11-04-2008 04:47 PM - edited 03-06-2019 02:18 AM
Hi everyone,
I am having trouble getting DHCP to work across a trunk port. I have configured DHCP pools for voice and data on a Cisco 2811 router. I have on of the routers FastEthernet 1/3 ports connected to a port 0/23 on a Cisco 2960 switch. On the router I have configured the following on the router:
no ip dhcp use vrf connected
ip dhcp excluded-address 192.168.10.2
ip dhcp excluded-address 192.168.1.2
ip dhcp excluded-address 192.168.10.1
ip dhcp excluded-address 192.168.1.1
ip dhcp excluded-address 192.168.1.3
ip dhcp excluded-address 192.168.10.3
!
ip dhcp pool voice
network 192.168.10.0 255.255.255.0
default-router 192.168.10.2
option 150 ip 192.168.10.2
!
ip dhcp pool Data
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
!
interface FastEthernet1/3
switchport access vlan 233
switchport mode trunk
switchport voice vlan 10
interface Vlan1
ip address 192.168.1.2 255.255.255.0
!
interface Vlan10
ip address 192.168.10.2 255.255.255.0
!
interface Vlan233
ip address 192.168.233.43 255.255.255.0
On the 2960 switch I have the following configured:
switchport access vlan 233
switchport trunk allowed vlan 1,10,233
switchport mode trunk
interface Vlan1
ip address 192.168.1.1 255.255.255.0
no ip route-cache
!
interface Vlan10
description VOICE
ip address 192.168.10.1 255.255.255.0
no ip route-cache
!
interface Vlan233
ip address 192.168.233.41 255.255.255.0
interface FastEthernet0/1
switchport access vlan 20
switchport mode access
switchport voice vlan 10
When I plug an IP phone into FastEthernet 1/0 which gets is supposed to get an IP address via DHCP it never receives an IP address. How do you get DHCP to work across a trunk port?
Also when configuring the switch on the 2811 router I had to add all VLANS to the trunk I wasnt able to specify VLANS 1, 10 and 233 like I was on the switch.
11-04-2008 04:59 PM
Niall,
You need to use the "ip helper-address" statement on your 2960 uplink to the router. This will direct all DHCP requests to the DHCP server. Please follow the example below.
interface fa0/1
ip helper-address 192.168.1.1
HTH,
Mark
11-04-2008 05:13 PM
Scratch that....
Rereading the post I realized that is not the correct answer.
Have you created the layer 2 vlan on the 2960 switch?
switch(config)#vlan 10
If possible please post the configs for the switch and the router.
Mark
P.S. Is FastEthernet1/3 on your router the uplink to the switch? I would take out the "switchport access vlan 233" and "switchport voice vlan 10" if that is the case.
11-04-2008 05:35 PM
11-04-2008 05:34 PM
Hi niall,
C2960 is a L2 switch, hence, only 1 VLAN interface will be reflected up/up.
On the router (where it is doing L3), you might wish to try specify ip helper-address on the VLAN interfaces (1,10,233).
11-04-2008 10:48 PM
Hi ,
Could you double check if the DHCP service is running on the router.
use command service dhcp to start the services.
Chao
Vishwa
11-04-2008 11:08 PM
You need to change few configs in order proper troubleshoot the issue.
1. Please configure the port Fa 1/3 i.e the trunk port on the router as below :
interface FastEthernet1/3
switchport mode trunk
REMOVE THE FOLLOWING :
switchport access vlan 233
switchport voice vlan 10
2. Enable DHCP service on the router :
Config t# service dhcp
3. Check if you have a PC connected to the IP phone and its getting an IP address from Vlan 20.
Also remove "switchport access vlan 233" from Fa0/23 port.
Also, Please paste " show interface fa 0/23 switchport " from Switch and Show interface Fa 1/3 switchport " from the router.
-amit singh
11-05-2008 03:29 AM
The following have been removed:
switchport access vlan 233
switchport voice vlan 10
Here is the info for Fa0/23
Switch#show interfaces fastEthernet 0/23
FastEthernet0/23 is up, line protocol is up (connected)
Hardware is Fast Ethernet, address is 0018.738a.4d17 (bia 0018.738a.4d17)
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, media type is 10/100BaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:01, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 1000 bits/sec, 2 packets/sec
5 minute output rate 19000 bits/sec, 26 packets/sec
147665 packets input, 10715054 bytes, 0 no buffer
Received 147293 broadcasts (147001 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 147001 multicast, 0 pause input
0 input packets with dribble condition detected
1548378 packets output, 139336093 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 PAUSE output
0 output buffer failures, 0 output buffers swapped out
11-05-2008 03:32 AM
Please paste the output of this command :
Switch#show interfaces fastEthernet 0/23 switchport --> Please put switchport at the back of it...
Paste it from the router as well.
11-05-2008 03:46 AM
Ok so its kind of working now. If I plug a PC in it gets an IP but the phone isnt so i will have to check my phone and call manager and dhcp voice pool settings. Thanks for the help.
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