switch 2960 don't pass DHCP

[eyongesi]

Dear All,

I have setup etherchannel trunk between 2 2960 switches, the PC's in 1st switch connected directly to the router receives DHCP addresses that are configured in the router.

The PC's on the 2nd switch forming an etherchannel trunk between the 1st switch don't receive dhcp IP addresses. 

I have even enabled ip-helper on the vlan interfaces but still don't work.

Configuration scenario: R1---->SW1---etherchannel----SW2

PC's behind SW1 DHCP OK, PC's behind SW2 DHCP Not OK.

R1 is router on stick hosting the dhcp server

Please your help will be appreciated.

[Jon Marshall]

What vlan is PC on SW2 in ? 

Can you post from the switch - 

"sh vlan brief"

"sh int trunk" 

and the router configuration. 

Jon

[eyongesi]

SW2 has 2 Vlans: Vlan 30 and Vlan40

show cmd: 

BUREAU#sh vlan brief

VLAN Name Status Ports

---- -------------------------------- --------- -------------------------------

1 default active Fa0/16, Fa0/17, Fa0/18, Fa0/19

Fa0/20, Fa0/21, Fa0/22, Gig0/1

Gig0/2

10 Administration active

20 Control active

30 Bureaux123 active Fa0/1, Fa0/2, Fa0/3, Fa0/4

Fa0/5, Fa0/6, Fa0/7, Fa0/8

Fa0/9

40 Bureaux45 active Fa0/10, Fa0/11, Fa0/12, Fa0/13

Fa0/14, Fa0/15

1002 fddi-default active

1003 token-ring-default active

1004 fddinet-default active

1005 trnet-default active

BUREAU#sh interfaces trunk

Port Mode Encapsulation Status Native vlan

Po1 on 802.1q trunking 1

Port Vlans allowed on trunk

Po1 1-1005

Port Vlans allowed and active in management domain

Po1 1,10,20,30,40

Port Vlans in spanning tree forwarding state and not pruned

Po1 1,10,20,30,40

[Jon Marshall]

And the router configuration ?

Jon

[eyongesi]

Here Below is the R1 Config:

R1#sh run

Building configuration...

Current configuration : 1962 bytes

!

version 15.1

no service timestamps log datetime msec

no service timestamps debug datetime msec

no service password-encryption

!

hostname LAN228

!

!

!

!

ip dhcp excluded-address 192.168.10.1 192.168.10.5

ip dhcp excluded-address 192.168.20.1 192.168.20.5

ip dhcp excluded-address 192.168.30.1 192.168.30.5

ip dhcp excluded-address 192.168.40.1 192.168.40.5

!

ip dhcp pool VLAN10

network 192.168.10.0 255.255.255.0

default-router 192.168.10.1

dns-server 210.5.126.1

ip dhcp pool VLAN20

network 192.168.20.0 255.255.255.0

default-router 192.168.20.1

dns-server 210.5.126.1

ip dhcp pool VLAN30

network 192.168.30.0 255.255.255.0

default-router 192.168.30.1

dns-server 210.5.126.1

ip dhcp pool VLAN40

network 192.168.40.0 255.255.255.0

default-router 192.168.40.1

dns-server 210.5.126.1

!

!

!

no ip cef

no ipv6 cef

!

!

!

!

license udi pid CISCO2901/K9 sn FTX1524D5EW

!

!

!

!

!

!

!

!

!

!

!

spanning-tree mode pvst

!

!

!

!

!

!

interface GigabitEthernet0/0

no ip address

duplex auto

speed auto

shutdown

!

interface GigabitEthernet0/1

no ip address

duplex auto

speed auto

!

interface GigabitEthernet0/1.10

description Administration.Vlan

encapsulation dot1Q 10

ip address 192.168.10.1 255.255.255.0

ip nat inside

!

interface GigabitEthernet0/1.20

description Control.Vlan

encapsulation dot1Q 20

ip address 192.168.20.1 255.255.255.0

ip nat inside

!

interface GigabitEthernet0/1.30

description Bureaux123

encapsulation dot1Q 30

ip address 192.168.30.1 255.255.255.0

ip nat inside

!

interface GigabitEthernet0/1.40

description Bureaux45

encapsulation dot1Q 40

ip address 192.168.40.1 255.255.255.0

ip nat inside

!

interface FastEthernet0/0/0

!

interface FastEthernet0/0/1

!

interface FastEthernet0/0/2

switchport mode access

!

interface FastEthernet0/0/3

switchport mode access

!

interface Vlan1

no ip address

shutdown

!

ip classless

!

ip flow-export version 9

!

!

!

!

!

!

!

line con 0

!

line aux 0

!

line vty 0 4

login

!

!

!

end

And SW1 Connected to R1 Config:

ADMIN#sh run
Building configuration...

Current configuration : 3026 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname ADMIN
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
interface Port-channel1
switchport mode trunk
!
interface FastEthernet0/1
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/2
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/3
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/4
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/5
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/6
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/7
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/8
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/9
description Administration_LAN
switchport access vlan 10
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/10
description Control_LAN
switchport access vlan 20
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/11
description Control_LAN
switchport access vlan 20
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/12
description Control_LAN
switchport access vlan 20
switchport mode access
spanning-tree portfast
!
interface FastEthernet0/13
description Control_LAN
switchport mode access
!
interface FastEthernet0/14
switchport mode access
!
interface FastEthernet0/15
switchport mode access
!
interface FastEthernet0/16
switchport mode access
!
interface FastEthernet0/17
switchport mode access
!
interface FastEthernet0/18
switchport mode access
!
interface FastEthernet0/19
switchport mode access
!
interface FastEthernet0/20
switchport mode access
!
interface FastEthernet0/21
switchport mode access
!
interface FastEthernet0/22
switchport mode access
!
interface FastEthernet0/23
switchport mode trunk
channel-group 1 mode on
!
interface FastEthernet0/24
switchport mode trunk
channel-group 1 mode on
!
interface GigabitEthernet0/1
description TRUNK-ROUTER
switchport mode trunk
!
interface GigabitEthernet0/2
!
interface Vlan1
no ip address
shutdown
!
interface Vlan10
description Administration.LAN
mac-address 00e0.f77e.4202
ip address 192.168.10.2 255.255.255.0
!
interface Vlan20
description Control.LAN
mac-address 00e0.f77e.4201
ip address 192.168.20.2 255.255.255.0
!
!
!
!
line con 0
!
line vty 0 4
login
line vty 5 15
login
!
!
!
end

[Richard Burts]

Which interface on SW1 connects to the router? Can you post the output of show interface trunk from SW1?

HTH

Rick

[eyongesi]

SW1 gig0/1 connects to R1 gig0/1 interface

SW1 output of sh int trunk

SW1#sh interfaces trunk

Port Mode Encapsulation Status Native vlan

Po1 on 802.1q trunking 1

Gig0/1 on 802.1q trunking 1

Port Vlans allowed on trunk

Po1 1-1005

Gig0/1 1-1005

Port Vlans allowed and active in management domain

Po1 1,10,20

Gig0/1 1,10,20

Port Vlans in spanning tree forwarding state and not pruned

Po1 1,10,20

Gig0/1 1,10,20

SW2 output of sh int trunk

SW2#sh interfaces trunk
Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 1

Port Vlans allowed on trunk
Po1 1-1005

Port Vlans allowed and active in management domain
Po1 1,30,40

Port Vlans in spanning tree forwarding state and not pruned
Po1 1,30,40

[Richard Burts]

Thanks for the information. It does clearly show the issue

Port Vlans in spanning tree forwarding state and not pruned

Po1 1,10,20

Gig0/1 1,10,20

It shows that neither vlan 30 or 40 is included on the trunk connecting to the router. I do not see anything in the config of SW1 that would explain this. Can you post the show run from SW2?

HTH

Rick

[eyongesi]

Dear Support, please find the output of sh run on SW2

SW2#sh run

Building configuration...

Current configuration : 2571 bytes

!

version 12.2

no service timestamps log datetime msec

no service timestamps debug datetime msec

no service password-encryption

!

hostname SW2

!

!

!

!

!

spanning-tree mode pvst

spanning-tree extend system-id

!

interface Port-channel1

switchport mode trunk

!

interface FastEthernet0/1

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/2

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/3

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/4

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/5

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/6

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/7

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/8

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/9

switchport access vlan 30

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/10

switchport access vlan 40

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/11

switchport access vlan 40

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/12

switchport access vlan 40

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/13

switchport access vlan 40

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/14

switchport access vlan 40

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/15

switchport access vlan 40

switchport mode access

spanning-tree portfast

!

interface FastEthernet0/16

!

interface FastEthernet0/17

!

interface FastEthernet0/18

!

interface FastEthernet0/19

!

interface FastEthernet0/20

!

interface FastEthernet0/21

!

interface FastEthernet0/22

!

interface FastEthernet0/23

switchport mode trunk

channel-group 1 mode on

!

interface FastEthernet0/24

switchport mode trunk

channel-group 1 mode on

!

interface GigabitEthernet0/1

!

interface GigabitEthernet0/2

!

interface Vlan1

no ip address

shutdown

!

interface Vlan30

description Bureaux123Lan

mac-address 0030.a3a1.9d01

ip address 192.168.30.2 255.255.255.0

!

interface Vlan40

description Bureaux45Lan

mac-address 0030.a3a1.9d02

ip address 192.168.40.2 255.255.255.0

!

!

!

!

line con 0

!

line vty 0 4

login

line vty 5 15

login

!

!

!

end

Bureau#

[Georg Pauwen]

Hello,

delete the Vlan 30 and Vlan 40 interfaces on SW2, these are redundant since you have the layer 3 interfaces configured on your router.

Also, post the output of 'show vtp status' of both switches...

[eyongesi]

Hi Georg,

Vlan 30 and Vlan 40 interfacs has been deleted on SW2 as required.

SW1 vtp Status output

SW1#sh vtp status

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 255

Number of existing VLANs : 7

VTP Operating Mode : Server

VTP Domain Name :

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : 0x0D 0x30 0x8C 0x7A 0xCC 0x46 0xAD 0x4F

Configuration last modified by 0.0.0.0 at 3-1-93 00:12:16

Local updater ID is 192.168.10.2 on interface Vl10 (lowest numbered VLAN interface found)

SW2 vtp Status output

SW2#sh vtp status

VTP Version : 2

Configuration Revision : 4

Maximum VLANs supported locally : 255

Number of existing VLANs : 7

VTP Operating Mode : Server

VTP Domain Name :

VTP Pruning Mode : Disabled

VTP V2 Mode : Disabled

VTP Traps Generation : Disabled

MD5 digest : 0x2E 0xAB 0x59 0x55 0x3D 0x75 0x4E 0xA7

Configuration last modified by 0.0.0.0 at 3-1-93 00:25:28

Local updater ID is 0.0.0.0 (no valid interface found)

[Georg Pauwen · Accepted solution]

Hello,

configure SW1 as VTP server and SW2 as VTP client, configure both for the same VTP domain (you can choose whatever domain name you want):

SW1(config)#vtp mode server

SW1(config)#vtp domain YOURDOMAIN

SW2(config)#vtp mode client

SW2(config)#vtp domain YOURDOMAIN

[eyongesi]

Hi Georg,

Thanks very much for your assistance. It worked like magic.

In summary when a layer 3 device has Vlan configurations, no need to configure vlan interfaces on the switch and if 2 switches are trunking, one has to be a server and the other client.

Thanks So much.