2951 DHCP Problem

Patrick McHenry · ‎10-24-2012

Hi,

I have a small branch office using a 2951 router. I'm using the 2951 as the DHCP server for the site. It is handing out the addresses but, the users tell me in the morning when the come in they have to unplug their cat 5 cable from the wall - then, plug it back in to log in. If they don't do this they can't log in. I'm assuming it is because they aren't getting an address until the unplug and plug in the cat 5 cable.

Has anyone heard of this issue?

Config and show:

ip dhcp excluded-address 172.18.0.58 172.18.0.62

ip dhcp pool corp-pool

import all

network 172.18.0.32 255.255.255.224

domain-name DOMAIN.com

option 150 ip 10.20.64.42 10.20.64.40 10.3.4.40

dns-server 10.3.1.100 10.3.1.108 8.8.8.8

default-router 172.18.0.33

option 43 hex ac14.085d

!

2951#show ip dhcp binding

Bindings from all pools not associated with VRF:

IP address Client-ID/ Lease expiration Type

Hardware address/

User name

172.18.0.34 0100.04f2.ebe1.16 Oct 24 2012 11:34 PM Automatic

172.18.0.36 0100.1cc0.e35e.26 Oct 24 2012 09:02 PM Automatic

172.18.0.37 01c8.0aa9.c112.97 Oct 24 2012 08:48 PM Automatic

172.18.0.39 01c8.0aa9.9efe.62 Oct 25 2012 04:27 AM Automatic

172.18.0.42 0100.0830.8bd2.da Oct 25 2012 12:05 AM Automatic

172.18.0.43 01c8.0aa9.9f06.72 Oct 24 2012 10:24 AM Automatic

172.18.0.45 0168.bc0c.80b4.c0 Oct 25 2012 12:03 AM Automatic

172.18.0.46 0168.bc0c.80b7.3a Oct 25 2012 12:03 AM Automatic

172.18.0.48 0168.bc0c.80bc.f5 Oct 24 2012 09:03 PM Automatic

172.18.0.50 0168.bc0c.80b3.12 Oct 25 2012 12:04 AM Automatic

172.18.0.52 01d8.67d9.e109.44 Oct 24 2012 08:48 PM Automatic

172.18.0.53 01a4.934c.f31f.2e Oct 24 2012 08:55 PM Automatic

172.18.0.56 0160.eb69.c044.2b Oct 25 2012 07:23 AM Automatic

Thanks, Pat.

cadet alain · ‎10-24-2012

Hi,

are the ports connected to clients configured with Portfast ? if not then do it.

Regards.

Alain

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Patrick McHenry · ‎10-24-2012

Yes they are. I should add that these PCs are plugged into a Cisco 7965 IP phone - then, the phone is plugged into the wall.

Switchport config:

interface FastEthernet0/5

description Yolanda G's Office

switchport access vlan 10

switchport mode access

switchport voice vlan 30

spanning-tree portfast

!

Thanks, Pat.

Reza Sharifi · ‎10-24-2012

Pat,

Can you add a lease command to the DHCP pool and test again? If you have no lease, the default is one day. So, try a longer lease time (3 days, 4 days etc...)

HTH

Patrick McHenry · ‎10-24-2012

Reza,

Why do you think that would help?

Thanks, Pat.

Patrick McHenry · ‎10-24-2012

Reza

Are you saying that because the lease is only 1 day - they are forced to get an address every time they log in and the time it takes the PC to get the address is keeping it from logging in?

Thanks, Pat.

Reza Sharifi · ‎10-24-2012

Pat,

That is what I was thinking. I would try a longer lease then one day.

kcnajaf · ‎10-24-2012

Hi Patrick,

Are these DHCP clients windows machines?

If you have a larger dhcp scope and less number of clients try setting the dhcp lease period on the dhcp scope as below.

ip dhcp pool corp-pool

import all

network 172.18.0.32 255.255.255.224

domain-name DOMAIN.com

option 150 ip 10.20.64.42 10.20.64.40 10.3.4.40

dns-server 10.3.1.100 10.3.1.108 8.8.8.8

default-router 172.18.0.33

lease infinite

By default I think the dhcp lease is 1 day and by setting the lease to infinite the clients will not look for the new ip address each day.

Hope this helps.

Regards

Najaf

Patrick McHenry · ‎10-24-2012

Yes they are Windows machines.

There are about 15 clients total and the scope of available addresses. It's is a /27 with 6 of them excluded - so, a total of 25 addresses available.

Will this somehow tie the address to only the mac it first associated with?

So, if an address is allocated to a machine , it will never be allocated to another unless I clear the bindings?

Thanks, Pat.

kcnajaf · ‎10-24-2012

Yes Pat...You are right. When address is allocated to a machine then that ip address would be used by that machine untill you clear the binding..

May be you can try one month lease rather than infinite :-)

Regards

Najaf

Patrick McHenry · ‎10-26-2012

Najaf,

I changed the lease time to 15 days but, still, the users have to unplug there ethernet cables and plug them back in to be able to login

Any more ideas...

Thanks, Pat.

kcnajaf · ‎10-27-2012

Hi Pat,

Could you get the output of ipconfig/all from one of the affected pc?

Also you have mentioned that pc is connected to a phone? Does the phone use dhcp?

Also please do provide full configuration of the switch...,

Regards
Najaf

Sent from Cisco Technical Support iPhone App

Patrick McHenry · ‎10-29-2012

Najaf,

The PCs are connected to the phone and the phones are connected to the network jack. The phones are also dhcp.

Here is the DHCP config on the router portion of the 2951:

ip dhcp pool corp-pool

import all

network 172.18.0.32 255.255.255.224

domain-name Company.com

option 150 ip 10.20.64.42 10.20.64.40 10.3.4.40

dns-server 10.3.1.100 10.3.1.108 8.8.8.8

default-router 172.18.0.33

option 43 hex ac14.085d

lease 15

!

Here is the switch config:

spanning-tree mode pvst
spanning-tree etherchannel guard misconfig
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
!
!
interface FastEthernet0/2
description Con. RM Con Phone
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/3
description Rene V's Office
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/4
description Brian F's Office
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/5
description Yolanda G's Office
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/6
description Cube 1042
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/7
description AP DAL-3502I-2
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/8
description Glen V's Office
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/9
description Ricoh Printer
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/10
description AP DAL-3502I-1
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/11
description Cube 1046
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/12
description Cube 1022
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/13
description Cube 1047
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/14
description Cube 1044
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface FastEthernet0/15
description Cube 1045
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/16
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/17
description Cube 1021
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/18
description Cube 1023
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/19
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/20
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/21
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/22
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/23
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface FastEthernet0/24
switchport access vlan 10
switchport mode access
switchport voice vlan 30
shutdown
spanning-tree portfast
!
interface GigabitEthernet0/1
description HP Scanner
switchport access vlan 10
switchport mode access
switchport voice vlan 30
spanning-tree portfast
!
interface GigabitEthernet0/25
description Trunk to Router
switchport mode trunk
!
interface GigabitEthernet0/26
description Module Port
!
interface Vlan1
no ip address
no ip route-cache
!
interface Vlan10
ip address 172.18.0.62 255.255.255.224
no ip route-cache
!
ip http server
ip http secure-server
ip sla enable reaction-alerts
logging 172.20.8.211
access-list 60 permit 172.20.8.211
access-list 60 deny any log
snmp-server community XXXXXX RO
snmp-server location HQ
!
line con 0
speed 115200
flowcontrol software
line vty 0 4
login local
transport input telnet ssh
line vty 5 15
login local
transport input telnet ssh
!
end

DallasSwitch#

cadet alain · ‎10-29-2012

Hi,

can you explain why you only have one DHCP pool but you are using a separate vlan for the phones ?

Regards.

Alain

Don't forget to rate helpful posts.

Patrick McHenry · ‎10-29-2012

Thanks, Alain -

We are using a separate vlan for the phones only for traffic marking QOS. The phone and the PCs are using the same subnet but, different VLANs. we have several sites using this same design with no problems.

Thanks, Pat.