DHCP address reservation

[mickane]

We use a private network with NAT on Bordermanager.

DHCP has been set up on the Bordermanager server.

I have been asked to change several computers to reserved addresses.

After trying to create the reservation for a computer (Win98SE), it continues to renew its DHCP licence, even after releasing it.

After reading the help, I cannot make this work.

Example:

Network using the 10.1.10.1/16 - 10.1.10.254/16 (netmask of 255.255.0.0) for DHCP scope.
Client reservation added as 10.1.20.10/16 - appears under the DHCP (numerical order).

Host Info entered includes MAC address and network type.

I don't know what else I can say.

Any ideas? Thanks.

 

[salserocito]

Why are you using a 16 bit subnet mask (255.255.0.0)? Your DHCP scope represents 10.1.10.1 - 10.1.10.254, so why are youtrying to add a reservation for 10.1.20.x/16? I understand that when using a 16-bit mask you could communicate with this address, but I think this is where your problem is.

Do you really need a 16 -bit mask? Do you really need that many IP addresses for your network? How many devices are we talking about?

If you were to go to a 24-bit mask (255.255.255.0)...
First off, you would immediately cut down on the amount of broadcast traffic across your network. You would have a much more managable scope. You could use an IP Address from the scope as your reservation.

If you needed more than 255 IP Addresses, you could "supernet" your subnet mask as 255.255.254.0 (23-bit), which would give you 510 IP Addresses (255 x 2), or 255.255.252.0 (22-bit), which would give you 1020 IP Addresses (255 x 4).

Using a 24-bit (or supernetted) would be easier to manage and alot less costly to administer.

Good Luck!

 

[mickane]

Client connections to a database are filtered by IP address. The reserved addresses will be used within the school library and will have fewer permissions (maintaining the library computers for more academic purposes). We could use static IP addresses on these 8 machines however, learning how to properly configure DHCP now will allow more flexibility for the future.

A DHCP server should be able to handle multiple scopes, so I figured that the above mentioned configuration should not be a problem.

The 16 bit subnet mask was in existence when I walked in the door. As a rule of thumb - "If it 'aint broke, don't fix it".

I don't understand how changing the mask would reduce network broadcasts (???!). Do you have any info or links that you could share on this one?? We only have one router - leading outside the network.

In general, we could have been using a 24 bit subnet mask up until now. However, by using a 16 bit mask we actually have minimized administration as follows:
10.1.30.x = computer tech's IP testing range
10.1.40.x = comp. sci. teacher's testing range
10.1.50.x = Linux test boxes (i.e.: English teacher's pet project)
etc.
This has allowed us to "hand off" ranges of IP addresses for special projects, which keeps the staff happier, it is easy to follow (try explaining a supernetted network to an English teacher), all computers recognize each other as being on the same network, and there is still a great degree of organization.

Thanks for the reply, I notice that you make many valuable contributions to this group.

Once again,

Is there a way to cause a particluar computer to take a specific address from DHCP, rather than renewing its old lease. It would seem as though simply creating a reserved address outside of the DHCP scope is not enoungh.

Thanks,

Mike

 

[TheLad]

So you want a specific machine that is configured for DHCP to pick up the same IP address all the time? I cannot personally see a way of doing it via the DNS/DHCP Management Console, however you can load DHCPCFG on the server and do it the old way (I am sure it will work?)
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"It's true, its damn true!"
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[castlemp919]

Check out these TIDs:

http://support.novell.com/cgi-bin/search/searchtid.cgi?/10052612.htm

http://support.novell.com/cgi-bin/search/searchtid.cgi?/10064350.htm

 

[mickane]

Thank you all.

"TheLad" summed up my needs quite well. The solution was quite simple:

using the DNS/DHCP console:

1 (done) - create your DHCP range if needed
2 (done) - create the specific entry for the host, specifying 'manual' along with the MAC address
3 (oops) - make sure that there is no entry still existing in the automatic DHCP scope. This cannot simply be 'released' from the client, but must be deleted by the DNS/DHCP console.

Sometimes the answers are so simple ... in fact ... the usually are.

 

[castlemp919]

We do the same thing here -- a large subnet to work with (10.156.x.x) and assign ranges of IP addresses for categories of hosts:
printers 10.156.9.x
workstations-dhcp 10.156.6.x
network devices 10.156.8.x
etc.

To make a long story short, can several subnet objects be used to cover address ranges even though they are all part of the same subnet? I ask because I don't see a way to make address range objects permanent so that I can push down the default gateway and DNS settings.

For instance, can I create a subnet object for 10.156.9.0 with a subnet mask of 255.255.0.0 and make that Permanent and then create another subnet object for 10.156.6.0 with the same subnet mask of 255.255.0.0 and make that Timed?

Thanx

 

[TheLad]

At my site, we use (for example) 192.168.92.* through to 192.168.95.*. Subnets 92 through to 94 are assigned to DHCP. We have two scopes on two different servers.

For example:

Server one serves 192.168.92.1 to 192.168.93.128 using a subnet mask of 255.255.252.0.

Server two serves 192.168.93.129 to 192.168.94.254 again using a subnet mask of 255.255.252.0

192.168.95.* is left unscoped, but is used for servers/printers.

I don't really see the need to add in your permanent addresses, just your DHCP ranges. -----------------------------------------------------
"It's true, its damn true!"
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[castlemp919]

Thanks. I had done it the other way around -- made the subnet DHCP and then excluded the static address ranges. Doh!