VMWARE Linux – Adding a Second NIC for a Guest Linux VM – With No Service Disruption
This is post is to explain the configuration of a linux VM with a secondary NIC without reboot or restart network services. This is fairly simple and straight forward task, but I am just posting it for the folks who are new for the Linux VM on Vmware.
Unlike physical systems you don’t need to shutdown the box to add new physical NIC card ( just in case if you don’t have enough on board interface) . Once the VMWARE engineer creates a Virtual NIC on Hypervisor and attach it to our system, linux will automatically recognize the new device and will show you in the ifconfig output.
In the blow example, the scenario is we are actually configuring a secondary interface and attaching a network IP to it, and then we are adding additional static routes for the secondary IP.
Below is the Initial configuration, before detecting the new NIC port:
[root@gurkullinuxVM ~]# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:50:56:20:26:24
inet addr:199.9.200.101 Bcast:14.129.48.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:224666676 errors:0 dropped:0 overruns:0 frame:0
TX packets:161900293 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:5000
RX bytes:41534486993 (38.6 GiB) TX bytes:145549058043 (135.5 GiB)
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:163605347 errors:0 dropped:0 overruns:0 frame:0
TX packets:163605347 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2256211008871 (2.0 TiB) TX bytes:2256211008871 (2.0 TiB)
Below is the original Static route configuration before adding additional routes
# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
100.10.103.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
199.9.200.101 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 199.9.200.1 0.0.0.0 UG 0 0 0 eth0
Current eth0 configuration file as below
$ cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=static
IPADDR=199.9.200.101
NETMASK=255.255.255.0
ONBOOT=yes
$
And once the VMWare engineer configures the additional nic for the linux box, the nic port will be automatically visible in the system. And you can see eth1 in the below ifconfig output
[root@gurkullinuxVM ~]# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:ab:56:20:26:24
inet addr:199.9.200.101Bcast:14.129.48.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:225650315 errors:0 dropped:0 overruns:0 frame:0
TX packets:162774611 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:5000
RX bytes:39536609117 (36.8 GiB) TX bytes:146395475846 (136.3 GiB)
eth1 Link encap:Ethernet HWaddr 00:ab:56:9C:2A:FC
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)
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:163611622 errors:0 dropped:0 overruns:0 frame:0
TX packets:163611622 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2256212079066 (2.0 TiB) TX bytes:2256212079066 (2.0 TiB)
Then we have create a new ethernet configuration file for the eth1 as below
$ cat ifcfg-eth1
DEVICE=eth1
BOOTPROTO=static
IPADDR=100.10.103.71
NETMASK=255.255.255.0
ONBOOT=yes
TYPE=Ethernet
Before you bring up the additional NIC just test for link connection using the ethtool as below
[root@gurkullinuxVM network-scripts]# ethtool eth1
Settings for eth1:
Supported ports: [ TP ]
Supported link modes: 1000baseT/Full
10000baseT/Full
Supports auto-negotiation: No
Advertised link modes: Not reported
Advertised auto-negotiation: No
Speed: 10000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 0
Transceiver: internal
Auto-negotiation: off
Supports Wake-on: uag
Wake-on: d
Link detected: yes
And once we know the interface is available and the “Link Detected = yes”, we can bring up the additional interface using the configuration we entered in “/etc/sysconfig/network-scripts/ifcfg-eth1″ , using the below command.
# ifup eth1
Setting ringbuffer settings to maximum for eth1
Increasing txqueuelen for eth1 (from 1000 to 5000)
then we can check the new configuration from the ifconfig output as below
[root@gurkullinuxVM network-scripts]# ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:ab:56:20:26:24
inet addr:199.9.200.101 Bcast:14.129.48.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:226458330 errors:0 dropped:0 overruns:0 frame:0
TX packets:163348262 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:5000
RX bytes:39708756293 (36.9 GiB) TX bytes:147033108626 (136.9 GiB)
eth1 Link encap:Ethernet HWaddr 00:ab:56:9C:2A:FC
inet addr:100.10.103.71 Bcast:100.10.103.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:735 errors:0 dropped:0 overruns:0 frame:0
TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:5000
RX bytes:49548 (48.3 KiB) TX bytes:1120 (1.0 KiB)
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:163619066 errors:0 dropped:0 overruns:0 frame:0
TX packets:163619066 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2256213415106 (2.0 TiB) TX bytes:2256213415106 (2.0 TiB)
Now the second task is additing static routes for the new IP connection ( i.e. eth1). For that purpose we have to configure the file “/etc/sysconfig/network-scripts/route-eth1″ as shown below. And each entry talks about one route.
Entry format :
<Destination Network address >/ <Desitnation Subnetmask > via <Gateway> dev <network interface>
$ cat route-eth1
100.10.101.0/24 via 100.10.103.1 dev eth1
100.10.102.0/24 via 100.10.103.1 dev eth1
100.10.103.0/24 via 100.10.103.1 dev eth1
100.10.104.0/24 via 100.10.103.1 dev eth1
Once you have the static route information ready in the file “route-eth1″, you just have to make them active using the below command. Please note that in the below command I am just using the eth1 , which doesn’t affect the existing interface.
# ./ifup-routes eth1
Now you can check the new route configuration with netstat command as given below:
$ netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
100.10.101.0 100.10.103.1 255.255.255.0 UG 0 0 0 eth1
100.10.103.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
100.10.102.0 100.10.103.1 255.255.255.0 UG 0 0 0 eth1
199.9.200.101 0.0.0.0 255.255.255.0 U 0 0 0 eth0
100.10.104.0 100.10.103.1 255.255.255.0 UG 0 0 0 eth1
0.0.0.0 199.9.200.1 0.0.0.0 UG 0 0 0 eth0
$
That’s it for the day
