URGENT requirement!!!!locking the ip address to a particular MAC

By mohdanwarahmed ·
Hi all....

Aim: Ip address lets say when assigned to a particular MAC let it be pc, should not be used by any other mac, even if i switch off the device.

I tried through dhcp reservation option which maps the ip address to a mac address, it works. but the problem is, when i switch off the pc, this ip address can be used on the other machine(pc).

Is there any such solution in microsoft dhcp or else can we do it through the cisco router???? If any please give me the detail procedure.

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All Answers

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Set the lease...

by Breezer85 In reply to URGENT requirement!!!!loc ...

Best thing to do is set the lease to the maximum numbers of days, or even better assign the machine this ip address as static!

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if i set the static ip add

by mohdanwarahmed In reply to Set the lease...

if i set the static ip add, ofcourse when i will shut my system down, the other pc can use ip address of mine, which i dont want.

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Another option

by Churdoo In reply to URGENT requirement!!!!loc ...

In MS DHCP, if your desired IP address is NOT within the address pool it will not get assigned to other clients, yet it CAN be used in a reservation.

In other words in your example, if your address pool is say -, will not be leased to any general clients, however can be used in a reservation and will be assigned to the appropriate client with the matching MAC address.

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Thanks for posting..

by mohdanwarahmed In reply to Another option

hi churdoo,

As you said, if we exclude the ip from the pool and reserve the ip to the mac add, it would work, but WHEN I SWITCH OFF MY PC,the clients may statically or manually configure the same ip on the pc and still can use.

Please explain if i m wrong.
and also if there is a solution which can be done from the cisco router configuring dhcp, please let me know.

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There should be

by tmalo627 In reply to Thanks for posting..

Most higher end routers, especially a Cisco, should have a section to reserve IP addresses to a specific MAC. Sometimes it's referred to as Static DHCP. Simply put in the MAC address and the IP address you want to match up and it should take care of the rest for you.

Also to touch on another poster's idea through MS if the address is not in the address pool, it won't get assigned. If you're saying you have the reservation set and that address is still be given out, there may be another device performing the DHCP service somewhere in your network. A good way to test that is to go to the machine that is picking up the IP address it shouldn't have and run IPCONFIG /ALL. See what it says for DHCP server. That will tell you the device issuing the address.

Hope this helps.

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Just out of curiousity...

by Breezer85 In reply to URGENT requirement!!!!loc ...

...Why does this machine have to have this IP address. Surely if you've got a DHCP server which assigns an IP you'll still get connected!

Also, when you set the lease to 365 days and switch the machine off, that IP WILL stay with that machine and no other. Beacause all other machines will not query for an IP until after the 365 day lease time expires!

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Probably because

by Brenton Keegan In reply to Just out of curiousity...

Probably because he's doing this on his workstation. It sounds like to me he's created an ACL that restricts traffic, but he wants his workstation to have a different level of access than the other workstations. So he has to specify a specific IP.

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Agreed, and not only that; when the cat's away?

by Churdoo In reply to Probably because

I agree it sounds like he's got an ACL which allows special access for the IP in his example, but the problem isn't so much "How do you assign this IP addy to this specific workstation?";
rather the second part of the problem is, "how does he keep others, once they learn of the special access for IP, from assigning themselves this IP statically and giving themselves this access when the cat's away?"
I don't know how to do this in Cisco gear, though I'm no Cisco powerhouse by any stretch of the imagination.

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hey breezer!!!

by mohdanwarahmed In reply to Just out of curiousity...

thanks for your postings!!

seems your idea of setting the lease wud work out as u said that other pcs cannot access with the ip address when my pc is shut.
can u give me the procedure of how to lease an ip address in dhcp environment...gimme the exact steps so that i can do it easily....!!!

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Lease Time Steps...

by Breezer85 In reply to hey breezer!!!

Start - Admin Tools - DHCP - Expand the server tab - Right click 'Scope...' - Properties - General Tab - Change the lease time.

I would much prefer to do it this way than trying to mess about with different solutions! My theory is to keep it short, sweet and simple!

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