[cisco-voip] DHCP Problems | CME / Windows

Mon Mar 15 11:29:25 EDT 2010

What's strange is that the DHCP pool I set up for the phones is on a
private IP range that is unadvertised outside from the CME router.

On the router, I've defined the DHCP pool "phone" with the range of
10.10.10.0/24.  There is nothing specified in the ip routes on the CME.
On the switches connected to the network, the voice vlan goes to the
interface on the CME with the IP 10.10.10.1.

I don't see how in the debug log, how the PC even knows about the other
DHCP server if you can't even ping it or see it. 

Hyoun Kim

Network Administrator I

Charter Media - East Division

640 Broadmor Blvd, Suite 80

Murfreesboro, TN 37129

Email: Hyoun.Kim at chartercom.com

Office: 615.217.6245

Fax: 615.217.6255

From: Ryan Ratliff [mailto:rratliff at cisco.com] 
Sent: Thursday, March 11, 2010 3:17 PM
To: Chris Ward (chrward)
Cc: Kim, Hyoun S; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] DHCP Problems | CME / Windows

That debug tells me that the dhcp database on the router had a previous
entry for this client and is now seeing the request on a different vlan.

You can see that after the DHCPNak is sent it sees the request come in,
confirms it doesn't have a pool for that address range, and doesn't send
another Nak.  

I think you need to see the debugs that result in this client getting
into the dhcp database to begin with.

-Ryan

On Mar 11, 2010, at 4:03 PM, Chris Ward (chrward) wrote:

"010542: Mar 11 15:35:27.595 EST: DHCPD: client has moved to a new
subnet."

That doesn't seem good. Any ip-helpers in use here?

+Chris

From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Kim, Hyoun S
Sent: Thursday, March 11, 2010 3:41 PM
To: Ryan Ratliff (rratliff)
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] DHCP Problems | CME / Windows

I do have another router, but it doesn't point anything to the CME
router.   All I did was configure the CME router to use a valid IP
within the subnet.

Here is the output I've gotten so far:

010540: Mar 11 15:33:46.498 EST: DHCPD: checking for expired leases.

010541: Mar 11 15:35:27.595 EST: DHCPD: DHCPREQUEST received from client
0100.247e.1137.4c.

010542: Mar 11 15:35:27.595 EST: DHCPD: client has moved to a new
subnet.

010543: Mar 11 15:35:27.595 EST: DHCPD: Sending notification of
ASSIGNMENT FAILURE:

010544: Mar 11 15:35:27.595 EST:   DHCPD: htype 1 chaddr 0024.7e11.374c

010545: Mar 11 15:35:27.595 EST:   DHCPD: remote id
020a0000ac15c8c100000000

010546: Mar 11 15:35:27.595 EST:   DHCPD: circuit id 00000000

010547: Mar 11 15:35:27.595 EST: DHCPD: Sending notification of
ASSIGNMENT_FAILURE:

010548: Mar 11 15:35:27.599 EST:  DHCPD: due to: Reason with no text
explanation

010549: Mar 11 15:35:27.599 EST:   DHCPD: htype 1 chaddr 0024.7e11.374c

010550: Mar 11 15:35:27.599 EST:   DHCPD: remote id
020a0000ac15c8c100000000

010551: Mar 11 15:35:27.599 EST:   DHCPD: circuit id 00000000

010552: Mar 11 15:35:27.599 EST: DHCPD: Sending DHCPNAK to client
0100.247e.1137.4c.

010553: Mar 11 15:35:27.599 EST: DHCPD: broadcasting BOOTREPLY to client
0024.7e11.374c.

010554: Mar 11 15:35:28.623 EST: DHCPD: Sending notification of
DISCOVER:

010555: Mar 11 15:35:28.623 EST:   DHCPD: htype 1 chaddr 0024.7e11.374c

010556: Mar 11 15:35:28.623 EST:   DHCPD: remote id
020a0000ac15c8c100000000

010557: Mar 11 15:35:28.623 EST:   DHCPD: circuit id 00000000

010558: Mar 11 15:35:28.623 EST: DHCPD: DHCPDISCOVER received from
client 0100.247e.1137.4c on interface FastEthernet0/0.

010559: Mar 11 15:35:28.623 EST: DHCPD: Seeing if there is an internally
specified pool class:

010560: Mar 11 15:35:28.623 EST:   DHCPD: htype 1 chaddr 0024.7e11.374c

010561: Mar 11 15:35:28.623 EST:   DHCPD: remote id
020a0000ac15c8c100000000

010562: Mar 11 15:35:28.623 EST:   DHCPD: circuit id 00000000

010563: Mar 11 15:35:28.623 EST: DHCPD: there is no address pool for
172.24.200.193.

010564: Mar 11 15:35:28.651 EST: DHCPD: DHCPREQUEST received from client
0100.247e.1137.4c.

010565: Mar 11 15:35:28.651 EST: DHCPD: no subnet configured for
172.24.217.73.

010566: Mar 11 15:35:28.651 EST: DHCPD: Finding a relay for client
0100.247e.1137.4c on interface FastEthernet0/0.

010567: Mar 11 15:35:28.651 EST: DHCPD: Seeing if there is an internally
specified pool class:

010568: Mar 11 15:35:28.651 EST:   DHCPD: htype 1 chaddr 0024.7e11.374c

010569: Mar 11 15:35:28.651 EST:   DHCPD: remote id
020a0000ac15c8c100000000

010570: Mar 11 15:35:28.651 EST:   DHCPD: circuit id 00000000

010571: Mar 11 15:35:28.651 EST: DHCPD: there is no pool for
172.24.200.193.

010572: Mar 11 15:35:46.500 EST: DHCPD: checking for expired leases.

That MAC address is a PC.

Hyoun Kim

Network Administrator I

Charter Media - East Division

640 Broadmor Blvd, Suite 80

Murfreesboro, TN 37129

Email: Hyoun.Kim at chartercom.com

Office: 615.217.6245

Fax: 615.217.6255

From: Ryan Ratliff [mailto:rratliff at cisco.com] 
Sent: Thursday, March 11, 2010 11:48 AM
To: Kim, Hyoun S
Cc: cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] DHCP Problems | CME / Windows

debug dhcp detail
debug ip dhcp server event
debug ip dhcp packet

I don't believe the ios dhcp server will attempt to serve requests on an
interface it doesn't have a dhcp pool defined for.  Do you happen to
have another router with a data vlan address and ip-helper pointed to
the CME router?

-Ryan

On Mar 11, 2010, at 12:21 PM, Kim, Hyoun S wrote:

After implementing the last Cisco VoIP solution for our offices, I've
stumbled across a problem with machines (all Windows) that occasionally
drop their network connection just briefly every couple of hours.  While
this normally wouldn't be a problem, it is for us because we redirect
several of the default Windows folders to a Windows server.  When the
connection drops, Windows loses these folders and you have to log
off/log on to get them back.

Looking into the Event Properties of various windows machines, it
intermittently gets a DHCPNACK message from another DHCP server.
Unfortunately, that DHCP server is the DHCP pool I set up on the CME.

One of the Ethernet ports on the CME is configured for the data VLAN.
This is connected to our switch with only the data VLAN being shown when
I perform a show spanning-tree on that interface.

The other Ethernet port is strictly configured for the voice VLAN and
displays only the voice VLAN in a show spanning-tree on that interface.

Each PC port has both the data VLAN & voice vlan defined in the
configuration w/ the phone containing "switchport voice vlan 100".

Do you guys have any suggestions on why the Windows machines are trying
to pull an IP from the Cisco DHCP server I set up for the phones?

Thanks in advance.

<image001.jpg>

________________________________

Hyoun Kim * Network Administrator I - East Division

640 Broadmor Blvd * Suite 80 * Murfreesboro, TN 37129

' 615.217.6245 * ' 859.312.6941 * 7 615.217.6255 * *
Hyoun.Kim at chartercom.com

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