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. <div><br></div>
<div>The <span class="Apple-style-span" style="font-family: 'courier new', monospace;">/etc/network/interfaces</span> file is as under:</div><div><br></div><div><div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;">auto lo</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;">iface lo inet loopback</span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"><br>
</span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;">auto eth0</span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;">iface eth0 inet static</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> address 10.19.175.242</span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> netmask 255.255.255.240</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> network 10.19.175.240</span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> broadcast 10.19.175.255</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> gateway 10.19.175.241</span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> dns-nameservers 10.19.173.245</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"><br></span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;">auto eth1</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;">iface eth1 inet static</span></div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> address 192.168.164.2</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"> netmask 255.255.252.0</span></div><div><br></div></div><div>The output of <span class="Apple-style-span" style="font-family: 'courier new', monospace;">netstat -nr</span> is as under:</div>
<div><span class="Apple-style-span" style="font-family: 'courier new', monospace;"><br></span></div><div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">Kernel IP routing table</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">Destination Gateway Genmask Flags MSS Window irtt Iface</span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">10.19.175.240 0.0.0.0 255.255.255.240 U 0 0 0 eth0</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">192.168.164.0 0.0.0.0 255.255.252.0 U 0 0 0 eth1</span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1</span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">0.0.0.0 10.19.175.241 0.0.0.0 UG 0 0 0 eth0</span></div><div><br></div><div><br></div><div>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. </div>
<div><br></div><div>If I were to do:</div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;"><br></span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">$ sudo route delete default device eth0<br>
</span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">$ sudo route add default gw 192.168.164.1 device eth1 </span><br></div><div><br></div><div>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. </div>
<div><br></div><div><br></div><div>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:</div>
<div><span class="Apple-style-span" style="font-family: 'courier new', monospace;"><br></span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;"># route delete default device eth1<br>
</span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;"># route add default gw 10.19.175.241 device eth0</span></div><div><br></div><div>and the routing table:</div><div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"><br>
</span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">[root@localhost ~]# route </span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">Kernel IP routing table </span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">Destination Gateway Genmask Flags Metric Ref Use Iface</span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">10.19.175.240 * 255.255.255.240 U 1 0 0 eth0 </span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">192.168.164.0 * 255.255.252.0 U 1 0 0 eth1 </span></div><div><span class="Apple-style-span" style="font-family: 'courier new', monospace;">default 10.19.175.241 0.0.0.0 UG 0 0 0 eth0 </span></div>
<div><span class="Apple-style-span" style="font-family: 'courier new'; font-size: 12px;"><br></span></div><div><span class="Apple-style-span" style="font-size: 12px; "><span class="Apple-style-span" style="font-family: arial, helvetica, sans-serif;">And I was able to reach both the eth0 and eth1 interfaces at this point from appropriate machines on the network.</span></span></div>
<div> <br></div><div>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. </div>
<div><br></div><div>Any idea why Ubuntu would behave differently? I'd appreciate any suggestions on what I could try so that both interfaces are reachable simultaneously.</div><div><br></div><div>Thanks,</div><div>Venkat. <br>
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