IP reservation in Window 2008 DHCP

AXISHK used Ask the Experts™
I have reserved few IPs for some phone device. In Window DHCP, it shows "inactive". What does it mean ?

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Thomas GrassiSystems Administrator

Inactive means the device has not contacted the DHCP server yet.

What type of phones are these?

iPhones change the mac addresses dynamically for security reasons.
Senior Information Technology Consultant
See, this matters depending on type of phone.  Are we talking IP Phone like Scope Option 125 such as with Mitel or SIP?  How do you know the static IP is reserved?  Is it just an open scope for example?

With VOIP you have dedicated VLAN or subnetwork.

And this depends on intra-VLAN routing where multiple subnets exist a single VLAN.  Bad idea if you are “supernetting” or “Super Scope”.  

Just in general, you should look into putting VOIP phones into their own VLAN or subnetwork.  Once you have them on their own IP scheme, then you won't have to worry about any other DHCP clients other than phones in the same pool.  Now this might change if you use pass-through phones.  

When a VOIP phone starts up, it doesn't know what VLAN to use or “untagged”.  Your DHCP server would give a response that includes a 125 option with relative information.  Any original address it had is released and new lease established.

Regarding “Inactive”.

Is your SCOPE, Inactive?

Or does the IP Address show, “Inactive”

Is there a “Computer” connected to the phone using a pass-through port?

Is that PORT using “In-line power”?

The phones also usually have computers connected to a pass-through port. The packets from the computers are never tagged, and so the PCs will stay on the original (untagged) VLAN for the port.



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