VLT Configuration/Port Channel Issue

Hi All,

I'm wondering if you can help me. We have just purchased some Dell Force 10 S4048 and S3148 switches. I have got the S4048s configured in VLT. The switches see each other and have a Backup link connected which is also available. I have then connected a couple of S3148 switches to them using a VLT Port Channel. Everything is working and connectivity can be established, however, one of the interfaces to each S3148 is currently in a down state. They were both operational for a short while before going down. Below is the configuration for one of the S3148s, to save anyone getting confused.

S4048-1#show run int te1/24
!
interface TenGigabitEthernet 1/24
description ** Link to S3148show -1 **
no ip address
!
port-channel-protocol LACP
port-channel 9 mode active
no shutdown
!
S4048-1#show run in po9
!
interface Port-channel 9
description ** Link to S3148-1 **
no ip address
portmode hybrid
switchport
vlan-stack trunk
vlt-peer-lag port-channel 9
no shutdown
!
S4048-1#show vlt det
Local LAG Id Peer LAG Id Local Status Peer Status Active VLANs
------------ ----------- ------------ ----------- -------------
9 9 UP DOWN 1, 100-101, 104-105, 301,
305, 323, 2564

S4048-2#show run int te1/24
!
interface TenGigabitEthernet 1/24
description ** Link to S3148-1 **
no ip address
!
port-channel-protocol LACP
port-channel 9 mode active
no shutdown
S4048-2#show run int po9
!
interface Port-channel 9
description ** Link to S3148-1 **
no ip address
portmode hybrid
switchport
vlan-stack trunk
vlt-peer-lag port-channel 9
no shutdown
!
S4048-2#show vlt det
Local LAG Id Peer LAG Id Local Status Peer Status Active VLANs
------------ ----------- ------------ ----------- -------------
9 9 DOWN UP 1, 100-101, 104-105, 301,
305, 323, 2564

3148-1#show run int Gi1/48
!
interface GigabitEthernet 1/48
description ** Link to S4048-2 **
no ip address
!
port-channel-protocol LACP
port-channel 9 mode active
no shutdown
3148-1#show run int Gi1/47
!
interface GigabitEthernet 1/47
description ** Link to S4048-1 **
no ip address
!
port-channel-protocol LACP
port-channel 9 mode active
no shutdown
!
S3148-1#show run int po9
!
interface Port-channel 9
description ** Link to S4048s **
no ip address
portmode hybrid
switchport
vlan-stack trunk
no shutdown

If anyone could shed some light as to why the interfaces are doing this it would be appreciated. We are looking to use these in our primary data centre so need to get it working.

Many Thanks,

Talan