NOTE: The information in this section is based on information from the vendors of these servers. For more information, please consult your real server vendor.
Solaris
To configure a loopback address on Solaris, enter the following command: ifconfig lo0:1 <vip-addr> netmask <net-mask> up
You might need to “plumb” the interface first. In this case, enter the following commands: ifconfig lo0:1 plumb
ifconfig lo0:1 <vip-addr> netmask <net-mask> up
NOTE: This command applies to the current running configuration only. To make the address permanent so that it is reconfigured following a reboot or power cycle, create the file /etc/hostname.lo0:1.
NOTE: For Hewlett-Packard (HP) version 11.x, use the May 2000 or later patch.
Linux
To configure a loopback interface on Linux, enter a command such as the following: ifconfig lo:0 <vip-addr> netmask <net-mask> up
NOTE: This command applies to the current running configuration only. To make the address permanent so that it is reconfigured following a reboot or power cycle, go to /etc/sysconfig/network-scripts and make a file called ifcfg-lo:0 using ifcfg-lo as a template.
NT
To configure a loopback interface on NT, you need to configure a new network adapter. Use the following procedure. This procedure applies to the following products:
• Microsoft Windows 2000 Professional • Microsoft Windows 2000 Server
• Microsoft Windows 2000 Advanced Server • Microsoft Windows 2000 Datacenter Server
NOTE: When you add a loopback interface to NT, NT sometimes creates a route that has the same address as the loopback interface. You need to delete this route. In come cases, the procedure for deleting the route can include deleting the correct route to the server’s default gateway. When this is the case, you need to add this route back to NT.
Manual Installation
1. Click Start, point to Settings, click Control Panel, and then double-click Add/Remove Hardware. 2. Click Add/Troubleshoot a device, and then click Next.
3. Click Add a new device, and then click Next.
4. Click No, I want to select the hardware from a list, and then click Next. 5. Click Network adapters, and then click Next.
6. In the Manufacturers box, click Microsoft.
7. In the Network Adapter box, click Microsoft Loopback Adapter, and then click Next. 8. Click Finish.
After the adapter is installed successfully, you can configure its options manually, as with any other adapter. NOTE: If the TCP/IP properties are configured to use DHCP (the default), the adapter will eventually use an autonet address (169.254.x.x/16) because it is not actually connected to any physical media.
Unattended Installation
Modify the Unattend.txt file using the following example as a guide to install the Microsoft Loopback adapter:
[NetAdapters]
Adapter01=Params.Adapter01 [Params.Adapter01]
InfID="*msloop" ; Microsoft Loopback Adapter ConnectionName = "MS Loopback Adapter" [NetProtocols]
MS_TCPIP=Params.MS_TCPIP ; TCP/IP parameters
; Use parameter values specific to your network [Params.MS_TCPIP]
AdapterSections=params.TCPIP.Adapter01 DNS=yes
DNSSuffixSearchOrder=mycorp.com EnableLMHosts=No
; Adapter Specific TCP/IP parameters
; Use parameter values specific to your network [params.TCPIP.Adapter01] SpecificTo=Adapter01 DNSDomain=mycorp.com DNSServerSearchOrder=192.168.5.251 WINS=no DHCP=no IPAddress=192.168.5.10 SubnetMask=255.255.255.0 DefaultGateway=192.168.5.254
Deleting the Unwanted Routes
In some cases, NT creates a route that has the same address as the loopback interface. You need to delete this route.
Two methods are shown in this section. If you receive an error message while trying to use the simple method, you need to use the long method instead.
NOTE: Regardless of the method you use, you must repeat the procedure every time the NT server is booted. However, you can create a small batch file to enter these commands and add the batch file to the AT subsystem so that the file runs automatically each time the server is booted.
Simple Method
The simple method requires you to delete the route that NT creates when you add the loopback interface. The route you need to delete is the one that has the same IP address as the loopback interface.
1. Enter the route print command to display the server’s route table. In this example, the loopback interface has address 192.168.200.106.
C:\>route print Active Routes:
Network Address Netmask Gateway Address Interface Metric 0.0.0.0 0.0.0.0 192.168.204.254 192.168.200.251 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.200.0 255.255.255.0 192.168.200.106 192.168.200.106 1 192.168.200.0 255.255.255.0 192.168.200.251 192.168.200.251 1 192.168.200.106 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.251 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.255 255.255.255.255 192.168.200.251 192.168.200.251 1 224.0.0.0 224.0.0.0 192.168.200.106 192.168.200.106 1 224.0.0.0 224.0.0.0 192.168.200.251 192.168.200.251 1 255.255.255.255 255.255.255.255 192.168.200.251 192.168.200.251 1
2. Delete the route that has the same address as the loopback interface.
C:\>route delete 192.168.200.0 mask 255.255.255.0 192.168.200.106
3. Display the route table again to verify that the unwanted route is gone.
C:\>route print Active Routes:
Network Address Netmask Gateway Address Interface Metric 0.0.0.0 0.0.0.0 192.168.204.254 192.168.200.251 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.200.0 255.255.255.0 192.168.200.251 192.168.200.251 1 192.168.200.106 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.251 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.255 255.255.255.255 192.168.200.251 192.168.200.251 1 224.0.0.0 224.0.0.0 192.168.200.106 192.168.200.106 1 224.0.0.0 224.0.0.0 192.168.200.251 192.168.200.251 1 255.255.255.255 255.255.255.255 192.168.200.251 192.168.200.251 1 Long Method
The long method, like the short method, requires you to delete the route that NT creates when you add the loopback interface. However, what makes this method is long is that in some cases, when the route table has more than one route in the network that contains the loopback interface, the route delete command deletes the wrong route. In this case, you need to enter the command again to delete the route that has the loopback address, then re-add the other route.
1. Enter the route print command to display the server’s route table. In this example, the loopback interface has address 192.168.200.106. Notice that the route table also contains another route (192.168.200.250) in the same network. The 192.168.200.250 route is the gateway route and needs to stay in the route table.
C:\users\default>route print Active Routes:
Network Address Netmask Gateway Address Interface Metric 0.0.0.0 0.0.0.0 192.168.200.254 192.168.200.250 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.200.0 255.255.255.0 192.168.200.250 192.168.200.250 1 192.168.200.0 255.255.255.0 192.168.200.106 192.168.200.106 1 192.168.200.106 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.250 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.255 255.255.255.255 192.168.200.106 192.168.200.106 1 224.0.0.0 224.0.0.0 192.168.200.250 192.168.200.250 1 224.0.0.0 224.0.0.0 192.168.200.106 192.168.200.106 1 255.255.255.255 255.255.255.255 192.168.200.106 192.168.200.106 1
2. Enter the route delete command to delete the unwanted 192.168.200.106 route.
C:\users\default>route delete 192.168.200.0 mask 255.255.255.0 192.168.200.106
3. Display the route table again to verify the results. In this example, NT deletes the first 192.168.200.x route in the table instead of deleting the route you want to delete. If this occurs when you are performing this procedure, go to Step 4. Otherwise, you are through with this procedure.
C:\users\default>route print Active Routes:
Network Address Netmask Gateway Address Interface Metric 0.0.0.0 0.0.0.0 192.168.200.254 192.168.200.250 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.200.0 255.255.255.0 192.168.200.106 192.168.200.106 1 192.168.200.106 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.250 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.255 255.255.255.255 192.168.200.106 192.168.200.106 1 224.0.0.0 224.0.0.0 192.168.200.250 192.168.200.250 1 224.0.0.0 224.0.0.0 192.168.200.106 192.168.200.106 1 255.255.255.255 255.255.255.255 192.168.200.106 192.168.200.106 1
4. Enter the route delete command again to delete the unwanted route.
C:\users\default>route delete 192.168.200.0 mask 255.255.255.0 192.168.200.106
5. Display the route table again to verify the results. In this example, none of the 192.168.200.x routes remain in the table.
C:\users\default>route print Active Routes:
0.0.0.0 0.0.0.0 192.168.200.254 192.168.200.250 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.200.106 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.250 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.255 255.255.255.255 192.168.200.106 192.168.200.106 1 224.0.0.0 224.0.0.0 192.168.200.250 192.168.200.250 1 224.0.0.0 224.0.0.0 192.168.200.106 192.168.200.106 1 255.255.255.255 255.255.255.255 192.168.200.106 192.168.200.106 1
6. Enter the route add command to re-add the gateway route.
C:\users\default>route add 192.168.200.0 mask 255.255.255.0 192.168.200.250
7. Display the route table again to verify that the table contains the gateway route but does not contain a route with the loopback address.
C:\users\default>route print Active Routes:
Network Address Netmask Gateway Address Interface Metric 0.0.0.0 0.0.0.0 192.168.200.254 192.168.200.250 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.200.0 255.255.255.0 192.168.200.250 192.168.200.250 1 192.168.200.106 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.250 255.255.255.255 127.0.0.1 127.0.0.1 1 192.168.200.255 255.255.255.255 192.168.200.106 192.168.200.106 1 224.0.0.0 224.0.0.0 192.168.200.250 192.168.200.250 1 224.0.0.0 224.0.0.0 192.168.200.106 192.168.200.106 1 255.255.255.255 255.255.255.255 192.168.200.106 192.168.200.106 1