[cisco-voip] DHCP Behavior

Lelio Fulgenzi lelio at uoguelph.ca
Thu Jun 7 09:45:31 EDT 2007


But the phone has the IP address of the DHCP server - so it will try to communicate directly. Unless the scope or server is stopped.

Ok, maybe two minutes is a bit harsh, 5 minutes should be ok. we did this on a network of about 7500 and it was not a problem over the 5 days in order to let them old leases expire.

As they get to the new lease from the new DHCP server they get the longer lease.


--------------------------------------------------------------------------------
Lelio Fulgenzi, B.A.
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
"Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo."      WJR

  ----- Original Message ----- 
  From: Matt Slaga (US) 
  To: Lelio Fulgenzi ; Ed Leatherman ; ciscovoip 
  Sent: Thursday, June 07, 2007 9:39 AM
  Subject: RE: [cisco-voip] DHCP Behavior


  If you are not changing IP networks, then you can leave them the way they are and let them change DHCP servers on their own.  If you set it to 1 minute, every phone will be requesting a new address every 30 seconds which would have a negative impact on users.

   

  Let them migrate on their own over a few days.  The phones don’t care what the dhcp server is, as long as one responds.

   

  From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Lelio Fulgenzi
  Sent: Thursday, June 07, 2007 9:35 AM
  To: Ed Leatherman; ciscovoip
  Subject: Re: [cisco-voip] DHCP Behavior

   

  I would set the lease time to about 2 minutes for a migration like this.

   

  Typically, lease renewals happen 1/2 way through the lease time.

   

  The new DHCP server should ping the address before it assigns it, but you might get IP address conflicts. In that case, the phone reboots and tries to get a new address.

   

  --------------------------------------------------------------------------------
  Lelio Fulgenzi, B.A.
  Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
  (519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 
  "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo."      WJR

    ----- Original Message ----- 

    From: Ed Leatherman 

    To: ciscovoip 

    Sent: Thursday, June 07, 2007 9:31 AM

    Subject: [cisco-voip] DHCP Behavior

     

    I'm getting ready to start migrating ip phones off of the DHCP service on our callmanager to a DHCP appliance (infoblox). I've got the lease timer down to 1 hour now on my first set of phones, my next step is going to be to change the ip helper-address on the routers and deactivate the scope in DHCP on the windows box. 

    How do the phones behave when they try to renew and their original DHCP server isnt there? Do i need to reset all of them, or will they find the new server on their own? 

    -- 
    Ed Leatherman
    Senior Voice Engineer
    West Virginia University
    Telecommunications and Network Operations 


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