Study question, please help!

[SnowNinja]

Okay, I'm not sure I agree with the answer in my study guide. Can someone put in their 2 cents?

A new frame-relay network is being implemented and inverse ARP does not appear to be operating correctly. Which alternative command can be used to provide connectivity?

A. frame-relay arp
B. frame-relay map
C. frame-relay interface-dlci
D. frame-relay lmi-type
E. frame-relay pvc


-SnowNinja

 

[Cluebird]

Inverse ARP is used to dynamically map ip addresses (destination) to DLCIs (local). If Inverse ARP isn't working, static maps can fix the problem so B is the answer IMHO. There could be an LMI problem as well, but the frame map will be the fastest way to get connectivity which is what the question seems to be asking.

 

[SnowNinja]

So, really, there's no way for C to be the answer then? I figured B as well, but the study guide says C.

-SnowNinja

 

[jabw]

I've checked it with My CCNA ICND Cisco book and also with the CCNA Study guide from McGrawHill.
Both make me believe that Inverse ARP creates a mapping between Layer 3 (IP) addresses and the Layer 2 (DLCI) address.
If Inverse ARP is not activated than this mapping needs to be done manually using frame relay map.
So I would vote for anser B.

btw what book/study guide are you using?

 

[SnowNinja]

Yes, I agree. B sounds more logically consistent. I wouldn't mind hearing an oposing view, though.

-SnowNinja

 

[Jsteve]

both B and C are correct depending on which topology that is used.

You use the "Interface-dlci" when you use subinterfaces with point-to-point communication.

And you use "map" when you use subinterfaces with multipoint communication.

int s0.1 [multipoint | point-to-point]

I assume that you have a pic that goes with the question, which should tell you what the answer is.

http://www.cisco.com/univercd/cc/td/doc/product/software/ssr921/cscg/79490.htm

 

[Cluebird]

Frame-relay gets more complex when you have subinterfaces since things no longer happen automatically. Point-to-point subinterfaces require DLCIs be specified. Point-to-multipoint need static maps. Running routing protocols adds even more pitfalls. You have to read the question closely, review the topology, and know the difference between implementations.

If LMI isn't working, InverseArp won't work, either. Just be careful with study guides, because many of them have errors or incomplete information.

 

[andreyts]

B

Best Regards,

Andrey
CCNA

 

[techkiwi]

I would agree with Jsteve.

My Cisco ICND course manual says that a frame-relay connection requires the local DLCI be mapped to a destination network layer address. This can be dynamically mapped with Inverse ARP, or you can manually configure a static frame-relay map. So your answer in this case would be B.

A few pages later it heads into subinterfaces, and states "If you configured the subinterface as point-to-point you must configure the local DLCI for the subinterface to distinguish it from the physical interface. It is also required for multipoint subinterfaces for which Inverse ARP is enabled. It is not required for multipoint subinterfaces configured with static route maps." The answer in this case is C.

Based just on the wording of the question, I would guess B. If there was a diagram showing subinterfaces though, I'd go for C.