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4500-X VSS with U shaped topology



Due to some requirement i need to connect the 3560-X in U shaped topology with 4500-X vss. My design is as follows (see attached):

1. VSS is the STP and HSRP root

2. Link between 4500-X to 4500-X VSL link is 20G (2x10G portchannel)

3. Link from 3560-X to 4500-X is 10G

4. Link between 3560-X to 3560-X is 2G (2x1G portchannel)

5. 3560-X access ports will be connected to Phones and then to laptop. Phones support only 100Mbps!.

Ideally STP should block the link between the 3560-X and all the traffic will flow through 10G uplinks. I understand the traffic will traverse the VSL link on 4500-X switch. During failure of any 10G uplink STP will converge and the 2G link will be open for traffic flow.

I need to connect 10 pairs of 3560-X access switches in this model. Are there any issues or limitations with this topology? Any specific things to be configured for STP?

Your ideas and thoughts are really appreciated.


3 Replies 3

Reza Sharifi
Hall of Fame Expert Hall of Fame Expert
Hall of Fame Expert

You don't need to connect the 3560 switches together as long as you are putting both uplinks in one portchannel. You currently have the 3560 Connect to only one switch you need to connect each 3560 to both 4500 switches and eliminate the link between 3560s
Also there in no limitation as to how many switches you can connect to the VSS pair as long as you have enough port


Sent from Cisco Technical Support iPhone App

Hi Reza,

Thanks for your reply.. But if i don't connect the 3560 together i dont hv any alternate link when my uplink fails.. This is one of my requirement and i dont want each 3560's to have dual uplinks.

Sufficient ports are there in 4500. My question is on STP, bandwidth issue, VSL link congestion etc..


Remember, since you are using VSS, if you connect each 3560 with 2 10Gig uplink to each 4500, there in no Spanning tree since both 4500 switches are logically one and not 2.  So it is as connecting one switch to another.

Before connecting your access switches together, I  suggest you take a look at VSS pratcice deployment.


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