IBM server connected to 4948 - gives error

[bsn1980in]

Hi

Products

IBM Server with Ethernet Server Connectivity Module, 6 GB Ethernet ports - Qty 1

Cisco 6509 - Oty 02

Cisco 4948 - Qty 02

Earlier setup:  IBM server was connected to 6509-1 and 6509-2 and both switches were connected over a trunk link.  Everything worked fine without any error.

New setup: 4948-1 connected to both 6509 and 4948-2 is also connected to 6509-2.  This gives an error

%C4K_EBM-4-HOSTFLAPPING: Host 00:21:5E:30:0B:0A in vlan 112 is flapping between port Te1/49 and port Gi1/44

                                   

In old setup, server MAC is only learned through 6509-1 port.  No spanning-tree blocked ports were on either of switch.

However in new setup, ports from both 4948 towards 6509-2 are in blocked state.

It is clearly a layer 2 loop.  How can I avoid it? And why it is not occuring when directly conneting server to both 6509 switches.

rgds/bsn

[Jon Marshall]

bsn1980in wrote:
Hi
Products
IBM Server with Ethernet Server Connectivity Module, 6 GB Ethernet ports - Qty 1
Cisco 6509 - Oty 02
Cisco 4948 - Qty 02
Earlier setup:  IBM server was connected to 6509-1 and 6509-2 and both switches were connected over a trunk link.  Everything worked fine without any error.
New setup: 4948-1 connected to both 6509 and 4948-2 is also connected to 6509-2.  This gives an error
%C4K_EBM-4-HOSTFLAPPING: Host 00:21:5E:30:0B:0A in vlan 112 is flapping between port Te1/49 and port Gi1/44
                                    
In old setup, server MAC is only learned through 6509-1 port.  No spanning-tree blocked ports were on either of switch.
However in new setup, ports from both 4948 towards 6509-2 are in blocked state. 
It is clearly a layer 2 loop.  How can I avoid it? And why it is not occuring when directly conneting server to both 6509 switches.
rgds/bsn

What is port gi1/44 ie. it is not in your diagram.

Jon

[bsn1980in]

Please find below:

[bsn1980in]

Sorry.

There is change in diagram.  Server is connected to Gig1/44 instead of Gig8/45.

rgds/bsn

[Jon Marshall]

Are both the NICs on the server active or is one active and one standby ?

How are the NICs configured in terms of IP addressing ?

Jon

[bsn1980in]

Server NIC are connected to balde swithces.  The blade switches are connected to 4948 switches.

Server IP is configured as Virtual IP.

[Jon Marshall]

Can you post diagram again showing blade switches and which links are blocking and which are forwarding.

Jon

[bsn1980in]

[bsn1980in]

Couldn't insert picutre.  Hence sending as an attachment.

[Jon Marshall]

Sorry to be a pain but your diagram shows the blade switch forwarding on both ports but if it is then you have a L2 loop in your network. One of the blade server uplinks should be blocking.

I'm assuming the server is in vlan 112 and your diagram is showing the links blocking for vlan 112 ?

Jon

[Jon Marshall]

Follow up to previous post.

Is the blade interconnect blocking ? ie. in which case you don't have a loop.

Jon

[bsn1980in]

No there is no blocking in old case.  When I saw ARP entries, Server MAC can only be learnt on 6509-1.  And on 6509-2, it was learnt through 6509-1. Only one way learning of MAC, hence no loop / error.

rgds/bsn

[Jon Marshall]

bsn1980in wrote:
No there is no blocking in old case.  When I saw ARP entries, Server MAC can only be learnt on 6509-1.  And on 6509-2, it was learnt through 6509-1. Only one way learning of MAC, hence no loop / error.
rgds/bsn

So on the blade chassis you have servers and you have a switch at either end of the chassis ?

There is also internally a switch interconnect between the 2 blade switches. Now i'm guessing this must have been blocked because if it wasn't even in the old case you would have a loop.

On each of the switches can you do a "sh spanning-tree vlan 112" and post.

Also the NICs, they share a virtual IP but do they function in active/standby mode ie. only NIC is forwarding at any one time ?

Jon