HRSP Both Core Switches Active - Vlan Connectivity Issues

[wcoxy]

Hi

We experienced an issue with one of our vlans over the weekend, where some locations/hosts could still communicate over this vlan, but others couldn't.  Eventually we found the HRSP state on our two core switch stacks was showing as active on both and the standby was showing as unknown.

Core 1:

standby 1 timers 1 4
standby 1 priority 200
standby 1 preempt delay minimum 60

Core 2: 

standby 1 timers 1 4
standby 1 priority 150
standby 1 preempt delay minimum 60

We tried swapping the priorities and disabling/re-enabling the vlan to try and force it to reset, but it feels like there is no communication between the core switches to allow it to know which one should be active and which one standby.  

We can ping between the core switches, so there is layer 2 communication.

We've had to leave the vlan disabled on one of the core switches to help, but there are still some locations/hosts that cannot communicate across this vlan.

I have also noticed that this vlan has another access switch set as the spanning tree root port (which is blocked on one of the core switches), whereas the other vlans have the etherchannel port set as the root.  

Core 1: 

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/0/2 Desg FWD 4 128.2 P2p
Gi1/0/3 Desg FWD 4 128.3 P2p
Po1 Altn BLK 3 128.488 P2p
Gi2/0/2 Desg FWD 4 128.56 P2p
Fa2/0/1 Desg FWD 19 128.57 P2p
Fa2/0/2 Desg FWD 19 128.58 P2p
Fa2/0/4 Desg FWD 19 128.60 P2p
Fa2/0/5 Root FWD 19 128.61 P2p
Fa2/0/6 Desg FWD 19 128.62 P2p
Fa2/0/7 Desg FWD 19 128.63 P2p
Fa2/0/9 Desg FWD 19 128.65 P2p
Fa2/0/10 Desg FWD 19 128.66 P2p
Fa2/0/12 Desg FWD 19 128.68 P2p
Fa2/0/13 Desg FWD 19 128.69 P2p

Core 2: 

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Po1 Desg FWD 3 128.488 P2p
Gi2/0/2 Desg FWD 4 128.56 P2p
Fa2/0/1 Desg FWD 19 128.57 P2p
Fa2/0/2 Desg FWD 19 128.58 P2p
Fa2/0/4 Desg FWD 19 128.60 P2p
Fa2/0/5 Root BLK 19 128.61 P2p
Fa2/0/9 Desg FWD 19 128.65 P2p
Fa2/0/11 Desg FWD 19 128.67 P2p
Fa2/0/12 Desg FWD 19 128.68 P2p
Fa2/0/13 Desg FWD 19 128.69 P2p

Unfortunately, I am not a Cisco or networking expert, so any help would be appreciated.

[balaji.bandi · Accepted solution]

BLK means - the STP blocking the port -

This causes some of the Switch port particiapated in the network and have alternative path.

To fix this you need to identify where is alternative path, or need to configurre STP priority  for that VLAN.

#show spanning-tree vlan XX (where this VLAN you mentioned as blocking)

you can also set spanningtree priority

spanning-tree vlan xxx priority 4096 (Primary Core)

spanning-tree vlan xxx priority 8192 (secondary  Core)

[wcoxy]

I can see that the spanning tree priority has been set for some of our vlans, but not the one that has the issue.

spanning-tree vlan 2,4,6,8,86,100,110,112,120,158,176,192 priority 8192
spanning-tree vlan 3,5,7,111,157,193,195,197 priority 4096

We've had no issues with this vlan for over 3 years, so why would an issue suddenly appear and will adding this vlan to the list fix our issue?

[balaji.bandi]

its been running all years good, but when the STP topology changes that might have kicked to STP block mode.

Glad to hear all good and working as expected. STP is evil we need to be more cautious if not setup correctly (it bring down the network).

[wcoxy]

Thank you BB

Your suggestion to set the spanning tree priority resolved our issue.