Problem with DHCP server on 1841 router.

radiomean · ‎08-17-2020

Hi, this is a simple issue but I have been looking at documentation and I can't get anywhere so I will ask the experts...

I am setting up a DHCP server on an 1841 router with a HWIC-AP-AG card. It's running IOS 15.1(3)T2 adventerprise with 256 Mb of ram.

((I know it's all old tech but I have my reasons!))

I am simply using the HWIC-AP card as an access point. I have manually assigned an IP address of 192.168.2.1 to the g wireless and 192.168.5.1 to the a wireless.

I've configured the following DHCP pool:

no ip dhcp conflict logging
ip dhcp excluded-address 192.168.2.1 192.168.2.32
!
ip dhcp pool two
network 192.168.2.0 255.255.255.0
default-router 192.168.2.1
dns-server 8.8.8.8 8.8.4.4
domain-name ****.com
lease 0 2
!

I can associate a laptop fine and access the router using static IP but when I try to use DHCP an address is briefly assigned, then declined and a self-determined IP appears on the laptop. And the next IP address is then assigned and so on...

The output of the DHCP server is below: (I have snipped it because my last post was marked as spam...)

Advice is greatly received as to what I am doing wrong please?

Cheers, Bill

secureitgroup · ‎08-17-2020

Hello,

I have one additional question.... Can you elaborate on this portion of your post
"to the g wireless and 192.168.5.1 to the a wireless."

The snip did not come through either so if you can re-attach that would be very helpful, in the even you have wireshark on the pc you can follow the DORA Process and see were you get.

radiomean · ‎08-17-2020

Hi, and thanks...

The HWIC AP card incorporates two radios - g (2.4 GHz) and a (5 GHz). I have manually assigned an IP of 192.168.2.1 to the g radio and and IP of 192.168.5.1 to the a radio.

Here is the output of 'debug ip dhcp server events'

*Aug 17 23:29:20.443: %DOT11-6-ASSOC: Interface Dot11Radio0/1/0, Station 5426.96dc.fad1 Associated SSID[ciscotest2] AUTH_TYPE[OPEN] KEY_MGMT[NONE]
*Aug 17 23:29:20.451: DHCPD: Sending notification of DISCOVER:
*Aug 17 23:29:20.455: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:20.455: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:20.455: DHCPD: circuit id 00000000
*Aug 17 23:29:20.455: DHCPD: Seeing if there is an internally specified pool class:
*Aug 17 23:29:20.455: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:20.455: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:20.455: DHCPD: circuit id 00000000
*Aug 17 23:29:20.455: DHCPD: Found previous server binding
*Aug 17 23:29:21.459: DHCPD: Sending notification of ASSIGNMENT:
*Aug 17 23:29:21.459: DHCPD: address 192.168.2.44 mask 255.255.255.0
*Aug 17 23:29:21.459: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:21.459: DHCPD: lease time remaining (secs) = 7200
*Aug 17 23:29:22.983: DHCPD: Sending notification of TERMINATION:
*Aug 17 23:29:22.983: DHCPD: address 192.168.2.44 mask 255.255.255.0
*Aug 17 23:29:22.983: DHCPD: reason flags: DECLINE
*Aug 17 23:29:22.983: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:22.983: DHCPD: lease time remaining (secs) = 7199
*Aug 17 23:29:22.983: DHCPD: returned 192.168.2.44 to address pool two.
*Aug 17 23:29:32.995: DHCPD: Sending notification of DISCOVER:
*Aug 17 23:29:32.995: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:32.995: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:32.995: DHCPD: circuit id 00000000
*Aug 17 23:29:32.995: DHCPD: Seeing if there is an internally specified pool class:
*Aug 17 23:29:32.995: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:32.995: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:32.995: DHCPD: circuit id 00000000
*Aug 17 23:29:32.995: DHCPD: Adding binding to radix tree (192.168.2.45)
*Aug 17 23:29:32.995: DHCPD: Adding binding to hash tree
*Aug 17 23:29:32.995: DHCPD: assigned IP address 192.168.2.45 to client 0154.2696.dcfa.d1.
*Aug 17 23:29:34.671: DHCPD: Sending notification of DISCOVER:
*Aug 17 23:29:34.671: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:34.671: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:34.671: DHCPD: circuit id 00000000
*Aug 17 23:29:34.671: DHCPD: Seeing if there is an internally specified pool class:
*Aug 17 23:29:34.675: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:34.675: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:34.675: DHCPD: circuit id 00000000
*Aug 17 23:29:34.675: DHCPD: Found previous server binding
*Aug 17 23:29:34.995: DHCPD: Sending notification of DISCOVER:
*Aug 17 23:29:34.995: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:34.995: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:34.995: DHCPD: circuit id 00000000
*Aug 17 23:29:34.995: DHCPD: Seeing if there is an internally specified pool class:
*Aug 17 23:29:34.995: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:34.995: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:34.995: DHCPD: circuit id 00000000
*Aug 17 23:29:34.995: DHCPD: Found previous server binding
*Aug 17 23:29:36.039: DHCPD: Sending notification of ASSIGNMENT:
*Aug 17 23:29:36.039: DHCPD: address 192.168.2.45 mask 255.255.255.0
*Aug 17 23:29:36.039: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:36.039: DHCPD: lease time remaining (secs) = 7200
*Aug 17 23:29:37.667: DHCPD: Sending notification of TERMINATION:
*Aug 17 23:29:37.667: DHCPD: address 192.168.2.45 mask 255.255.255.0
*Aug 17 23:29:37.667: DHCPD: reason flags: DECLINE
*Aug 17 23:29:37.667: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:37.667: DHCPD: lease time remaining (secs) = 7199
*Aug 17 23:29:37.667: DHCPD: returned 192.168.2.45 to address pool two.
*Aug 17 23:29:47.675: DHCPD: Sending notification of DISCOVER:
*Aug 17 23:29:47.675: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:47.675: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:47.675: DHCPD: circuit id 00000000
*Aug 17 23:29:47.675: DHCPD: Seeing if there is an internally specified pool class:
*Aug 17 23:29:47.675: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:47.675: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:47.675: DHCPD: circuit id 00000000
*Aug 17 23:29:47.675: DHCPD: Adding binding to radix tree (192.168.2.46)
*Aug 17 23:29:47.679: DHCPD: Adding binding to hash tree
*Aug 17 23:29:47.679: DHCPD: assigned IP address 192.168.2.46 to client 0154.2696.dcfa.d1.
*Aug 17 23:29:48.947: DHCPD: Sending notification of DISCOVER:
*Aug 17 23:29:48.947: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:48.947: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:48.951: DHCPD: circuit id 00000000
*Aug 17 23:29:48.951: DHCPD: Seeing if there is an internally specified pool class:
*Aug 17 23:29:48.951: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:48.951: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:48.951: DHCPD: circuit id 00000000
*Aug 17 23:29:48.951: DHCPD: Found previous server binding
*Aug 17 23:29:49.675: DHCPD: Sending notification of DISCOVER:
*Aug 17 23:29:49.675: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:49.675: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:49.675: DHCPD: circuit id 00000000
*Aug 17 23:29:49.675: DHCPD: Seeing if there is an internally specified pool class:
*Aug 17 23:29:49.675: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:49.675: DHCPD: remote id 020a0000c0a8020101000000
*Aug 17 23:29:49.675: DHCPD: circuit id 00000000
*Aug 17 23:29:49.675: DHCPD: Found previous server binding
*Aug 17 23:29:50.791: DHCPD: Sending notification of ASSIGNMENT:
*Aug 17 23:29:50.791: DHCPD: address 192.168.2.46 mask 255.255.255.0
*Aug 17 23:29:50.791: DHCPD: htype 1 chaddr 5426.96dc.fad1
*Aug 17 23:29:50.791: DHCPD: lease time remaining (secs) = 7200
*Aug 17 23:29:52.315: DHCPD: Sending notification of TERMINATION:
*Aug 17 23:29:52.315: DHCPD: address 192.168.2.46 mask 255.255.255.0

The laptop is requesting a dhcp IP address, is issued with one but declines it and then increments the IP address by one and tries again.

Cheers!

radiomean · ‎08-17-2020

Hi, here is most of the config...

dot11 ssid ciscotest2
authentication open
guest-mode
!
dot11 ssid ciscotest5
authentication open
guest-mode
!
no ip source-route
!
!
no ip dhcp conflict logging
ip dhcp excluded-address 192.168.2.1 192.168.2.32
!
ip dhcp pool two
network 192.168.2.0 255.255.255.0
default-router 192.168.2.1
dns-server 8.8.8.8 8.8.4.4
domain-name ******.com
lease 0 2
!
!
ip cef
no ip domain lookup
no ipv6 cef
!
multilink bundle-name authenticated
!
crypto pki token default removal timeout 0
license udi pid CISCO1841 sn FCZ1136134U
!
redundancy
!
!
interface FastEthernet0/0
ip address 192.168.0.1 255.255.255.0
duplex auto
speed auto
no mop enabled
!
interface FastEthernet0/1
ip address 192.168.1.1 255.255.255.0
duplex auto
speed auto
no mop enabled
!
interface Dot11Radio0/1/0
ip address 192.168.2.1 255.255.255.0
!
ssid ciscotest2
!
speed basic-1.0 basic-2.0 basic-5.5 6.0 9.0 basic-11.0 12.0 18.0 24.0 36.0 48.0 54.0
station-role root
!
interface Dot11Radio0/1/1
ip address 192.168.5.1 255.255.255.0
!
ssid ciscotest5
!
speed basic-6.0 9.0 basic-12.0 18.0 basic-24.0 36.0 48.0 54.0
station-role root
!
ip forward-protocol nd
ip http server
no ip http secure-server
!
!

Cheers again!

Georg Pauwen · ‎08-17-2020

Hello,

how did you configure the HWIC, can you post that part of the configuration ?

Check if the document below can help.

https://www.cisco.com/c/en/us/td/docs/routers/access/1800/wireless/configuration/guide/awg.html

radiomean · ‎08-17-2020

I've posted most of the config - but it's gone in above your post, confusingly!

I wonder if it's an issue with the IOS version I am using? Surely not, as DCHP will be used very often?

Thanks for the link but I do have that document.

I don't think it is a wireless issue, I think it is something weird with the DHCP server... but I could be wrong!

Cheers, Bill

radiomean · ‎08-17-2020

The board does not seem to want to accept the debug output from debug ip dhcp events.....

I will try again...

===================================

DOT11-6-ASSOC: Interface Dot11Radio0/1/0, Station 5426.96dc.fad1 Associated SSID[ciscotest2] AUTH_TYPE[OPEN] KEY_MGMT[NONE]
DHCPD: Sending notification of DISCOVER:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
: DHCPD: Seeing if there is an internally specified pool class:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
DHCPD: Adding binding to radix tree (192.168.2.61)
DHCPD: Adding binding to hash tree
DHCPD: assigned IP address 192.168.2.61 to client 0154.2696.dcfa.d1.
DHCPD: Sending notification of DISCOVER:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
DHCPD: Seeing if there is an internally specified pool class:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
DHCPD: Found previous server binding
DHCPD: Sending notification of DISCOVER:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
: DHCPD: Seeing if there is an internally specified pool class:
: DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
: DHCPD: Sending notification of ASSIGNMENT:
DHCPD: address 192.168.2.61 mask 255.255.255.0
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: lease time remaining (secs) = 7200
DHCPD: Sending notification of TERMINATION:
: DHCPD: address 192.168.2.61 mask 255.255.255.0
: DHCPD: reason flags: DECLINE
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: lease time remaining (secs) = 7198
: DHCPD: returned 192.168.2.61 to address pool two.
: DHCPD: Sending notification of DISCOVER:
: DHCPD: htype 1 chaddr 5426.96dc.fad1
: DHCPD: remote id 020a0000c0a8020101000000
: DHCPD: circuit id 00000000
DHCPD: Seeing if there is an internally specified pool class:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
: DHCPD: Adding binding to radix tree (192.168.2.62)
DHCPD: Adding binding to hash tree
DHCPD: assigned IP address 192.168.2.62 to client 0154.2696.dcfa.d1.
: DHCPD: Sending notification of DISCOVER:
: DHCPD: htype 1 chaddr 5426.96dc.fad1
: DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
DHCPD: Seeing if there is an internally specified pool class:
DHCPD: htype 1 chaddr 5426.96dc.fad1
: DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
: DHCPD: Found previous server binding
DHCPD: Sending notification of DISCOVER:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
: DHCPD: circuit id 00000000
: DHCPD: Seeing if there is an internally specified pool class:
DHCPD: htype 1 chaddr 5426.96dc.fad1
DHCPD: remote id 020a0000c0a8020101000000
DHCPD: circuit id 00000000
DHCPD: Found previous server binding

The ip address is issued but then declined and the server then increments the address by one and tried again!

Cheers...

radiomean · ‎08-18-2020

Well, I thought I had found the problem but I have not...

I have tried a different image - c1841-advipservicesk9-mz.151-3.T2 and my Android phone got leases fine on 2 and 5 Ghz.

But nothing else does - a Macbook fails, a Surface book fails and an iPad mini fails...

Any further thoughts please?

Cheers...

Georg Pauwen · ‎08-18-2020

Hello,

can you, for the sake of testing, configure a static binding for one of your clients like below ?

ip dhcp pool APPLE
host 192.168.2.31 255.255.255.0
client-identifier 0154.2696.dcfa.d1
default-router 192.168.2.1
dns-server 8.8.8.8 8.8.4.4

radiomean · ‎08-18-2020

That's a great idea!

I also thought of trying DHCP on the wired FE interfaces to see if the issue was with the wireless card...

I'll try and do that tomorrow...

Cheers!

radiomean · ‎08-18-2020

OK, I have tried your suggestion and also tried setting up a DCHP server on one of the FE interfaces - FE1

a) I setup DHCP on FE1 and connected both my Macbook and Surface book sucessfully over ethernet. So it looks like it is not the DHCP server...

b) I tried binding IP to mac address as you suggested (static DHCP) but that failed in exactly the same way as ordinary DHCP.

c) SO - my conclusion so far - is that it's something to do with the Wireless AP card... Maybe it is a Cisco 'feature'? Or just a bug... I can also try IOS 12 but I will have to do that tomorrow.

Cheers again...

radiomean · ‎08-18-2020

Another thought that I have had is that maybe an open AP does not work and I need to configure WPA?

Maybe I will try that tomorrow...

radiomean · ‎08-19-2020

OK, I have now configured WPA2...

Same problem with DHCP...

I have also tried turning off Guestmode on the AP but that does not change anything either.

Apart from now trying a Version 12 image, I'm stumped!

It still goes round and round with the DHCP Offer and DHCP Decline, and incrementing the IP address and trying again...

Any more thoughts please?

radiomean · ‎08-19-2020

I have now tried - c1841-adventerprisek9-mz.124-24.T6 - and all works fine...

DHCP is allocated on both the 2GHz and 5GHz radios...

However, I also need to run a HWIC-3G-HSPA card (not yet arrived) and I have a nasty suspicvion that I need Version 15 to do that!

Oh well...

radiomean · ‎08-19-2020

I seem to have accidentally generated two threads on this, but I have loaded 15.1 (1) T and all works ok, so that's the solution...

But a bit odd that something as fundamental as DHCP is buggy...