This one is really getting on my nerves. The cable segment length of fiber is what? In the book I am using it says 462 meters and then a few pages later it says 2km or more. I have looked and saw on a website that it depends wether it is running in half duplex or full duplex mode (not sure what the hell that has to do with anything) but can someone please clear this up....I am writing my cert soon and this is something I need a clear and definite answer for.
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Network+ question
- Thread starter FROGGYJ
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Accessdabbler
Technical User
I have the book "Upgrading and Repairing Networks" by Que. Inside the back cover is a list of cable lengths. Here's what it says:
10BaseFL - 2km segments, max. 4km segment length
100BaseFX - 412m segments, max. 2km segment length
1000BaseSX - 550m segments, max. 5km segment length
1000BaseLX - 5km segments, max. 5km segment length
1000BaseCX - 25m segments, max. 25m segment length (this is not fiber, it is a "twinaxial shielded cable"
The Max. Segment Length, I believe, is achieved by using repeaters since the book doesn't explain how the max. segment length is calculated.
Another book I have (All-in-One Network+ Certification by Mike Meyers) states that 100BaseFX has a segment of 400m (this is what you are saying is 462m I believe). This book also states that 1000BaseSX has a segment length of "over 500 metres (the exact length is really up to the various manufacturers)."
There seems to be no consensus on the segment length for 100BaseFX. Searching on the web was frustrating but I kept seeing 412m as the segment length (as well as 2km, 15km, sheesh!).
If this is the only thing you don't know, you're laughing!
10BaseFL - 2km segments, max. 4km segment length
100BaseFX - 412m segments, max. 2km segment length
1000BaseSX - 550m segments, max. 5km segment length
1000BaseLX - 5km segments, max. 5km segment length
1000BaseCX - 25m segments, max. 25m segment length (this is not fiber, it is a "twinaxial shielded cable"
The Max. Segment Length, I believe, is achieved by using repeaters since the book doesn't explain how the max. segment length is calculated.
Another book I have (All-in-One Network+ Certification by Mike Meyers) states that 100BaseFX has a segment of 400m (this is what you are saying is 462m I believe). This book also states that 1000BaseSX has a segment length of "over 500 metres (the exact length is really up to the various manufacturers)."
There seems to be no consensus on the segment length for 100BaseFX. Searching on the web was frustrating but I kept seeing 412m as the segment length (as well as 2km, 15km, sheesh!).
If this is the only thing you don't know, you're laughing!
- Thread starter
- #3
Actually I don't have the book right here but the 412 is sounding right. I think its just the stupid book in forgetting to mention repeaters. I have never used fiber optic in real life situations so 2km seems a little far fetched but hey it is light so who knows. The part that makes me scrath my head is just thinking that 10base5 has a longer segment length then fiber optic, but oh well I guess. I think I am going to stick with the 412m idea (for each segment) and a total segment length of 2km or more. Funny how all cable segments lengths are well explained everywhere in book and on the net except for this one. When i was reading about this half duplex/full deplux, I really starting wondering what the hell that had to do with cable segments, but this question has been irritating the hell out of me for a while and no IT guy I have talked to can give me a definite answer. I should convince my CEO to upgrade our network to fiber so I can play with this stuff then i will truly know the answer first hand and can finally close that question.
Accessdabbler
Technical User
I'm not an electrical engineer but I'm going to guess that the wavelength of light used for 100BaseFX has a maximum range of ~412m before it starts to dim.
Other wavelengths probably could be used to increase the distance but the specification for 100BaseFX settled on the substandard wavelength possibly due to the equipment required (cable specs, NICs, etc) to deliver the data cost-efficiently. Other fiber network standards, 1000BaseSX or LX for example, probably use a more refined wavelength and thus need more powerful fiber cables, NICs, etc., so it gets away with longer segments.
Again, this is my guess as to the reason for the shorter segments than 10Base5. Even if I'm dead wrong, it helps me rationalize the difference and makes it easier to memorize.
Other wavelengths probably could be used to increase the distance but the specification for 100BaseFX settled on the substandard wavelength possibly due to the equipment required (cable specs, NICs, etc) to deliver the data cost-efficiently. Other fiber network standards, 1000BaseSX or LX for example, probably use a more refined wavelength and thus need more powerful fiber cables, NICs, etc., so it gets away with longer segments.
Again, this is my guess as to the reason for the shorter segments than 10Base5. Even if I'm dead wrong, it helps me rationalize the difference and makes it easier to memorize.
- Thread starter
- #5
Well I know the answer now and the reason for all the confusion is wether you are using multimode or singlemode cable. ahhh what a relief....oh the multi is the 412m and the single is like 10,000 so there finally put an end to that. Thanks to the Exam Cram2 Network+ book, I just bought that over the weekend and it was a good read if anyone is interested in knowing.
No I am not affiliated in anyway with Exam Cram, just a review.
No I am not affiliated in anyway with Exam Cram, just a review.
Accessdabbler
Technical User
I wrote the Network+ Exam last week. Passed with 833/900. Most of the questions were easy. From my experience, be sure you know about WinNT and how it works on a network. I had a bunch of questions about moving a WinNT computer from one segment to another or configuring a network when WinNT is being used. Be sure you know how network names can be resolved using NetBEUI through routers.
- Thread starter
- #7
"Be sure you know how network names can be resolved using NetBEUI through routers"
That raised my eyebrow.....I understand name resolution and all but to my knowledge NetBeui is a non-routable protocol therefor this shouldn't work....although I have never really tested it. Can you give maybe the example of that question and they way it was worded....maybe I am not understanding the wording here.
That raised my eyebrow.....I understand name resolution and all but to my knowledge NetBeui is a non-routable protocol therefor this shouldn't work....although I have never really tested it. Can you give maybe the example of that question and they way it was worded....maybe I am not understanding the wording here.
Accessdabbler
Technical User
I don't remember specific questions but one involved moving a WinNT system from one segment to another. WinNT was using NetBEUI.
After moving the WinNT system, the WinNT box was unable to access its previous server. Why?
The answers boiled down to two options:
A. NetBEUI is not routable
B. The router is blocking port 139
(the question did not specifically state that there even was a router in the LAN)
I believe I answered A because even though Port 139 involves NetBIOS, I didn't think it was relevant. I have no way of knowing if I got this one correct.
I seem to remember another question about moving a WinNT system that could not get an IP address by DHCP (or something like that) after the move to another segment. There was no mention of whether there was a WINS server but the choices involved whether the WINS server was the problem, DNS or the DHCP IP address. Frankly, I forgot whether WinNT required WINS or not (I think it does).
Another, unrelated question I had involved a DSL modem problem. All the lights worked on the modem but the user could not access the internet. The system and modem were rebooted, all lights worked but still no access (access did work previously). I don't remember the choices but I THINK the answer was that the modem was malfunctioning. This one puzzled me since I never really thought about whether the modem lights could still come on yet the modem is broken in some way.
One question asked to show which devices had loopback capabilities. You had to pick 2 (or was it 3?) from a list of (going by memory) 1. CSU/DSU 2. Router 3. Switch 4. Bridge 5. Hub 6. Managed Hub. I think I got this one wrong (CSU/DSU has loopback but the others? I dunno. Probably 1, 2 and 3 but I may have answered 1, 2 and 6 - I forgot the difference between a hub and managed hub).
Last, a rather amusing question involved moving the demarc in the building. You are assisting the senior network dude, what tool should you bring? This was one of those, "bring the whole damn toolbox!" answers but, of course, you had to pick 1 tool. Choices were 1. Toner 2. Punchdown tool 3. BERT (Bit Error Rate Tester) 4. I Don't remember.
I picked BERT (figured you'd want to test the lines? Hmmm, I think BERT is used in fibre installations...). I know I got this one wrong. I remember thinking during the exam "Probably need a hammer, screwdriver, circular saw, wheelbarrow, med. kit, eye-wash solution, ..."
After moving the WinNT system, the WinNT box was unable to access its previous server. Why?
The answers boiled down to two options:
A. NetBEUI is not routable
B. The router is blocking port 139
(the question did not specifically state that there even was a router in the LAN)
I believe I answered A because even though Port 139 involves NetBIOS, I didn't think it was relevant. I have no way of knowing if I got this one correct.
I seem to remember another question about moving a WinNT system that could not get an IP address by DHCP (or something like that) after the move to another segment. There was no mention of whether there was a WINS server but the choices involved whether the WINS server was the problem, DNS or the DHCP IP address. Frankly, I forgot whether WinNT required WINS or not (I think it does).
Another, unrelated question I had involved a DSL modem problem. All the lights worked on the modem but the user could not access the internet. The system and modem were rebooted, all lights worked but still no access (access did work previously). I don't remember the choices but I THINK the answer was that the modem was malfunctioning. This one puzzled me since I never really thought about whether the modem lights could still come on yet the modem is broken in some way.
One question asked to show which devices had loopback capabilities. You had to pick 2 (or was it 3?) from a list of (going by memory) 1. CSU/DSU 2. Router 3. Switch 4. Bridge 5. Hub 6. Managed Hub. I think I got this one wrong (CSU/DSU has loopback but the others? I dunno. Probably 1, 2 and 3 but I may have answered 1, 2 and 6 - I forgot the difference between a hub and managed hub).
Last, a rather amusing question involved moving the demarc in the building. You are assisting the senior network dude, what tool should you bring? This was one of those, "bring the whole damn toolbox!" answers but, of course, you had to pick 1 tool. Choices were 1. Toner 2. Punchdown tool 3. BERT (Bit Error Rate Tester) 4. I Don't remember.
I picked BERT (figured you'd want to test the lines? Hmmm, I think BERT is used in fibre installations...). I know I got this one wrong. I remember thinking during the exam "Probably need a hammer, screwdriver, circular saw, wheelbarrow, med. kit, eye-wash solution, ..."
- Thread starter
- #9
Man those are some tricky questions....
1.you're right, NetBEUI is non-routable!
2.WinNT doesn't "have to have" WINS server on the network...you could always use the LMHOSTS file if you like.
3.would have to see the modem question
4.this is a weird question but I would guess the CSU/DSU, a router and a bridge
5.this one is another tricky one as I would bring the wheelbarrow, but hey other then that I would bring the punchdown tool. BERT is a good idea and all, but just thinking of the room and the cabling, its not all pretty RJ-45's everywhere....there are strand after strands of tiny wires all over the place!!! and without your punchdown tool....well have fun!
Anyone else have any input on these answers?
1.you're right, NetBEUI is non-routable!
2.WinNT doesn't "have to have" WINS server on the network...you could always use the LMHOSTS file if you like.
3.would have to see the modem question
4.this is a weird question but I would guess the CSU/DSU, a router and a bridge
5.this one is another tricky one as I would bring the wheelbarrow, but hey other then that I would bring the punchdown tool. BERT is a good idea and all, but just thinking of the room and the cabling, its not all pretty RJ-45's everywhere....there are strand after strands of tiny wires all over the place!!! and without your punchdown tool....well have fun!
Anyone else have any input on these answers?
Accessdabbler
Technical User
I figure I got 5 or 6 answers wrong out of 72 so I guess I should be happy. Never having worked in a large networked company I really had no idea what tool to use to move the demarc (I know what a demarc is, just never seen one!).
My only regret is not fully understanding NetBIOS name resolution before I wrote the exam. Yeah, I know what WINS does and the difference between HOSTS and LMHOSTS but it would have been clearer if I had actually sniffed the name resolution process in an active network. In fact, could a Win2K network resolve names under these circumstances?
1. NetBEUI is NOT installed on any system
2. There is no WINS server or DNS server.
3. No HOSTS or LMHOSTS file.
Assuming the answer is no, what if NetBEUI is installed but NetBEUI over TCP/IP is not allowed? What problems would there be?
How do you actually setup local name resolution on a DNS server in the network?
This is what I mean by not having a full concept of name resolution. I know what all the pieces do, just not how to apply it all in a real network. It would have been very helpful to have had access to a network with a server and try these different scenarios. If you can answer these questions, you'll probably ace the exam!
In a way, it's kinda embarrassing to do very well on the Network+ exam without ever having seen a server! Makes one wonder about the validity of Net+ Certification.... However, I do know that I learned a lot during my studies (more than the Network+ expects) and that once I can get a job in a network environment, it won't take me long to fly to the top!
My only regret is not fully understanding NetBIOS name resolution before I wrote the exam. Yeah, I know what WINS does and the difference between HOSTS and LMHOSTS but it would have been clearer if I had actually sniffed the name resolution process in an active network. In fact, could a Win2K network resolve names under these circumstances?
1. NetBEUI is NOT installed on any system
2. There is no WINS server or DNS server.
3. No HOSTS or LMHOSTS file.
Assuming the answer is no, what if NetBEUI is installed but NetBEUI over TCP/IP is not allowed? What problems would there be?
How do you actually setup local name resolution on a DNS server in the network?
This is what I mean by not having a full concept of name resolution. I know what all the pieces do, just not how to apply it all in a real network. It would have been very helpful to have had access to a network with a server and try these different scenarios. If you can answer these questions, you'll probably ace the exam!
In a way, it's kinda embarrassing to do very well on the Network+ exam without ever having seen a server! Makes one wonder about the validity of Net+ Certification.... However, I do know that I learned a lot during my studies (more than the Network+ expects) and that once I can get a job in a network environment, it won't take me long to fly to the top!
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