2960 Stack switch, no loss if one uplink connected from master switch.If both uplinks are connected, huge packet loss...

[preetpeethambaran]

2 uplinks are going from 2960 4 member stack to 4503 Active and Standby HSRP Core Swtich.If only one uplink is connected everything working fine.If both uplinks are connected to core, Huge packet drop is experienced, even file copying getting breaked in between. 

[Naren K]

You will need to provide more information like logs, diagram with port detail, existing spanning configuration etc. Also the issue is with all traffic on access switch or is with any particular VLAN. The packet drops are continues or intermittent then what is time ratio?

There could be many reasons like layer 2 loop, STP, port fluctuation, collusion, or cable or interface issue, even can’t eliminate any of host system is virus infected.

Happy to help

[preetpeethambaran]

Please find the network diagram. In 2960 Stack Switch, when Gi 1/0/50 uplink is removed, everything is working fine.When both Gi 1/0/49 & Gi 1/0/50 both are connect, huge packet drop is happening.I reconfigured the entire Stack and everything worked fine with 2 uplinks for 2 days, but now the same issue is facing with huge packet loss.

[preetpeethambaran]

This Packet loss is happening with all hosts connected to the entire stack switch...

[Leo Laohoo]

2 uplinks are going from 2960 4 member stack to 4503 Active and Standby HSRP Core Swtich

1.  Plain 2960/2960G or 2960S/X/XR?  Which is which?  

2.  What IOS are you switch/switch stack running? 

3.  Did you enable Etherchannel?  If not , why not?

[preetpeethambaran]

Please find the details below.

1. Switch: C2960X

2. Ios: UNIVERSALK9-M,  Version:15.0(2)EX5

3. AS both up links are going to different Core Switch, Configuring ether channel will not provide the desired output....

[Leo Laohoo]

Are the uplinks configured as a 802.1q Trunk ports or plain access ports?

Post the uplink port configurations (both the 2960X and the 4500).

[preetpeethambaran]

Please find the details...

Stack Switch Configuration:

2960X:

interface GigabitEthernet1/0/49----( Active Core)
 switchport mode trunk

interface GigabitEthernet1/0/49----(Standby Core)
 switchport mode trunk

Stack-Switch#sh interfaces trunk 

Port           Mode             Encapsulation  Status        Native vlan
Gi1/0/49       on                  802.1q         trunking      1

Gi1/0/50       on                  802.1q         trunking      1

4503: Core Switch
interface GigabitEthernet3/10
 description *****2nd floor SW2*****
 switchport mode trunk