Wired Intelligent Edge (Campus Switching and Routing)

Contributor II

Re: Converting SFPs from stacking to uplink in 2500

 It is strange that disabling STP brings down the link. STP doesn't control physical link/port properties.


Now, With ports connected on S1500 with Corinex, and STP enabled (spanning-tree mode mstp),

Can you dump the o/p of  "show interface gigabitethernet <x/y/z>" for ports on both S1500s ?


And, when you say  "When I connect them to any 2 switches they work fine"

 - which switches are you refering to ?


Also, to confirm the connectivity, is this how they are connected ?


S1500-ONE {GE-0/0/1} --------- [Corinex adapter]------------ {GE-0/0/1} S1500-TWO





Contributor I

Re: Converting SFPs from stacking to uplink in 2500

The link was done due to another issue
But when I convert it to PVST, everthing worked

But do we have a way to keep the MSTP and unblock the traffic



Contributor II

Re: Converting SFPs from stacking to uplink in 2500


As we know PVST runs seperate STP instances per VLAN, whch makes some ports in "Forward" state in some VLANs & blocking in others, hence we can achieve kind of load-balancing of traffic


 Similar thing can be achieved in MSTP as-well.

 By default when you enable MSTP, only one 'instance' is running which spans on VLANS on the system.

  For better load-balancing of traffic, you can create multiple MST "instances": via something called as "instance VLAN mapping"

  This needs bit planning & deciding a root-bridge for each of those instances for "optimal" topology.

Sample config like below needs to  be configured on all the switches in your topology


(IDF-1) (config) #mstp

(IDF-1) (Global MSTP) #region-name REG-1

(IDF-1) (Global MSTP) #instance 0 bridge-priority 16384

(IDF-1) (Global MSTP) #instance 1 bridge-priority 32768

(IDF-1) (Global MSTP) #instance 2 bridge-priority 16384

(IDF-1) (Global MSTP) #instance 1 vlan 100,200     

(IDF-1) (Global MSTP) #instance 2 vlan 300,400


  Above config makes VLAN 100,200 as part of MSTP "instance 1", and so on....


  And bridge-priority needs to be varied on other switches. In short, Bridge-priority (lower) decides which switch will be root-bridge for specific instance, (Refer MAS documentation for more details...)



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