Recovering from Hosts File Errors When Using Application Access
The following errors can occur if you do not close the Application Access window properly:
- The next time you try to start Application Access, it may be switched off; you receive a
Backup HOSTS File Found error message.
- The applications themselves may be switched off or malfunction, even when you are running them locally.
These errors can result from terminating the Application Access window in any improper way. For example:
- Your browser crashes while you are using Application Access.
- A power outage or system shutdown occurs while you are using Application Access.
- You minimize the Application Access window while you are working, then shut down your computer with the window active (but minimized).
This section includes the following topics:
Understanding the hosts File
The hosts file on your local system maps IP addresses to hostnames. When you start Application Access, Clientless SSL VPN modifies the hosts file, adding Clientless SSL VPN-specific entries. Stopping Application Access by properly closing the Application Access window returns the file to its original state.
Before invoking Application Access...
hosts file is in original state.
When Application Access starts....
- Clientless SSL VPN copies the hosts file to hosts.webvpn, thus creating a backup.
- Clientless SSL VPN then edits the hosts file, inserting Clientless SSL VPN-specific information.
When Application Access stops...
- Clientless SSL VPN copies the backup file to the
hosts file, thus restoring the hosts file to its original state.
- Clientless SSL VPN deletes hosts.webvpn.
After finishing Application Access...
hosts file is in original state.
NoteMicrosoft anti-spyware software blocks changes that the port forwarding Java applet makes to the hosts file. Seewww.microsoft.com for information on how to allow hosts file changes when using anti-spyware software.
Stopping Application Access Improperly
When Application Access terminates abnormally, the
hosts file remains in a Clientless SSL VPN-customized state. Clientless SSL VPN checks the state the next time you start Application Access by searching for a hosts.webvpn file. If it finds one, a
Backup HOSTS File Found error message appears, and Application Access is temporarily switched off.
Once you shut down Application Access improperly, you leave your remote access client/server applications in limbo. If you try to start these applications without using Clientless SSL VPN, they may malfunction. You may find that hosts that you normally connect to are unavailable. This situation could commonly occur if you run applications remotely from home, fail to quit the Application Access window before shutting down the computer, then try to run the applications later from the office.
Reconfiguring a Host’s File Automatically Using Clientless SSL VPN
If you are able to connect to your remote access server, follow these steps to reconfigure the host’s file and re-enable both Application Access and the applications.
Step 1 Start Clientless SSL VPN and log in. The home page opens.
Step 2 Click the Applications Access link. A
Backup HOSTS File Found message appears.
Step 3 Choose one of the following options:
- Restore from backup —Clientless SSL VPN forces a proper shutdown. It copies the hosts.webvpn backup file to the
hosts file, restoring it to its original state, then deletes hosts.webvpn. You then have to restart Application Access.
- Do nothing —Application Access does not start. The remote access home page reappears.
- Delete backup —Clientless SSL VPN deletes the hosts.webvpn file, leaving the hosts file in its Clientless SSL VPN-customized state. The original
hosts file settings are lost. Application Access then starts, using the Clientless SSL VPN-customized hosts file as the new original. Choose this option only if you are unconcerned about losing hosts file settings. If you or a program you use may have edited the hosts file after Application Access has shut down improperly, choose one of the other options, or edit the hosts file manually. (See “Reconfiguring hosts File Manually.”)
Reconfiguring hosts File Manually
If you are not able to connect to your remote access server from your current location, or if you have customized the hosts file and do not want to lose your edits, follow these steps to reconfigure the hosts file and reenable both Application Access and the applications.
Step 1 Locate and edit your hosts file. The most common location is c:\windows\sysem32\drivers\etc\hosts.
Step 2 Check to see if any lines contain the string:
server1 # added by WebVpnPortForward
server1.example.com invalid.cisco.com # added by WebVpnPortForward
server2 # added by WebVpnPortForward
server2.example.com invalid.cisco.com # added by WebVpnPortForward
server3 # added by WebVpnPortForward
server3.example.com invalid.cisco.com # added by WebVpnPortForward
# Copyright (c) 1993-1999 Microsoft Corp.
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
# This file contains the mappings of IP addresses to hostnames. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding hostname.
# The IP address and the hostname should be separated by at least one
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
# 220.127.116.11 cisco.example.com # source server
# 18.104.22.168 x.example.com # x client host
# added by WebVpnPortForward If any lines contain this string, your hosts file is Clientless SSL VPN-customized. If your hosts file is Clientless SSL VPN-customized, it looks similar to the following example:
Step 3 Delete the lines that contain the string:
# added by WebVpnPortForward
Step 4 Save and close the file.
Step 5 Start Clientless SSL VPN and log in.
The home page appears.
Step 6 Click the Application Access link.
The Application Access window appears. Application Access is now enabled.