glbp priority parameter affects which device will become the AVG. Remember there is only one AVG and it is the device that assigns the virtual MAC address to all other devices running GLBP. Priority has nothing to do with which how data traffic will be forwarded.
glbp weighting parameter on the other hands, is used to determine if a device will become an AVF. Remember there are multiple AVFs in a GLBP group, and an AVF is simply a device that will forward traffic. So weighting ultimately affects the number of available devices through which traffic can be forwarded.
Concerning the wireshark captures that contain the frames designated with the “loop” protocol, this doesn’t necessarily mean that you have a loop in your topology.
The Loop protocol, more correctly referred to as the Ethernet Configuration Testing Protocol (CTP) is an obscure protocol that has been part of Ethernet since it’s inception by the DEC/Intel/Xerox consortium created the Ethernet v2.0 specification. It’s not even defined at all within any of the IEEE 802 specs. It is a protocol that can be considered as a layer two ping equivalent. Some more information about it can be found here:
It can be thought of as an Ethernet keeplaive message that can be used to detect loops. As you can see all loop frames have the same source and destination MAC addresses. It is used to detect self-looped ports. If a switchport receives a loop frame it sent to itself, it would be put in err-disabled state. It has been found however by some users that the loop protocol is actually ignored by some platforms while others still use it.
Now it is interesting that you see these frames in your ports. This gives me the impression that you have not configured the ports on the switches connected to the router as routed ports. So the “router facing” ports on the switches should be configured as routed ports (i.e.
no switchport). This way no loop protocol frames will be seen on these ports. Also, do some troubleshooting with STP to see if there are any blocked ports to see if you actually do have any physical L2 loops. Based on the topology, there should be no ports blocked by STP.
Take a look at those aspects of the topology to continue your troubleshooting, and let us know if there are additional questions that come up.
I hope this has been helpful!