|Virtual Router ID||Austonomous System (AS)|
Believe me or not, aside from passing an exam there is another important reason why you should know what is inside the EIGRP packet header. Any hypothesis?
The Job Interview
You thought you know everything when you got the Cisco professional level certification but what happens when the interviewer asked you about what is inside the EIGRP packet header? You memorized all the configurations commands. You know what is BGP route reflector. You know how to do unequal load balancing in EIGRP. You even know how to configure fabric path, ASA firewalls, and do site-to-site VPN. You know everything you did in your laboratory but you forgot what is inside the EIGRP packet header.
You often heard about AS (Autonomous System) since the beginning of your BGP study. By now, you know that when we talk about AS we are referring to set or group of routers operating with same routing policy under a single administrative domain/control. The AS number should be unique to identify them in the internet. It is 16-bit in size allowing 65536 AS to be used in BGP. However, not all are available for use. Some are reserved for documentation purposes and the rest are divided for private and public use.
When I first heard about Interior Gateway Protocol (IGP) and Exterior Gateway Protocol (EGP), I was just like, “what on bits and bytes are these?” If you are new to networks and you suddenly heard these on your first day, you might ignore the meaning and also the importance. However, you don’t have to memorize the meaning because you will know it by heart as days go by. (more…)