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wirelessdog
join:2008-07-15
Queen Anne, MD

wirelessdog

Member

DHCP Question

Is there a way to tell the DHCP server to assign the same IP address after a lease expires unless it has some compelling reason to not give the same IP again?

tubbynet
reminds me of the danse russe
MVM
join:2008-01-16
Gilbert, AZ

2 recommendations

tubbynet

MVM

said by wirelessdog:

Is there a way to tell the DHCP server to assign the same IP address after a lease expires unless it has some compelling reason to not give the same IP again?

dhcp is first-come, first-serve.
you can do infinite leases, dhcp reservations -- but you can't make a pool that says "well -- keep these available for someone else who has used them unless you can't".

q.
public
join:2002-01-19
Santa Clara, CA

public to wirelessdog

Member

to wirelessdog
said by wirelessdog:

Is there a way to tell the DHCP server to assign the same IP address after a lease expires unless it has some compelling reason to not give the same IP again?

That would be option 50.
wirelessdog
join:2008-07-15
Queen Anne, MD

wirelessdog

Member

???

KA0OUV
Premium Member
join:2010-02-17
Jefferson City, MO

KA0OUV to wirelessdog

Premium Member

to wirelessdog
I believe if you use a manual binding, you can accomplish that.

»www.cisco.com/c/en/us/td ··· p1001108
JoelC707
Premium Member
join:2002-07-09
Lanett, AL

JoelC707 to wirelessdog

Premium Member

to wirelessdog
»wiki.snom.com/Networking ··· dress.29

I've never used it so I can't help you configure it but it sounds like what you want to do. It kinda sounds like DHCP reservations though, otherwise, how would option 50 work, or does it only come into play AFTER the initial DHCP assignment?

DaSneaky1D
what's up
MVM
join:2001-03-29
The Lou

1 recommendation

DaSneaky1D to wirelessdog

MVM

to wirelessdog
Can you share with us what the bigger picture is? Maybe an alternative solution can be suggested to help get to the desired end result.
HELLFIRE
MVM
join:2009-11-25

HELLFIRE to wirelessdog

MVM

to wirelessdog
2nd tubbynet See Profile and DaSneaky1D See Profile entirely... just as a dumb question, are you using a Cisco IOS device
as a DHCP server, or is this just a question about DHCP in general?

For DHCP option 50, I suggest you read over this link -- for a deeper explanation, and if you've a case of insomnia, I'd suggest going to the RFCs

My 00000010bits

Regards
wirelessdog
join:2008-07-15
Queen Anne, MD

wirelessdog

Member

said by HELLFIRE:

re you using a Cisco IOS device
as a DHCP server

Yes.
wirelessdog

wirelessdog to DaSneaky1D

Member

to DaSneaky1D
said by DaSneaky1D:

Maybe an alternative solution can be suggested to help get to the desired end result.

The alternate solution is reservations. I'm just lazy.

There are ISP's that assign the same IP address to the customer via DHCP unless the customer's MAC address changes.

Perhaps they are running some script that creates a reservation post-DHCP lease.

I was hoping for an option within the DHCP server to accomplish the end result without manual intervention.
markysharkey
Premium Member
join:2012-12-20
united kingd

markysharkey

Premium Member

Manipulating the DHCP server doesn't count as manual intervention?

The options you want are DHCP reservations or simply set static IP's to the devices and remove them from the DHCP Pool. Should take about 30 secs on the CLI to remove an address or range of addresses from the DHCP pool. Setting up static IP's on the hosts shouldn't be too difficult. Setting up DHCP Option 50 on the hosts may more labour intensive but I don't know 'cos I've never had to.
wirelessdog
join:2008-07-15
Queen Anne, MD

wirelessdog

Member

30 seconds x 1,000 devices. Setting up anything on the client is labor intensive. I was hoping for a way to set it up on the server.
markysharkey
Premium Member
join:2012-12-20
united kingd

markysharkey

Premium Member

Whichever way you shake it, managing 1,000 devices is going to take time. It seems option 50 is out which leaves you with reservations on the DHCP server and setting static IP's on the devices, or you will have to create 1,000 DHCP reservations. I don't see any other way to do this with an IOS device as the DHCP server.
If your devices are grouped by IP address that could alleviate some of the config overhead, but other than that it sounds like you're in for a long spell at the keyboard.
wirelessdog
join:2008-07-15
Queen Anne, MD

wirelessdog

Member

Thanks, that gives me an answer I can deal with. The headache associated with devices changing IP address is less than entering reservations. I was just hoping my ios device could be a little more intelligent than it is capable of.
HELLFIRE
MVM
join:2009-11-25

1 recommendation

HELLFIRE to wirelessdog

MVM

to wirelessdog
said by wirelessdog:

said by HELLFIRE:

re you using a Cisco IOS device as a DHCP server

Yes.

...then you should be aware that the option(s) in IOS DHCP are very very limited. Configure the pool,
configure the DG, configure the DNS server, configure a MAC address... and from a scalability perspective
not sure if IOS DHCP should be used if you have 1000hosts in total.
said by wirelessdog:

Perhaps they are running some script that creates a reservation post-DHCP lease.

EEM perhaps? Can't give you the exact command(s) though...

My 00000010bits

Regards

DaSneaky1D
what's up
MVM
join:2001-03-29
The Lou

DaSneaky1D to wirelessdog

MVM

to wirelessdog
Are you looking for this "sticky" IP addressing for end users or infrastruture?
wirelessdog
join:2008-07-15
Queen Anne, MD

wirelessdog

Member

Both

DaSneaky1D
what's up
MVM
join:2001-03-29
The Lou

DaSneaky1D

MVM

For your infrastructure, I would suggest assigning the IPs via MAC address. It is slightly manual, as you'd have to initially set it up, but it will keep the same IP assigned each time.

I don't have a suggestion for end users besides providing each one a static IP address.