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Home > Archive > 70-216 > January 2003 > DHCP question
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| drhixson 2003-01-16, 9:07 pm |
| I am still a little fuzzy on DHCP reservations and exclusions. When do you use one and not the other? MS press states to use reserverations for other DHCP servers, diskless workstations, RRAS, and exclusions for printers, etc. I just dont understand "why" one and not the other. Can anyone shed some light on this? | |
| Slinky 2003-01-16, 9:21 pm |
| Reservations use MAC addresses to lease IPs. Say you have 1 RRAS with a MAC address of 01-AB-12-CD-34-EF and you want it to always obtain an address of 192.168.1.1 from the DHCP server. The only way to guarantee that the server gets the same address is by creating a reservation with that MAC address. Basically you create these when you don't want the IP address to ever change, especially on servers.
Now for reservations, lets say that you have a DHCP scope of 192.168.1.1-192.168.1.254. You also have a pool of 5 network printers that are already preconfigured with the addresses of 192.168.1.10-192.168.1.14, so you'll want to exclude those addresses from the pool so the DHCP server doesn't lease them out to other clients. You could create two scopes, but thats the hard way of doing it when you could create 1 scope and then exclude those addresses.
Make sense or did I completely lose you?  | |
| drhixson 2003-01-16, 9:25 pm |
| sounds good, wouldnt it be easier for the administrator to hardcode the IP addresses on other servers and printers? | |
| Slinky 2003-01-16, 9:38 pm |
| Just from personal experience, I see more uses for exclusions rather than reservations. Typically servers have static IPs already and therefore don't obtain their address from DHCP servers, so you'll want to exclude those IPs from the pool and not reserve them. Know what I mean? | |
| jayjay22 2003-01-17, 12:20 am |
| I find it easier in practice to make the scope smaller when you want to assign static addresses. All of the servers I work with have static address that are outside the range of the DHCP scope we've set on each subnet, so there is no need for reservations or exclusions.
Just my 2 cents.... | |
| sb1815 2003-01-17, 1:36 am |
| you reserve an address you want DHCP to always give to a specific host.
you exclude an address you want DHCP to not do anything with. (a host with a static IP). | |
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| To assign a computer a static IP address, you can either do it at the individual computer or through a reservation on the DHCP server.
If you choose to configure static IP addresses at all nodes that you want to have a permanent address, you have to physically go to each machine and physically configure each machine. If they are then moved to another subnet, you have to reconfigure the machine at the box itself. Plus you have to maintain a list of all IP addresses you have used so you don't accidentally re-use one and cause a conflict. Also have to be sure you correctly enter the subnet mask, and gateway.
If you make reservations at a DHCP server and make each of your nodes (printers, servers, etc. that you want to have static IP addresses) a DHCP client, administration is easier: you can change IPs from your DHCP just by changing the reservation. DHCP server automatically issues the reserved IP address with appropriately configured mask and gateway. If one of your employees wants to move a printer from one area to another, they can do the physical moving and all you have to do is reconfigure the reservation at the DHCP server if it goes to another subnet.
You should assign the actual DHCP server a static IP address; no reservation. | |
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| a cool example on my enviroment:
option 1
dhcp scope 192.168.1.1 - 192.168.1.254
exclude 192.168.1.1 - 192.168.1.20
this allow to use from 1 to 20 for your gateway, firewall, routers, printers, servers, switchs, hubs, etc etc.... you need to configure all this units manually
option 2
dhcp scope 192.168.1.20 - 192.168.1.254
here you donīt need to exclude anything. only configure the units manually.
option 3
dhcp scope 192.168.1.1 - 192.168.1.254
reservation for all required units.
do you get the points?
excluded addresses is used when you want to exlude a ip address from one scope to been assigned. for example. in the option 1, if you add a printer with ip address 192.168.1.25 you need to exlude this ip address on the dhcp scope to prevent asignament of this address to a host.
you can make reservations when you want to provide the same ip address to specific host. for example, the boss of the bosses on my company use the public ip address 200.36.x.8 and i make a reservation for him, using their NIC mac address. everytime he get a ip address from the network, he get the same 200.36.x.8
hope this help.
iīm studyng for the BEAST design!
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| Rudeboy 2003-01-20, 1:12 am |
| Looking at cm2gj's post, I use option 2, have a smaller scope (192.168.1.20-254). Which option is the Microsoft way?
RB | |
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| quote:
Originally posted by Rudeboy
Looking at cm2gj's post, I use option 2, have a smaller scope (192.168.1.20-254). Which option is the Microsoft way?
RB
this is the recommended. option 2.
option 1 is very used too...... but option 2 is my prefered! | |
| Slinky 2003-01-20, 12:18 pm |
| Microsoft wants you to use exclusions. So thats the way you'll need to answer it for the exam. | |
| cm2gj 2003-01-21, 12:07 am |
| quote:
Originally posted by Slinky
Microsoft wants you to use exclusions. So thats the way you'll need to answer it for the exam.
exclusions is what this guys want to see in their exams as response......like active directory integrated zones..... etc! but i prefer option 2........sometimes.... |
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