[c-nsp] Cisco IOS DHCP server problem

[Dionisios Karopoulos]

Hello,

Try disabling cdp/lldp towards the ip phone and see if it helps.

Kind Regards,
Dennis


-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of 
Michael Ulitskiy
Sent: Monday, August 7, 2017 10:06 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Cisco IOS DHCP server problem

Hello,



I'm sorry to ask such a probably basic question, but I'm at loss.

I have a very trivial setup: router (3825, IOS 15.0(1)M10) - switch (3750, IOS 
12.2(50)SE5) - ip phone (7962, firmware SCCP42.9-3-1SR3-1S)

For some reason the phone can't get ip address and I have no clue why. It 
looks like it discards router's DHCPOFFER.

Here's what I'm getting in debugging after phone powering up:



c199-41133#

Aug  7 14:35:50: DHCPD: client's VPN is .

Aug  7 14:35:50: DHCPD: DHCPDISCOVER received from client 010c.d996.9043.99 on 
interface GigabitEthernet0/0.20.

Aug  7 14:35:50: DHCPD: Sending DHCPOFFER to client 010c.d996.9043.99 
(10.10.15.38).

Aug  7 14:35:50: DHCPD: broadcasting BOOTREPLY to client 0cd9.9690.4399.

c199-41133#

Aug  7 14:35:54: DHCPD: client's VPN is .

Aug  7 14:35:54: DHCPD: DHCPDISCOVER received from client 010c.d996.9043.99 on 
interface GigabitEthernet0/0.20.

Aug  7 14:35:54: DHCPD: Sending DHCPOFFER to client 010c.d996.9043.99 
(10.10.15.38).

Aug  7 14:35:54: DHCPD: broadcasting BOOTREPLY to client 0cd9.9690.4399.

c199-41133#

Aug  7 14:36:02: DHCPD: client's VPN is .

Aug  7 14:36:02: DHCPD: DHCPDISCOVER received from client 010c.d996.9043.99 on 
interface GigabitEthernet0/0.20.

Aug  7 14:36:02: DHCPD: Sending DHCPOFFER to client 010c.d996.9043.99 
(10.10.15.38).

Aug  7 14:36:02: DHCPD: broadcasting BOOTREPLY to client 0cd9.9690.4399.



The config is very basic, subnet is directly attached, no dhcp relays:



Router:

ip dhcp pool DHCP-VOIP

   network 10.10.15.0 255.255.255.0

   default-router 10.10.15.1

   dns-server 10.10.15.1

!

interface GigabitEthernet0/0.20

description VOIP VLAN

encapsulation dot1Q 20

ip address 10.10.15.1 255.255.255.0

no ip redirects

no ip proxy-arp

ip verify unicast source reachable-via rx 1

ip nat inside

ip virtual-reassembly

!



Switch:

interface FastEthernet2/0/8

description Universal computer/phone port

switchport access vlan 10

switchport mode access

switchport voice vlan 20

spanning-tree portfast



I did some googling, I found several people complaining about similar problem, 
but no solution.

Does anyone have any idea what might be wrong here or how to further 
troubleshoot it?

Thanks a lot,



Michael



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