| Author |
Network layer question
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| nhat777 2002-06-17, 1:03 pm |
| Hi all,
which 4 functions are performed by the Network Layer of the OSI model?
A. It used a two part address
b. it maintains routing tables
c. it uses broadcast address
d. it establishes network addresses
e. it provides access to the LAN media
f. it provides media independence for upper layers
g. it provides path selection for Internet work communication
any help would be appreciated..
thanks,
N | |
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| hi nhat777,
which 4 functions are performed by the Network Layer of the OSI model?
A. It used a two part address
b. it maintains routing tables
c. it uses broadcast address
g. it provides path selection for Internet work communication
i guess..
have a good day..
Tamer Bayomy | |
| jeff_j_black 2002-06-17, 2:51 pm |
| I prefer 'D' over 'C' although I agree with the rest of your choices. To me a broadcast would only effect a single physical network, implying layer 2. Whereas 'D' is a continuation of the theme of 'A' & 'B'. What do you think? Love to discuss it! | |
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| i guess C is the correct answer beside A,B, and G... this is because if the address of the destination device is unknown to the router it will broadcast the packet to the remaining interfaces..
beside D is not correct since the network layer doesn't establish addresses but it use addresses to route packets...
that's what i think..
any other opinions..
Tamer Bayomy | |
| bcasey56k 2002-06-17, 8:24 pm |
| A, B, D & G would be my selections. | |
| nhat777 2002-06-17, 8:32 pm |
| Switches use broadcast address but not sure routers do. If routers do not then C is incorrect.
Router establishes network addresses? I'm not quite sure what does that mean.
c. it uses broadcast address
d. it establishes network addresses | |
| jeff_j_black 2002-06-17, 8:48 pm |
| Exactly my point:
First the question is about the network layer, not hardware. Second, broadcast is physical, routers are logical, networks are logical, I can't think of any layer that better defines network addresses than the network layer!?
Thats my reasons for eliminating 'c' but including 'd' for 'a, b, d, g' as the complete response. | |
| bcasey56k 2002-06-17, 9:14 pm |
| >Establishes network addresses.
I believe this refers to the source destination address being removed from a packet and being replaced with the destination address by the router. When I first saw this question I was also puzzled until I read the explanation somewhere regarding internal router processes. Please someone correct me if I'm wrong. | |
| jeff_j_black 2002-06-17, 9:24 pm |
| ... And routers work on the network level. | |
| chunder 2002-06-17, 11:59 pm |
| what kind of address is 192.168.0.255 given a 24 bit mask (255.255.255.0)? | |
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| let me correct myself, Routers discard packets for many reasons, one of them if there are no correct routes are known for sure the packet will be discarded. for that we do the default route.
but still routers doesn't establish network addresses..
what kind of address is 192.168.0.255 given a 24 bit mask (255.255.255.0)?
-it's directed broadcast..
Tamer Bayomy | |
| Imran4sin 2002-06-18, 5:16 am |
| Sup,
here is my 2 cents worth,
which 4 functions are performed by the Network Layer of the OSI model?
A. It used a two part address
vendor specific/manufacturer specific
b. it maintains routing tables
Helll no.. routing tables contains IP addresses and thats Network layer responsibility(ROUTERS/Brouters/Layer3 Switches) etc use them
c. it uses broadcast address
I think so, RARP and ARP are broadcasts
d. it establishes network addresses
Nah , dont think so,again Path-Determination occurs at layer 3 not 2.
e. it provides access to the LAN media
yea.. ummm not sure on this.
g. it provides path selection for Internet work communication
Yes, Switch may use path selection and switching.
So my ans are:a,c,e,& g.
******************************
*****
what kind of address is 192.168.0.255 given a 24 bit mask (255.255.255.0)?
Dude ...
0000 0000 = 0 = class A (range is 0 - 127)
Make sure you take in to account the usable addresses.
1000 0000 = 128 = class B,
1100 0000 = 192 = class C, Most commonly used
1110 0000 = 224 = class D,
1111 0000 = 240 = class E...does exist sme whea!! .
aiigth i hope that helps,
l8r, | |
| jeff_j_black 2002-06-18, 9:22 am |
| Checking my fingers... network layer IS layer three! The original question did not mention routers, it specified the network layer.
which 4 functions are performed by the Network Layer of the OSI model?
A. It used a two part address (I think we all agree on this one?)
b. it maintains routing tables (Routing tables function at the network level.)
c. it uses broadcast address (I was under the impression that broadcast domain is physical, it seems to me this implies layer 2? routers actually seperate broadcast domains!)
d. it establishes network addresses (what other layer establishes network addresses?)
e. it provides access to the LAN media (Nope! Layer 2)
f. it provides media independence for upper layers (Nope! Layer 2)
g. it provides path selection for Internet work communication (Yup!) | |
| jeff_j_black 2002-06-18, 9:36 am |
| Cisco 640-607 Exam Prep Guide defines broadcast address in a table called "LAN MAC Address Terminology and Features" as "An address that means “all devices that reside on this LAN right now.”"
All of this is under the heading "Data Link Function 2: Addressing"
So I conclude that broadcast address is a layer two function. | |
| jeff_j_black 2002-06-18, 10:58 am |
| The question of what kind of address is 192.168.0.255 /24, is answered:
It is a broadcast address. As such a packet directed to that address, would be routed to a single lan, where the broadcast would be broadcast to every node on that particular broadcast domain (Layer 2). A broadcast sent to that address would not be routed to every interface, just the one that is attached to that subnet address, so the broadcast address is not used at layer 3, it is used at layer 2. | |
| zzn169 2002-06-18, 9:44 pm |
| Okay, let's slow it up a bit. This question I am sure has been worded pretty tricky but here goes.
(Let's assume we are talking layer 3 and use the true or false method)
which 4 functions are performed by the Network Layer of the OSI model?
A. It used a two part address
(True; network:host)
b. it maintains routing tables
(True;Routing tables function at the network level; IP address mapping)
c. it uses broadcast address
(Tricky but TRUE;Explanation: Where does data start? From the top of the OSI and work down. In essence, if a broadcast address is formed, it will be formed from the network number and the mask as the data works its way down to layer 2)
d. it establishes network addresses
(True;Network addresses, layer 3)
e. it provides access to the LAN media (Nope! Layer 2)
f. it provides media independence for upper layers
(False;Media Access Layer for media indep. Layer 2)
g. it provides path selection for Internet work communication
(False; Path selection is done by STP and sometimes OSPF but we are still talking CCNA which only includes STP; Layer 2)
Those are my thoughts on the subject! | |
| sunney1234 2002-06-18, 9:59 pm |
| which 4 functions are performed by the Network Layer of the OSI model?
I also think its A,B,D and G
A. It used a two part address
(True; network:host)
b. it maintains routing tables
(True;Routing tables function at the network level; IP address mapping)
c. it uses broadcast address
(False: Because if the router will use the broadcast address then it will flood the data to all the ip address within the given subnet)
Switches use broadcast addresses once they can't find an address in their mac-table...
d. it establishes network addresses
(True;because it provides logical addressing which is also known as network address or hirec3)
e. it provides access to the LAN media (Nope! Layer 2)
f. it provides media independence for upper layers
(False;Media Access Layer for media indep. Layer 2)
g. it provides path selection for Internet work communication
(True; This gets done by routing protocols such as rip, igrp, ospf, ibgp, ebgp or static routes.)
Those are my thoughts on the subject! | |
| zzn169 2002-06-18, 10:26 pm |
| You have put me in my place on a couple of those! Here is a site that also confirms you comments and validates your answers and NOW my eyes are open. Thanks!
http://www.certifyexpress.com/cisc/ccna640-607/ccna640-607-cramnotes.pdf | |
| sunney1234 2002-06-18, 11:01 pm |
| You are welcome. I am very to know that my very 1st post was helpful.
-sunney | |
| sunney1234 2002-06-18, 11:02 pm |
| happy =): | |
| jeff_j_black 2002-06-19, 9:37 am |
| Welcome Sunney'. Nice points!
For every one who has issues with OSI layers 2 and 3, just remember, 2 is physical based addressing (burned in addresses, connected using ethernet, token ring and others.), 3 is logical based addressing (Addresses include network group and host id, routing logic and protocols work here.) |
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