[cisco-voip] suggested/best practices for DHCP settings on routers

[Ryan Ratliff]

> An address conflict occurs when two hosts use the same IP address. During address assignment, DHCP checks for conflicts using ping and gratuitous Address Resolution Protocol (ARP). If a conflict is detected, the address is removed from the pool. The address will not be assigned until the administrator resolves the conflict.

Yes it does.

-Ryan

On May 9, 2011, at 2:47 PM, Lelio Fulgenzi wrote:

thanks Ryan.

I'm looking through the on-line documentation now, I'll have to pay attention to that chapter.

do you know off-hand if the IOS dhcp server does a ping before assignment?

---
Lelio Fulgenzi, B.A.
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Cooking with unix is easy. You just sed it and forget it. 
                              - LFJ (with apologies to Mr. Popeil)


From: "Ryan Ratliff" <rratliff at cisco.com>
To: "Lelio Fulgenzi" <lelio at uoguelph.ca>
Cc: "cisco-voip (cisco-voip at puck.nether.net)" <cisco-voip at puck.nether.net>
Sent: Monday, May 9, 2011 2:37:30 PM
Subject: Re: [cisco-voip] suggested/best practices for DHCP settings on routers

Look into the dhcp database configuration so you can keep your bindings on reload.
http://www.cisco.com/en/US/docs/ios/ipaddr/configuration/guide/iad_dhcp_svr_cfg.html#wp1061906

-Ryan

On May 9, 2011, at 2:25 PM, Lelio Fulgenzi wrote:

For our two remote campuses, I'm running DHCP for the phones on the local router rather than using our central DHCP server. This is causing us a few problems, namely when we reboot the router.

When we reboot the router, DHCP all bindings are lost, so when a phone is going through it's DHCP lifecycle, it's getting a different IP address and causing phones to reboot due to IP address conflicts.

I also just found out that I can't ping the phones from the router from the command line, so I'm guessing any ping before binding is failing, but I'm not sure the router does a ping before a bind.

'm leaning towards using the on-campus DHCP service, but am worried that in an extended down time the phones will crap out, especially during any sort of power cycle.

Anyone have any suggestions? I'm going to take a read through the online docs for v15 to see if there is anything available.


---
Lelio Fulgenzi, B.A.
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Cooking with unix is easy. You just sed it and forget it. 
                              - LFJ (with apologies to Mr. Popeil)


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