Frame-relay question for ICND1

JSK

I've been scratching my head on this question from my Transcender ICND1 practice exam. Basically, you're an administrator troubleshooting a frame-relay problem. When you try to pin the remote router across the frame-relay connection, the ping fails. The question states that you have identified the issue as a possible encapsulation mismatch. What should you do to resolve the problem?

A. Change the encapsulation type to IETF on both routers.
B. Use the show frame-relay pvc command to verify the PVC status.
C. Use the show frame-relay pvc command to view the encapsulation type.
D. Change the encapsulation type to Cisco on both of the routers.


I have to admit that I really did not know the answer to the question. So I guessed C. But it turns out the correct answer is A. They reference this link which discusses the answer. Troubleshooting Frame Relay Connections - Cisco Systems

I know that discussing the exam is not allowed. But honestly, can I really expect this kind of question on the ICND1 exam? I'm starting to suspect the Transcender practice exam is going to be tougher than the actual exam. In additon to this question, I have had at least 2 other questions which ask hardware specific questions such as how many serial ports does a Cisco 25xx router have.

chmorin

Well looking at those answer choices an educated guess could have gotten it right.

B is a show command, it does not change anything so it wont resolve the problem
C is the same.
D says an encaplation type is cisco, which does not exist as an encapsulation type.

I hate frame relay, but some WAN technology is going to be in the exam. That is what lowered my grade temendiously. It is worth understanding. Maybe looking up IETF and frame relay would help: Cisco Frame Relay Configurations > Enabling Frame Relay Encapsulation

Best of luck on the exam.

alan2308

^^^^ What he said. You'd be surprised how many times you're able to stumble into the correct answer by being able to eliminate the other three choices. Thats why when you're studying, its just as important to understand why the other three choices aren't the correct answer as it is to understand why the correct answer is correct.

JSK

Thanks guys. I appreciate the responses.

I think I was just caught off guard with the question. I honestly do not remember even covering IETF in any of my studies so far. My elementK courseware and Odom's ICND1 book do not really mention it. But I did find some info in Lammle's CCNA book that should help.

Back to studying.

jmc012

JSK wrote: »

I've been scratching my head on this question from my Transcender ICND1 practice exam. Basically, you're an administrator troubleshooting a frame-relay problem. When you try to pin the remote router across the frame-relay connection, the ping fails. The question states that you have identified the issue as a possible encapsulation mismatch. What should you do to resolve the problem?

A. Change the encapsulation type to IETF on both routers.
B. Use the show frame-relay pvc command to verify the PVC status.
C. Use the show frame-relay pvc command to view the encapsulation type.
D. Change the encapsulation type to Cisco on both of the routers.


I have to admit that I really did not know the answer to the question. So I guessed C. But it turns out the correct answer is A. They reference this link which discusses the answer. Troubleshooting Frame Relay Connections - Cisco Systems

I know that discussing the exam is not allowed. But honestly, can I really expect this kind of question on the ICND1 exam? I'm starting to suspect the Transcender practice exam is going to be tougher than the actual exam. In additon to this question, I have had at least 2 other questions which ask hardware specific questions such as how many serial ports does a Cisco 25xx router have.

Did it say anything about the other router being a non-Cisco router? I find that question a little confusing also, since the default is Cisco encapsulation. You just don't have to type Cisco when entering the encap frame-relay command. Seems to me you could just as easily put both routers to the default encap type if they are both Cisco.

Sepiraph

chmorin wrote: »

D says an encaplation type is cisco, which does not exist as an encapsulation type.

I hate frame relay, but some WAN technology is going to be in the exam. That is what lowered my grade temendiously. It is worth understanding. Maybe looking up IETF and frame relay would help: Cisco Frame Relay Configurations > Enabling Frame Relay Encapsulation

Best of luck on the exam.

Actually it does exist, it is either Cisco or IETF, and by default on Cisco it is actually the former.

JSK

jmc012 wrote: »

Did it say anything about the other router being a non-Cisco router? I find that question a little confusing also, since the default is Cisco encapsulation. You just don't have to type Cisco when entering the encap frame-relay command. Seems to me you could just as easily put both routers to the default encap type if they are both Cisco.

No, it does not mention whether the router is Cisco or another brand. Now that I've done some reading on IETF I can understand why that would be an important part of the question.

chmorin

Sepiraph wrote: »

Actually it does exist, it is either Cisco or IETF, and by default on Cisco it is actually the former.

Cisco is an LMI type, not encapsulation.

For encapsulations in frame relay your choices are (I think, at least at the CCNA level) frame-relay and IETF. Cisco highly prefers frame-relay.

Comprehensive Guide to Configuring and Troubleshooting Frame Relay [Frame Relay] - Cisco Systems

billyr

Frame Relay Encapsulation Types:

Cisco (Default)
IETF

LMI Types:
Cisco
Ansi
Q.933a.

Quoted from Cisco Press.
"Cisco supports two different Frame Relay encapsulation types. The default Frame Relay encapsulation enabled on supported interfaces is the Cisco encapsulation. Cisco also supports the IETF Frame Relay encapsulation type, which is in conformance with RFC 1490 and RFC 2427. RFC 2427 supercedes RFC 1490. Both RFC specifications define standards allowing multiple routed protocols to be carried over "

chmorin

billyr wrote: »

Frame Relay Encapsulation Types:

Cisco (Default)
IETF

LMI Types:
Cisco
Ansi
Q.933a.

Quoted from Cisco Press.
"Cisco supports two different Frame Relay encapsulation types. The default Frame Relay encapsulation enabled on supported interfaces is the Cisco encapsulation. Cisco also supports the IETF Frame Relay encapsulation type, which is in conformance with RFC 1490 and RFC 2427. RFC 2427 supercedes RFC 1490. Both RFC specifications define standards allowing multiple routed protocols to be carried over "

I'm going to go lab a frame relay situation and put encapsulation cisco and see what happens. To be honest, it looks like you totally misunderstood that quote.

EDIT:

I think I am wrong. I'll lab to confirm for everyone anyway.

chmorin

It is a little confusing, as it appears issuing the command "encapsulation frame-relay" will enable cisco encapsulation, but it does not directly say that.

I guess in all my practice labs back in the day I just assumed it was called frame-relay encapsulation. You know, because that is what you tell it to do. Leave it to cisco to make that more confusing than it should be.

Router(config)#int s0/0
Router(config-if)#enc?
encapsulation

Router(config-if)#encapsulation ?
  frame-relay  Frame Relay networks
  hdlc         Serial HDLC synchronous
  lapb         LAPB (X.25 Level 2)
  ppp          Point-to-Point protocol
  smds         Switched Megabit Data Service (SMDS)
  x25          X.25

Router(config-if)#encapsulation frame-relay ?
  MFR   Multilink Frame Relay bundle interface
  ietf  Use RFC1490/RFC2427 encapsulation
  <cr>

alan2308

billyr wrote: »

Frame Relay Encapsulation Types:

Cisco (Default)
IETF

LMI Types:
Cisco
Ansi
Q.933a.

Quoted from Cisco Press.
"Cisco supports two different Frame Relay encapsulation types. The default Frame Relay encapsulation enabled on supported interfaces is the Cisco encapsulation. Cisco also supports the IETF Frame Relay encapsulation type, which is in conformance with RFC 1490 and RFC 2427. RFC 2427 supercedes RFC 1490. Both RFC specifications define standards allowing multiple routed protocols to be carried over "

But the question didn't ask about the frame-relay type, it asked about the encapsulation type. The encapsulation types are (at least for this level) frame-relay, hdlc and ppp.

r2524(config-if)#encapsulation ?
  atm-dxi         ATM-DXI encapsulation
  bstun           Block Serial tunneling (BSTUN)
  frame-relay     Frame Relay networks
  hdlc            Serial HDLC synchronous
  ppp             Point-to-Point protocol
  sdlc            SDLC
  sdlc-primary    SDLC (primary)
  sdlc-secondary  SDLC (secondary)
  stun            Serial tunneling (STUN)

r2524(config-if)#encapsulation frame-relay ?
  ietf  Use RFC1490/RFC2427 encapsulation
  <cr>

Either option D. is missing a very key word or two, or you're reading too much into it. But based on what was asked, chmorin was correct.

thenjduke

I am going the route it is a encapsulation mistmatch between frame-relay, ppp, or hdlc because ICDN1 does not touch much on this subject.

alan2308

Ok, after reading the OP again, I'm going to have to go with B. A and D are frame-relay types, not encapsulation types as the question asked for, C is out because that command doesn't show the encapsulation type which was why it was asking you to issue it.

B works because it will show you if the PVC is down which will lead to frame-relay not being able to work across said PVC. This doesn't technically resolve the problem, but it does show you exactly what the problem is.

Edit: I guess what I'm getting at is that B is the least incorrect of the four.

billyr

alan2308 wrote: »

But the question didn't ask about the frame-relay type, it asked about the encapsulation type. The encapsulation types are (at least for this level) frame-relay, hdlc and ppp.

Alan my previous reply was aimed towards chmorin.

I think there is some confusion as to what I was getting at previously.
Frame Relay is your encapsulation type. However there are two forms of Frame Relay encapsulation type to choose from - Cisco's version which is turned on by default and known as Cisco applied when you enter the #Encaps Frame-Relay command, or IETF which is turned on when you enter the #Encaps Frame-Relay IETF command instead.

As to the question it is pretty vague in that it does not mention whether any of the routers are made by another vendor, which would normally require IETF. So i'd have to agree that the answer would be A.

My reason being that B & C are just show commands and would not resolve the situation.
D would work if both Routers were Cisco routers, but we don't know that from the description, A is therefore the more likely answer as even if they were or were not Cisco routers IETF is supported on both.

alan2308

I was just pointing out that there is a difference between "encapsulation type" and "frame-relay encapsulation type," and that the question only said "encapsulation type." I don't see how the two frame-relay encapsulation types are relevant to the question based on that.

But either way, I would have to assume that such a poorly worded question would not appear on a Cisco test. I took countless chapter quizzes, 4 practice finals, 4 actual finals and a couple practice full CCNA exams in the Academy and I never came across a question where I ended up picking which option what the least incorrect. Have I mentioned yet that I just really don't like this question?

billyr

alan2308 wrote: »

I was just pointing out that there is a difference between "encapsulation type" and "frame-relay encapsulation type," and that the question only said "encapsulation type." I don't see how the two frame-relay encapsulation types are relevant to the question based on that.

I have to disagree, the question stated that "the problem has been identified as an encapsulation mismatch" as none of the answers state that another protocol is in use by mistake such as HDLC or PPP etc then the only mismatch that could be going on is the mismatch between the two seperate types of Frame-Relay which are directly relevant to the question.

I may be wrong but I think whats going on here is that you are assuming that you have Frame-Relay as the encapsulation type - which is correct and thats it, that's what everthing gets encapsulated with, however there are two different forms of Frame-Relay to choose from which are not compatible with each other - Cisco and IETF.

Just like for example your leased lines or point to point links. You have a point to point protocol for your encapsulation, but different versions - HDLC the Cisco Default or PPP the industry standard, both not compatible.

But you are right, it is a poorly worded question.

chmorin

billyr wrote: »

But you are right, it is a poorly worded question.

Word.


...

alan2308

This is what I love about this forum. Nobody says "The answer is ___" and just leaves it at that.



And I did miss "the problem has been identified as an encapsulation mismatch" both times I read through the question. I don't hate this question any less, but I guess A and D both sound a bit better.

JSK

Not sure if this violates any forum rules but here is a screenshot of the question which includes an explanation of the answer.

alan2308

Two problems with the explination:

"However if the frame relay encapsulation is configured as Cisco, the Cisco devices will not be able to communicate with non-Cisco devices." How are we supposed to know if there are non-Cisco devices here? I never assume anything that wasn't specifically stated. Its just a bad idea.

"If the other device supported Cisco encapsulation, the link would be working." What if it does support Cisco encapsulation but it isn't configured to use Cisco encapsulation? Since we're making all kinds of assumptions already, why can't I assume that too? They could both be Cisco routers but one configured to use IETF. Maybe I'll just assume neither is Cisco, so IETF is the only option and therefore both routers are already configured as such.

This explination is no better than the question.

billyr

alan2308 wrote: »

This is what I love about this forum. Nobody says "The answer is ___" and just leaves it at that.



.

Hey don't knock it, this is the only place I'm allowed an opinion. At home there's only one that matters apparently and it aint mine.

chmorin

billyr wrote: »

Hey don't knock it, this is the only place I'm allowed an opinion. At home there's only one that matters apparently and it aint mine.

Naw noone is knocking at all, at least people here strive for the truth.

wbosher

I don't recall FR being part of the ICND1 exam.

chmorin

I wish:

Implement and verify WAN links
Describe different methods for connecting to a WAN
Configure and verify a basic WAN serial connection

Everyone's test is unique. Hehe. You could get lucky and see nothing of WAN.

rogue2shadow

wbosher wrote: »

I don't recall FR being part of the ICND1 exam.

I was about to say the same thing lol. Maybe this is for the composite.

alan2308

billyr wrote: »

Hey don't knock it, this is the only place I'm allowed an opinion. At home there's only one that matters apparently and it aint mine.

I didn't mean it sarcastically at all. I actually enjoy this types of open discussion/debate in contrast to, say, the "I LOVE APPLE!!" crowd that just keeps regurgitating whatever their lord Steve Jobs tells them.

Selfmade

I would assume that it's IETF, even though it doesn't say that there is one Cisco router and one non-Cisco router, that only makes sense because of how the question is worded.

but, IETF is not an encapsulation type, it's a LMI-type

that really is a poorly worded question, they could have just added

There is one Cisco router, and there is one non-Cisco router, encapsulation is configured, but when the network engineer tries to ping one router to the other, the ping fails. The engineer suspects that an incorrect LMI type is configured, which one is the correct type?

networker050184

Selfmade wrote: »

I would assume that it's IETF, even though it doesn't say that there is one Cisco router and one non-Cisco router, that only makes sense because of how the question is worded.

but, IETF is not an encapsulation type, it's a LMI-type

IETF is an encapsulation type. I think you have your LMI and encapsulation types mixed up. You should never get an LMI mismatch unless you hard code it because it is auto sensing on any recent IOS version.

Encapsulation: Cisco, IETF

LMI: Cisco, ANSI Annex D, Q933-A Annex A

alan2308

networker050184 wrote: »

IETF is an encapsulation type. I think you have your LMI and encapsulation types mixed up. You should never get an LMI mismatch unless you hard code it because it is auto sensing on any recent IOS version.

Encapsulation: Cisco, IETF

LMI: Cisco, ANSI Annex D, Q933-A Annex A

We've already spent way too long on this. Lets not go back there again.

networker050184

alan2308 wrote: »

We've already spent way too long on this. Lets not go back there again.

You guys have been going in circles on this all day. Just thought I'd let Selfmade and myself get in on the action too!