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TRICK QUESTION HERE... Help Needed
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| SuperCertMan 2002-01-14, 5:25 pm |
| The Question goes:
Which of the following is true of full mesh frame relay design, as it is compared to partial mesh design?
a. split horizon limits connectivity in a full mesh.
b. full mesh is more expensive becaue it requires more routers.
c. Partial mesh requires more admiistrative overhead.
d. partial mesh is less expensive because fewer virtual circuits are required.
I think it's B. but then again i think it might not because in a partial mesh, there can be the same amount of routers, just not as many connections... any opinions? | |
| Yeti-GBR1 2002-01-14, 7:45 pm |
| My gut feeling (having not even looked at this stuff yet) would be D the reason being that full mesh requires all routers to be inter-connected where as partial mesh does not, thus will be less expensive(patrial mesh will be) than full mesh..Make any sense?
B cannot be correct since it does not need more routers...unless your routers do not have the required interfaces 
C is wrong because Full Mesh will have more admin overhead than partial mesh, this is common sense since there will be less virtual routes to administer in partial mesh.
Not sure about A though...kinda on sticky ground on this one biut if I had to choose 2 then it would be A & D if I have to choose one then it would be D.
Hope this helps in some small way. | |
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| D only. With frame relay you pay per VC so obviously the more VC's the more expensive.
I agree with Yeti on B and C, with respect to A have a look at http://www.cisco.com/warp/public/125/26.html which is frame relay characteristics which states that split horizon is disabled.
It may be worth you having a look at your CCNA notes as this is where frame relay is covered.
It's good to see a question, we haven'tr had one for a while.
What does everybody else think?? | |
| FastIP 2002-01-15, 8:01 am |
| I agree with the above.
Answer - D
Partial mesh has the same number of routers as full mesh. The only difference is that you have to have FULL connectivity between all the routers in a full mesh ( expensive).
With a partial mesh you can have connectivitiy to other routers without having to pay for the more expensive option of full mesh. Hence it is cheaper. | |
| FastIP 2002-01-15, 8:02 am |
| Answers A & C are obviously incorrect | |
| Yeti-GBR1 2002-01-15, 8:50 am |
| Ok forgive my stupidity (and no I have not read the article posted by Mat.P yet) why is A wrong then? | |
| faldrous 2002-01-15, 10:36 am |
| without any doubt,D IS THE ANSWER.CHECK THE CCDA STUDY GUIDE BY CISCO. | |
| SuperCertMan 2002-01-15, 11:41 am |
| well thanks for clarifying that fellas, now i hope i see that question on the exam... i'm gonna be as patient as possible with those damn case studies... i'll let you know what happens... wish me luck... | |
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| quote:
Originally posted by Yeti-GBR1
Ok forgive my stupidity (and no I have not read the article posted by Mat.P yet) why is A wrong then?
The link starts:-
IP split horizon checking is disabled by default for Frame Relay encapsulation so routing updates will come in and out the same interface.
So from this I would say that Spanning tree doesn't limit connection in a full mesh network because it's disabled.
However (big however), This seems to contradict what is said in my CCNA notes where it disusses split horizon.
Anybody have any thoughts?? | |
| SuperCertMan 2002-01-15, 4:19 pm |
| I got a decent 873 out of 1000 not too bad... and i got that question on the exam and i chose D, which must have been correct because i got 100% on WAN Technologies and Design the Network Structure of the test. Thanks for all your help... 70-210 is next!!! | |
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| Well done.
OK so it may have been the correct answer, but it doesn't answer the question fully.
Why is A wrong?? My 2 references, the Cisco web site and the CCNA notes appear to contradict each other. | |
| huntert 2002-01-15, 5:57 pm |
| d. partial mesh is less expensive because fewer virtual circuits are required.
Well since its frame and virtual circuits are a factor Answer d makes lots of sense.
Partial mesh = less virtual circuits and endpoints compared to full mesh.
That question was easy hope my exam is nice enough to give me Qs like that. | |
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| I agree D and have done all along.
However I aren't 100% convinced about A and NEED convincing. If the question had specified 1 answer then D would have been it - I then would have gone for A if it required 2 answers - but wouldn't have been positive.
HunterT if it's so easy, explain why A is wrong. Both the references I referred to contradict each other. | |
| FastIP 2002-01-16, 6:23 am |
| Well MatP,
Referring to Answer A and split horizon in FR Full Mesh limiting connectivity..
http://www.cisco.com/warp/public/125/26.html
IP Split Horizon Checking
IP split horizon checking is disabled by default for Frame Relay encapsulation so routing updates will come in and out the same interface. The routers learn the data-link connection identifiers (DLCIs) they need to use from the Frame Relay switch via Local Management Interface (LMI) updates. The routers then use Inverse ARP for the remote IP address and create a mapping of local DLCIs and their associated remote IP addresses.
Additionally, certain protocols such as AppleTalk, transparent bridging, and IPX cannot be supported on partially meshed networks because they require "split horizon," in which a packet received on an interface cannot be transmitted out the same interface, even if the packet is received and transmitted on different virtual circuits. Configuring Frame Relay subinterfaces ensures that a single physical interface is treated as multiple virtual interfaces. This capability allows us to overcome split horizon rules. Packets received on one virtual interface can now be forwarded out another virtual interface, even if they are configured on the same physical interface.
i hope this helps | |
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| thanks but youve just copied my first post!! I then looked at the CCNA notes when I had a chance and these contadicted it!!
Thanks for looking anyway - I guess I'll just have to try and get hold of a lab/customer with this setup. |
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