One of the applications that I am working with requires a fairly unorthodox
network configuration. This machine is running Ubuntu 8.10 with all the
latest patches. This has multiple wired network interfaces.
The /etc/network/interfaces file is as under:
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address 10.19.175.242
netmask 255.255.255.240
network 10.19.175.240
broadcast 10.19.175.255
gateway 10.19.175.241
dns-nameservers 10.19.173.245
auto eth1
iface eth1 inet static
address 192.168.164.2
netmask 255.255.252.0
The output of netstat -nr is as under:
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt
Iface
10.19.175.240 0.0.0.0 255.255.255.240 U 0 0 0
eth0
192.168.164.0 0.0.0.0 255.255.252.0 U 0 0 0
eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0
eth1
0.0.0.0 10.19.175.241 0.0.0.0 UG 0 0 0
eth0
The network cables from these two interfaces terminate on a Cisco 6509
switch. Another machine of interest is also connected to this switch. Pings
from this other machine to the 192.168.164.2 interface are not returned.
If I were to do:
$ sudo route delete default device eth0
$ sudo route add default gw 192.168.164.1 device eth1
then the other machine is able to ping 192.168.164.2. Of course I lose the
ability to reach the 10.19.175.242 interface.
I tried the Fedora 10 Live distribution on the same machine. I used the
NetworkManager applet to first configure eth0, checked the connectivity to
that interface before configuring the eth1 interface. I lost connectivity to
the eth0 interface at this point. I then did the following:
# route delete default device eth1
# route add default gw 10.19.175.241 device eth0
and the routing table:
[root at localhost ~]# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
10.19.175.240 * 255.255.255.240 U 1 0 0
eth0
192.168.164.0 * 255.255.252.0 U 1 0 0
eth1
default 10.19.175.241 0.0.0.0 UG 0 0 0
eth0
And I was able to reach both the eth0 and eth1 interfaces at this point from
appropriate machines on the network.
I tried using a bootable USB Live Ubuntu 8.10, and I repeated the exact
steps I had performed with the F10 and I was only able to reach one of the
interfaces and not both at the same time. I can run tcpdump on the
interfaces separately and I can see ICMP Requests coming in on both the
interfaces but only one of the interfaces responds with an ICMP Reply.
Any idea why Ubuntu would behave differently? I'd appreciate any suggestions
on what I could try so that both interfaces are reachable simultaneously.
Thanks,
Venkat.
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