Cisco 2960s Stack High availability issue

[Mohammed Ashraf Ali]

Hi All,

Recently we have deployed 2 2960s series switches with flexstack module, and configured as:

1) company-sw1#sh switch neighbors

  Switch #    Port 1       Port 2

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

      1            2              2 

      2            1              1

2)company-sw1#  sh switch

Switch/Stack Mac Address : 2401.c7ef.1300

Mac persistency wait time: Indefinite

                                           H/W   Current

Switch#  Role   Mac Address      Priority Version  State

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

*1       Master  2401.c7ef.1300      14         1         Ready              

2       Member 2401.c7e5.7a00     2          1         Ready              

3       Member 0000.0000.0000     0          1         Provisioned

3) company-sw1# sh run

stack-mac persistent timer 0

interface Port-channel1

switchport mode access

!        

interface Port-channel2

switchport mode access

interface GigabitEthernet1/0/1

switchport mode access

spanning-tree portfast

channel-protocol lacp

channel-group 1 mode active

!        

interface GigabitEthernet1/0/2

switchport mode access

spanning-tree portfast

channel-protocol lacp

channel-group 2 mode active

interface GigabitEthernet2/0/1

switchport mode access

spanning-tree portfast

channel-protocol lacp

channel-group 1 mode active

!        

interface GigabitEthernet2/0/2

switchport mode access

spanning-tree portfast

channel-protocol lacp

channel-group 2 mode active

!        

AT the server side , we have configured teeming (bond) of eth0 and eth1 with 802.3ad protocol support for both the servers, teaming is working fine.

And started the ping from one server to other ,

1. And if i poweroff  the Master switch , there is no issue (no dropages in the icmp request/reply or Tcp ).

2. Even though  the Master switch comes back, the  member becomes Master , and stays as it is until the new master restarts.

3. But if i powerof the the new Master which is using the persistent mac of old master switch, i lose the atleast 3 icmp packet.

Pls reply....

Regards,

Ashraf

[Reza Sharifi]

Hi Ashraf,

With Portchannel, you loose what is already in the wire when you tun off the master or member.  If for example the server is using interface 2/0/2, you are not going to see any packet drops, because the packet is traversing the member switch. Now if the server using port 1/0/1, when you shut down the master, you will see a 1, 2 or 3 packet drops and that is what is in the wire.

If you want to know what port the switch is using to forward packet at any time use this command:

test etherchannel load-balance interface port-channel xx mac .......

HTH

[Mohammed Ashraf Ali]

Many Thanks Reza,

i hve few quick questions.

1. Can we improve this process of portchannel with some configuration , so that i will not loose those 1,2 or 3 packet drops, is it possible....

2. Will there be any difference if i connect the Stack in Cisco 2960s , as port1 of switch1 to port 1 of switch2 and  port2 of switch1 to port2 of switch2  OR  port1 of switch1 to port2 of switch2 and port2 of switch1 to port1 of switch2.

Regards,

Ashraf