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Old 02-12-08, 01:20 PM   #2
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Join Date: Feb 2008
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Default Re: 2 Network Segments on 1 Switch

Originally Posted by fivefeet8
I have a question for anyone who's a networking expert.

How come you can use 1 switch for 2 network segments? Is it because of the protocol used? Is it by design? Also, what if both segments have their own DHCP server? How would the switch handle the assignment of DHCP address allocation per segment?

well first off you need to understand osi modeling
well not to get to heavy into tcp/ip if you look at the diagram on that wiki a switch operates at layer 2 and ip addressing operates at layer 3. when you have two protocals operating at two seperate layers, they dont know anything about each other, so a switch cannot see the ip addresses at layer 3. it knows nothing about it. so you can have hunreds of diferent networks on a single switch and that switch wouldnt know any diffrent becuase it cannot read layer 3.

ok about dhcp, dhcp works on layer3 address assignments and a switch cannot see what the dhcp server or servers are doing because a switch knows nothing about layer 3 addressing. DHCP assigns layer 3 address to hosts. the address range allication is handle by defining the ip address range in the DHCP server, again the switch doesnt see anything. the DHCP handles all of it. now when you have multiple segments you will do something called "vlan", short for virtual lan. when you get into vlaning you segment the network by a port bases. so you can have ports 1 through 8 on vlan 1 with your first network segment and you can have ports 9 through 16 on vlan 2 with network ip address assignment of network 2. this will help with segmenting your networks.
i know i didnt do such a hot job of explaing it but this is a very deep issue that is something you study and work with over a long period of time
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