Root Guard on vlan interfaces

[mbagnes]

Hi, community,

I have some doubts about the feature Root Guard. My scenario is four VLANs on two distribution switches and some access switches connected to the upper layer. Switch A is the root bridge for VLANs 1 and 2, while Switch B is the root bridge for VLANs 3 and 4. 

So, if I enable Root Guard on the physical interface on Switch A, it will cause problems with BPDUs for VLANs 3 and 4, leading to the interface being blocked.  The IOS allowed me to configure Root Guard on the VLAN interface, but it didn't work as expected in GNS3 when I tested. 

My concern is that I don't know if it`s a bad conf or the image doesn't work properly. Thanks in advance.

[MHM Cisco World]

Sorry but I dont see SW-A

MHM

[mbagnes]

Sorry, my mistake. Switch A = B-00-SW01, and Switch B = B-00-SW02

[MHM Cisco World]

Root guard make issue if you config it in B00SW1/2 

You need to config it one layer down in B01-B02-B03 in link connect these SW to access SW.

MHM

[MHM Cisco World]

 

[paul driver]

Hello
Really you only would require root guard on interconnect links between 2 differing stp domains, so you can control the root ports between those stp domains, But within a single stp domain , not sure its really required as you would want fail over to happen in the event you lost some links on the root switch(s) and not isolation of those links