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Beginner

MEC from VSS pair to access switch

Dual homed to VSS.png

 

 

 

 I have 2 6807 chassis Core1 and Core2 joined via VSS and connected via MEC to access Switch 1. Server 1 is connected to Core 1 and PC 1 - 3 connected to Switch 1. When I run iPerf between Server 1 and the 3 PC's I get different paths depending on the direction. When the traffic flow is from the PC's to Server 1 the traffic utilizes both links in the multichassis etherchannel and I see 2 GB/s speeds. However, when the direction is from Server 1 to the 3 PC's the traffic only utilizes the C1 - SW1 side (G1/1/1 to G1/3) and ignores the C2 - SW1 side of the channel.

 

Unfortunately, when imaging a classroom the traffic is from Server 1 to the PC's and that is when I want to utilize the full 2 Gb/s bandwidth of the etherchannel. Can anyone tell me why this is and if there is a way to make traffic flow across both links when going from Server 1 to the PC's?

 

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VIP Advisor

Re: MEC from VSS pair to access switch

Since end device Server connected to 1 switch all the flows should go to end point where the Server terminated port only, even though you want to LB the traffic across switch, this can not be achieved.

 

suggest is add 1 more interface to server and connect to C2, so you have best performance in terms of service.

 

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Beginner

Re: MEC from VSS pair to access switch

That is interesting because the VSS-Enabled Campus Design document, it says: "As described above, in a normal mode, the VSS always prefers locally-attached links."  This leads one to believe there is a alternate mode that allows you to override the default behavior and utilize the VSL for load-balancing.  Is anyone familiar with this scenario and whether it is possibly an undocumented capability?  Everything that I can find about this indicates that the feature/behavior is "default", which indicates it is not "fixed" but a variable setting.  Wondering if someone with like 17 badges can confirm this? ;)

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