This was not covered much at all in my study materials, I am guessing because they were made as the new exam version rolled over, and they hadn’t introduced a lot of PPPoE just yet (is my only thought on why this was not covered to the extent it should have been).
PPPoE has 2 phases you need to know about:
- Active Discovery – Where the client actively discovers PPPoE Servers
- PPP Session Phase – Where client does negotiation and authentication
Do NOT forget those two phases, and that simple explanation of what they do, chant them until they are your mantra or scream them out loud until you can’t get the voices out of your head!
One thing also to note, beyond the session phase doing negotiation and authentication, there is one very important Layer specific data transmission now allowed to occur:
PPPoE now acts as a Layer 2 encapsulation method for data transmission over PPP Links with PPPoE Headers.
I would burn that into your brain, because its so easy to think it’s Layer 3, but when your in the exam room and if you get the topic, PPPoE question = Layer 2 encapsulation.
PPPoE uses the command “Dialer Persistent” to keep idle lines from going down due to lack of interesting traffic.
To authenticate with an Encrypted password, use CHAP, for clear text you’d use PAP.
If you are using a VPDN Group for PPPoE, you must first issue the command “vpdn enable” command before you can configure VPDN Goups. To enable VPDN Groups:
- conf t
- vpdn enable
- vpdn-group (name)
- protocol pppoe
This should have you covered for PPPoE on exam day, but I would heed my word, when I say you need to remember all of it down the word and syntax I highly advise you heed my warning 🙂