topic Wireless DHCP problem in Wireless

Wireless DHCP problem

Kamran Mustafayev — Sun, 04 Jul 2021 04:47:49 GMT

Hello,

I have a problem

We have cisco ap 500 series, it was lightweight, but we migrate it to standalone, now, the scheme is simple.

We have a router 2811 and dhcp created on it, also we have f0/0.30 virtual interface with ip of 10.10.30.1

On switch one interface (trunk) goes to router f0/0 interface, and one interface (access) goes to ap

On AP we have BVI interface with 10.10.30.10, and default route to 10.10.30.1

So when we connecting to our SSID, it connect but doestn receive DHCP, and takes APIPA address, please explain why ap doesnt assign ip to clients

Also ap config.txt here

Thank you

Wireless DHCP problem

Justin Kurynny — Thu, 15 Mar 2012 06:16:30 GMT

Kamran,

Can you ping from the router to the AP? From the AP to the router?

Assuming your 2811's fa0/0.30 is encapsulation dot1q 30, is your switchport that your AP is connected to set to switchport access vlan 30?

Make sure VLAN 30 exists on your switch ((config)#vlan 30). You can have it assigned on a switchport, but if it doesn't exist in the VLAN database, no traffic will pass on VLAN 30.

Justin

Wireless DHCP problem

Kamran Mustafayev — Thu, 15 Mar 2012 06:23:08 GMT

Yep, Ping is going from ap to router and vice versa, fa0/0.30 also has encapsulation dot1q30

Ap connect to switchport with switchport access vlan 30

Vlan 30 in database

I dont understand why ap doesnt broadcast dhcp

Wireless DHCP problem

Justin Kurynny — Thu, 15 Mar 2012 06:28:51 GMT

Kamran,

Can you post the AP config? I think you tried to post it in your first message, but it didn't come through.

Justin

Wireless DHCP problem

Justin Kurynny — Thu, 15 Mar 2012 06:29:38 GMT

Kamran,

Also, the router config? Remove passwords, keys, etc. Thanks.

Justin

Wireless DHCP problem

Kamran Mustafayev — Thu, 15 Mar 2012 06:37:39 GMT

Here is AP configs:

show run

*Mar 1 00:25:26.377: %SYS-5-CONFIG_I: Configured from console by console

Building configuration...

Current configuration : 1607 bytes

version 12.4

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

service password-encryption

hostname ap

enable secret 5 $1$cFC2$NdW0rVFAwPMOIuKhfk6G1/

aaa new-model

aaa session-id common

dot11 vlan-name VLAN30 vlan 30

dot11 ssid VLAB

vlan 30

authentication open

guest-mode

power inline negotiation prestandard source

username Cisco

bridge irb

interface Dot11Radio0

no ip address

no ip route-cache

encryption mode ciphers aes-ccm

ssid VLAB

station-role root

bridge-group 1

bridge-group 1 block-unknown-source

no bridge-group 1 source-learning

no bridge-group 1 unicast-flooding

bridge-group 1 spanning-disabled

interface Dot11Radio0.30

encapsulation dot1Q 30

no ip route-cache

bridge-group 195

bridge-group 195 subscriber-loop-control

bridge-group 195 block-unknown-source

no bridge-group 195 source-learning

ap#

ap#show run

Building configuration...

Current configuration : 1607 bytes

version 12.4

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

service password-encryption

hostname ap

enable secret 5 $1$cFC2$NdW0rVFAwPMOIuKhfk6G1/

aaa new-model

aaa session-id common

dot11 vlan-name VLAN30 vlan 30

dot11 ssid VLAB

vlan 30

authentication open

guest-mode

power inline negotiation prestandard source

username Cisco

bridge irb

interface Dot11Radio0

no ip address

no ip route-cache

encryption mode ciphers aes-ccm

ssid VLAB

station-role root

bridge-group 1

bridge-group 1 block-unknown-source

no bridge-group 1 source-learning

no bridge-group 1 unicast-flooding

bridge-group 1 spanning-disabled

interface Dot11Radio0.30

encapsulation dot1Q 30

no ip route-cache

bridge-group 195

bridge-group 195 subscriber-loop-control

bridge-group 195 block-unknown-source

no bridge-group 195 source-learning

no bridge-group 195 unicast-flooding

bridge-group 195 spanning-disabled

interface FastEthernet0

no ip address

no ip route-cache

duplex auto

speed auto

bridge-group 1

no bridge-group 1 source-learning

bridge-group 1 spanning-disabled

interface FastEthernet0.30

encapsulation dot1Q 30

no ip route-cache

bridge-group 195

no bridge-group 195 source-learning

bridge-group 195 spanning-disabled

interface BVI1

ip address 10.10.30.10 255.255.255.0

no ip route-cache

ip default-gateway 10.10.30.1

ip http server

no ip http secure-server

ip http help-path http://www.cisco.com/warp/public/779/smbiz/prodconfig/help/eag

bridge 1 route ip

line con 0

line vty 0 4

end

and Router config:

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

hostname HQRTR

boot-start-marker

boot-end-marker

card type e1 0 0

logging message-counter syslog

no aaa new-model

memory-size iomem 10

clock timezone AZT 4

network-clock-participate wic 0

dot11 syslog

ip source-route

ip cef

ip dhcp excluded-address 10.10.30.1 10.10.30.10

ip dhcp excluded-address 10.10.20.1 10.10.20.10

ip dhcp pool HQPHONES

network 10.10.30.0 255.255.255.0

default-router 10.10.30.1

option 150 ip 10.1.200.101 10.1.200.102

no ip domain lookup

no ipv6 cef

multilink bundle-name authenticated

isdn switch-type primary-net5

voice-card 0

dspfarm

dsp services dspfarm

application

service aa flash:app-b-acd-aa-2.1.2.3.tcl

paramspace english index 1

param number-of-hunt-grps 1

param menu-timeout 6

param handoff-string aa

param dial-by-extension-option 5

param max-time-vm-retry 2

param aa-pilot 5555

param max-extension-length 4

paramspace english location flash:

param voice-mail 6000

param service-name queue

service queue flash:app-b-acd-2.1.2.3.tcl

param aa-hunt3 2222

param queue-len 10

param number-of-hunt-grps 1

Re: Wireless DHCP problem

Justin Kurynny — Thu, 15 Mar 2012 06:49:28 GMT

Kamran,

The problem is that your AP is set up for trunking. The client associates, sends a DHCP request, and the AP tags it with 802.1q tag 30 before sending to the switch. The switchport is set up for access and doesn't understand tags, so the packet is dropped.

You need to change your switchport for your AP to look like this:

interface

description AP

switchport trunk encapsulation dot1q

switchport mode trunk

You will need to tag your BVI interface with VLAN 30 and put it in bridge-group 195 if you want to reach its management IP (30.10).

Alternatively, you can strip out all the VLAN tagging and subinterfaces on your AP and just do everything on the default VLAN. In this setup you can leave your switchport as an access port in VLAN 30.

Justin

Re: Wireless DHCP problem

Kamran Mustafayev — Thu, 15 Mar 2012 07:02:42 GMT

Justin,

But on AP interface there is no command to change switchport encapsulation or make trunk,

or you mean Switchport ?

Re: Wireless DHCP problem

Justin Kurynny — Thu, 15 Mar 2012 07:22:23 GMT

Kamran,

Yes, sorry, that was unclear. Make your switchport interface the trunk. You do this on the switch:

(config-if)switch# switchport trunk encap dot1q

(config-if)switch# switchport mode trunk

Justin

Sent from Cisco Technical Support iPhone App

Re: Wireless DHCP problem

Kamran Mustafayev — Thu, 15 Mar 2012 08:13:21 GMT

Yep, it worked, thank you Justin

Also it the first time i see config like

switchport access vlan 30

switchport trunk encapsulation dot1q

switchport mode trunk

Cisco classic wireless scheme when ap is in access mode by default with switchport

thank you

Re: Wireless DHCP problem

Justin Kurynny — Thu, 15 Mar 2012 15:35:57 GMT

Kamran,

When a switchport is in trunking mode, the switchport access vlan command has no effect. You can remove it safely with the no form of that command.

Justin

Re: Wireless DHCP problem

Kamran Mustafayev — Fri, 16 Mar 2012 05:24:58 GMT

Justin, if it has no effect, why when i remove access vlan, wireless ap stops broadcasting dhcp?

Re: Wireless DHCP problem

Justin Kurynny — Fri, 16 Mar 2012 06:08:05 GMT

Kamran,

The switchport access vlan command is only relevant when the switchport is set to switchport mode access. In access mode, the configured VLAN acts like a “native” vlan—all untagged traffic coming into the port is classified on the switch as part of that vlan-id. When you change the switchport mode to trunking (switchpport mode trunk), the access vlan statement is ignored and the port starts using the 802.1q extensions for frame classification. By default, the native vlan is 1 (this is the vlan that untagged traffic coming or going is placed in) and tagged traffic is both accepted incoming and passed outgoing.

At least that’s my understanding. ☺

Because you are using dot1q encapsulation on your AP, the AP is sending frames out with the vlan 30 tag and with your switchport in trunking mode, the traffic flows. Your BVI1 interface is essentially in the default vlan, which is why pings worked when you still had your switchport as an access port set for vlan 30.

Can you copy/paste the configuration for the switchport? Now you have me scratching my head..

Justin