TCP Versus UDP

In this video, we examine the Transport Layer of the OSI model.


Troubleshooting Basic IPSec VPNs on the Cisco ASA

As I prepare for my next (and final) attempt at the CCIE Security lab exam, I am making lists to help speed and accuracy when troubleshooting involved configurations like VPNs. Here is an example list for a basic VPN on the Cisco ASA:


Step 1 – Is ISAKMP enabled on the correct interface? crypto isakmp enable OUTSIDE

Step 2 – Check the ISAKMP policy.

Step 3 – Check the tunnel-group for correct pre-shared key.

Step 4 – Check the transform set.

Step 5 – Check the access-list for interesting traffic definition.

Step 6 – Check the crypto map.

Step 7 – Check the application of the crypto map.

In the heat of battle you can find that having a plan sure beats not having a plan at all. 🙂

The Internet Layer

In this video, learn the details behind the technologies found in the Internet layer of the famous OSI model.