[c-nsp] Cisco IOS DHCP server problem

[Michael Ulitskiy]

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