03-12-2007 06:39 PM - edited 03-05-2019 02:51 PM
Can someone tell me if having the same VLAN that spans multiple switches and connects to dual distributions really works with GLBP???
I have two interconnected distribution switches (Distribution-A and Distribution-B) that have multiple access layer switches (access-A & access-B) connected to each distribution switch. Each access layer switch has the same VLAN (Vlan2) across both switches. .
Please take a look at this PDF:
http://www.cisco.com/application/pdf/en/us/guest/netsol/ns432/c649/cdccont_0900aecd801a8a2d.pdf
On page 40, figure 41 - with VLAN 2 present on two access layer switches, and both switches are uplinked to the two distribution switches.
In this configuration, wouldn't one of the uplinks on Distribution switch B be blocked not only on the link that connects to distribution-A and also to one of the access layer switches.
I don't see how GLBP can work if you have dual distribution switches connected to multiple access layer switches that span Vlans. This document seems wrong
Can someone correct me if I?m wrong.
03-16-2007 11:57 AM
STP can be used for L2 load balancing which acn be done using spanning-tree and multiple-vlans, and with etherchannels. If you have 2 uplinks, 1 vlan would be fwd in 1 link, and 2nd vlan would be fwd in the 2nd link.
Following link may help you
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800ae96a.shtml#intro_vlan
GLBP, used at layer 3, Load balancing is achieved with up to 4 gateways on the same subnet , sharing the same IP but with different virtual macs.
Following link may help you
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hiap_c/ch20/haipglbp.htm
03-16-2007 06:27 PM
You are correct. I believe the diagram is in error. Access switch A should have a different vlan than Access switch B, and there should be a L3 connection between the two distribution boxes. GLBP works best when there is only one subnet per switch/closet (no vlan spanning). HSRP makes more sense when spanning vlans across multiple switches and remember to match the STP root with the HSRP active gateway.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide