• Are there any software packages I must have before using the VPN?
• While attempting to install the Linux VPN client, I get a "make module" error. How do I fix this?
• I installed the Linux VPN client successfully, but I am still unable to connect. Could this be an issue with my firewall?

Are there any software packages I must have before using the VPN?

Yes. You must have the C compiler (e.g. gcc) on your system before you can install the VPN client.

While attempting to install the Linux VPN client, I get a "make module" error. How do I fix this?

If you get an error similar to:

Failed to make module "cisco_ipsec"

during the installation of the Cisco VPN client for Linux, there are a few steps you can take to resolve the problem, depending on your kernel:

• If you are running the default kernel from the manufacturer of your version of Linux, you should install the corresponding kernel-sources rpm. There should also be a symlink from /lib/modules/<version>/build to the source directory. The installation module will look for this link first, as the default value at the kernel source prompt.
• If you are running your own kernel, you must use the build tree from your kernel to build the client. Unpacking the source code for the version of your kernel is insufficient. The module build process must use the same configuration information as your running kernel, and the only way to get that information is from the directory tree that was used to build the running kernel.

I installed the Linux VPN client successfully, but I am still unable to connect. Could this be an issue with my firewall?

Yes.  If you have a firewall running on your Linux machine, you should make sure to configure it to allow the following so VPN traffic will pass through:

• UDP port 500 & 10000 (any port used for IPSec/UDP)
• TCP port 10000 configured for IPSec/TCP
• NAT-T port 4500
• IP protocol 50 (ESP)
• IP protocol 51 (AH)