Valid encapsulation types

[k0mbachi]

I'm in the process of encoding questions from Wendell Odom's book, the Cisco Esim product and the Cisco Flash product into one editable data base so I can append references and comments at will. In the Cisco Flash product, the question below has only one answer: D, while one of the earlier tomes listed both C and D. Is HDLC a valid IPX encapsulation type?

27. Which of the following is not a valid IPX encapsulation type on a Cisco router?
A. SAP
B. ARPA
C. HDLC
D. PPP

Answer: C, D

 

[dogbert2]

HDLC is not a valid frame type for IPX, as I recall, there are 4 frame types for IPX (ethernet, ethernet II, SNAP, and ARPA).

Now, could IPX work over two cisco routers using HDLC encap?, it should.

 

[k0mbachi]

Well, thank you for clearing that up, dogbert2!

 

[ajman]

odom CD got many errors!

 

[k0mbachi]

Yes, I know. I've been communicating...sort of...with some folks from Cisco Press. One offered my money back, the other seemed to feel I wasn't using properly and provided some instructions, to no avail. Actually the same problem seems to exist on Odom's CD, the Cisco ESIM and the Cisco Flash Product. Thus, I may need my money back on all if the matter don't get resolved before I pass the CCNA. The macromedia driver is an example of what I learned in Astronomy 201: Complexity is a disarrangement of simplicity.

I replied back to CP with a step by step accounting of my keystrokes and I haven't heard from 'em. Just for grins, ajman, what O/S are you using?

 

[AlexNdr]

k0mbachi, you know there are 4 different IPX encapsulation types for Ethernet (arpa, novell-ether, sap and snap), 2 for Token Ring and 3 for FDDI. What all of them have in common is that they are used in LANs! Both HDLC and PPP are used in Cisco routers' serial WAN interfaces. As Cisco routers support IPX routing, IPX can be encapsulated in both layer 2 protocols HDLC and PPP. However, the phrase "IPX encapsulation" is normally (or always) used to refer to encapsulation in LAN environments (ARPA, novell-ether, ...).

Conclusion:
1. If it's a single-answer choice, select D. (PPP) (Maybe because PPP is not Cisco-proprietary and Cisco-HDLC is??? Hmmm...) It's a tricky question if they include both HDLC and PPP in the group of choices!
2. If it's a multiple-answer choice ("Select two&quot, then select C. and D. with no doubt!

I hope it helps, k0mbachi.

 

[k0mbachi]

AlexNDR: Yes, I have learned that 802.3 aka novell-ether is the default encapsulation, 802.2 and sap are the same, as is Ethernet_II and ARPA and SNAP=SNAP both in Cisco and Novell environments. Note the question asks "Which of the following is not a valid IPX encapsulation type on a Cisco router?" However, if I understand you correctly, the layer 2 IPX encapsulation types CAN be further encapsulated by layer 2 HDLC (perhaps for traversing a serial link)? "SAP and ARPA are both LAN protocols while HDLC and PPP are WAN protocols?", he asked. The word protocol is a pretty generic catch-all, I've discovered, applicable to encapsulation types, transports and other networking buzzwords. I thought the official Sniffer Technologies Guide to Communication Protocols which I've recently discovered would solve some of these problems, but actually that chart has introduced a bit more confusion.

 

[AlexNdr]

k0mbachi, you're right about the word "protocol" being "pretty generic catch-all". For example, Ethernet is called a "layer 1 and 2 protocol" and also called "LAN technology".

With respect to IPX encapsulation over WAN links, I understand that IPX packets are directly encapsulated and not "tunneled", since arpa, sap, etc. are only valid in LAN connections (Ethernet, Token Ring, FDDI). Routers send and receive IPX packets over their WAN interfaces the same way they do with IP packets: encapsulated in a WAN data link layer protocol, like PPP or HDLC. That's how I think it works.

Anyway, I'm glad I didn't get a question like the one you posted in my CCNA exam (if it were a select-one choice).