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Community Member

STP root change with ACE bridge mode

Hello    

I use ACE in bridge-mode with mac-sticky enabled. Because of the redesign in the network topology I need to change the placement of the stp roots for client and server vlans with the minimal traffic disruption.

I tested such topology in the lab and it seems that the change of the root  for ACE's client vlan causes only 2 seconds disruption but if I change the root for the server vlan the traffic stops to pass through the ace until I clear the ACE's connections.

Does anybody can tell me if this normal behaviour for the ACE bridge-mode and STP change or do I need to implement any modifications, so the migration can be less impacting the bussiness traffic.

Thank you in advance for any help

Regards

Lucas

4 REPLIES

STP root change with ACE bridge mode

Hello Lucas,

Here you have some information:

Configuring a Delay at the Physical Port Level

If you connect an ACE to a Catalyst 6500 series switch, your  configuration on the Catalyst may include the Spanning Tree Protocol  (STP). However, the ACE does not support STP. In this case, you may find  that the Layer 2 convergence time is much longer than the physical port  up time. For example, the physical port would normally be up within 3  seconds, but STP moving to the forward state may need approximately 30  seconds. During this transitional time, although the ACE declares the  port to be up, the traffic will not pass.

To add a configurable delay at the physical port level to address this transition time, based on the variety of peers, use the carrier-delay command.

The syntax for this command is as follows:

carrier-delay seconds

The seconds argument specifies the carrier  transition delay in seconds. Valid values are 0 to 120 seconds. The  default is 0 (no carrier delay).

For example, to add a configurable delay of 60 seconds at the physical port level for Ethernet port 3, enter:

host1/Admin(config)# interface gigabitEthernet 1/3

host1/Admin(config-if)# carrier-delay 60 

To remove the carrier delay for the Ethernet port, enter:

Hope this helps!!!

Community Member

STP root change with ACE bridge mode

Hello

Thank you for your answer but this is not exactly what I need.

I do need to change the STP root for all the ACE vlans from the switch in which the ACE is being placed, to the new AGG switch.

All the ports are up and running. I only need to change the STP priority so the new switch becomes a root for client and server vlan.

As I mentioned earlier, the change in the client vlan, do not impact the traffic in more than 2 seconds, but when I do the same change on the server vlan, I lose the connectivity until I clear the active sessions on the ACE

I am wondering if the "mac-sticky" do not cause these problems.

Regards

Lucas

Community Member

STP root change with ACE bridge mode

Are you running the old PVST+ instead of rapid-PVST+ in your bridged domain?

You can see what the STP is up to at any given moment via show spanning-tree commands:

R3# show spanning-tree vlan 308 interface te7/1 detail
Port 769 (TenGigabitEthernet7/1) of VLAN0308 is designated forwarding
   Port path cost 2, Port priority 128, Port Identifier 128.769.
   Designated root has priority 32768, address 0016.9cec.d474
   Designated bridge has priority 32768, address 001e.791f.5934
   Designated port id is 128.769, designated path cost 4
   Timers: message age 0, forward delay 0, hold 0
   Number of transitions to forwarding state: 1
   The port is in the portfast mode by portfast trunk configuration
   Link type is point-to-point by default
   BPDU: sent 3886427, received 0

S3# show spanning-tree vlan 309 interface te7/1 detail
Port 769 (TenGigabitEthernet7/1) of VLAN0309 is root forwarding
   Port path cost 2, Port priority 128, Port Identifier 128.769.
   Designated root has priority 32768, address 0016.9cec.d474
   Designated bridge has priority 32768, address 001e.791f.5934
   Designated port id is 128.769, designated path cost 4
   Timers: message age 2, forward delay 0, hold 0
   Number of transitions to forwarding state: 1
   Link type is point-to-point by default
   BPDU: sent 3886489, received 3886426

The interface number is #mod/1 , where #mod is the slot number where the ACE is seated.

Use the client/server side Vlans with the command.

Above you see two ports in forwarding state.  If you ever see  a port in listening/learning state, then

you know that the old STP is causing you a 30s delay.

Patrick

Community Member

STP root change with ACE bridge mode

Hi

I use only RSTP.

Regards

Lucas

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