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Home > Archive > CCNA > February 2002 > Network Layer
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| JayDot 2002-02-11, 6:15 pm |
| Ok The Network Layer has 4 Characteristics
1)
Two Part Adressing ??
is that Source & Destination?
2)
Responsible for Route Table
got this, Hold routing tables
3)
Best Path Selection
selects best path if dynamic
4)
Track Device Location ??& Use Broadcast Address??
Troy Tech Page 1 OSI Model Network Layer
Page#2 Keypoints | |
| JayDot 2002-02-11, 6:49 pm |
| This is A Question I'm asking
Although it may not seem So...
Could someone Help Me Out~ | |
|
| OK. I will try my best
1. Two parts addressing. That is network portion and host portion. Let's say IP. IP address has two parts using subnet mask to divide the address. Two IP address with the same network portion will belong to the same network.
2. Responsible to the routing table. This is obvious. Each network-layer operating device will hold the routing table. Each incoming packet's destination address will be compare against the routing table. The output from this comparison is the outgoing interface and next hop address.
3. Best path selection. This is again obvious. In case we have a multiple path to reach the same destination, routing (layer 3) will be responsible for the path selection. The routing protocol e.g. RIP,IGRP,OSPF will select the best path based on metric. For example, RIP use hop count as a metric, then the shortest path will be selected as a best path regardless to bandwidth.
4. Track device location and using broadcast address. I'm not sure what are you talking about, but I think that this is a routed protocol e.g. IP, IPX responsibility.
When packet are routed to the last hop, the last router must ship this packet to the destination host. Looking at the host portion of the network address, the router can determine the layer2 address by looking at the Layer 3 to Layer 2 mapping table. This should be a "track device location". In case the table has no the L3-L2 mapping entry corresponse to the packet, it will send a broadcast packet out in the destination segment asking for the destination host to send back its L2 address. This is how ARP come into play. | |
| JayDot 2002-02-12, 8:10 am |
| Hoon~
Thanx... That was Well Explained
Cleared it up Completly and added to my overall understanding of other areas... |
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