2 with network 192.168.5.0/24 with server static address 192.168.5.10

When eth1 is connected, there is no internet connection from eth0. The internal network is accessible, eg, ssh , ping from other computers in 192.168.3.0/24 network.

When eth1 is disabled or disconnected, eth0 works just fine.

How can I ensure that both the Ethernet ports get internet connections?

netstat configs eth1 disabled

Kernel IP routing table    Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface    192.168.3.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0    0.0.0.0         192.168.3.1     0.0.0.0         UG        0 0          0 eth0  

Netstat config eth1 enabled

Kernel IP routing table    Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface    192.168.3.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0    192.168.5.0     0.0.0.0         255.255.255.0   U         0 0          0 eth1    0.0.0.0         192.168.5.254   0.0.0.0         UG        0 0          0 eth1    0.0.0.0         192.168.3.1     0.0.0.0         UG        0 0          0 eth0  

Edit

I have also checked /etc/resolv.conf

There, I have manually added the nameserver for both the gateways.

ip addr show

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN       link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00      inet 127.0.0.1/8 scope host lo      inet6 ::1/128 scope host          valid_lft forever preferred_lft forever  2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000      link/ether 11:bb:3e:15:3e:0e brd ff:ff:ff:ff:ff:ff      inet 192.168.3.100/24 brd 192.168.3.255 scope global eth0             valid_lft forever preferred_lft forever  3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 100      link/ether aa:2a:ae:5f:59:e8 brd ff:ff:ff:ff:ff:ff      inet 192.168.5.100/24 brd 192.168.5.255 scope global eth1             valid_lft forever preferred_lft forever  


Solution:1

I made a possible running example based on the basic implementation (of Split access) taken from here.

Create two additional routing tables, say T1 and T2.

ip route add 192.168.3.0/24 dev eth0 src 192.168.3.5 table T1  ip route add default via 192.168.3.0/24 table T1  ip route add 192.168.5.0/24 dev eth1 src 192.168.5.10 table T2  ip route add default via 192.168.5.0/24 table T2  

Set up the main routing table:

ip route add 192.168.3.0/24 dev eth0 src 192.168.3.5  ip route add 192.168.5.0/24 dev eth1 src 192.168.5.10  

Add your preference for default route:

ip route add default via 192.168.3.5  

Set up the routing rules, choose what routing table to route with.

ip rule add from 192.168.3.5 table T1  ip rule add from 192.168.5.10 table T2  

More info here.


Solution:2

Check out that both ports are up. Reconfigure eth1, eth0 as always up.


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