GLBP with STP

[jason.suplita]

I have been reading about GLBP and it had one access layer switch with a vlan that was trunked to three separate distribution switches. It had the data from that one vlan evenly distributed across all three distribution switches. My question is how does this work in with STP? If one switch is the primary root switch, and it is the distribution switch, then wouldn't all the traffic on the vlan route only to that one primary root switch instead of the other two? One way I can see this working is if the access switch is the primary root switch, since all traffic to that vlan would be destined for that switch, assuming that, that vlan is unique only to that one access switch. Or do you configure the AVG as the primary root switch for that particular vlan since all arp requests are answered by the AVG switch. Am I understanding this right or can someone enlighten me to how this works in.

[nambi_gct]

Hi,

GLBP is used as first hop redundancy protocol like(not exactly) HSRP or VRRP.In your topology I assume that your access layer has L2 switches and distribution layer has L3 devices.You are expecting load sharing between access and distribution layer which is purely an L2 connection.But GLBP provides redundancy in cases where you have many first hop routers.It distributes the L3 decisions load at the first hop.

Thanks

Nambi.