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Nexus 9300 - LACP Load-Balancing

oguarisco
Participant
Participant

Dear all,

In a situation where DC1 is connected to DC2, with 8x 10G links in LACP mode (vPC) for a total of 80Gbit/s with LoadBalancing method "souce IP and destination IP". Both DCs are based on 2x Nexus 9300 in a vPC Domain.

Supposing to have a single traffic flow of more than 10G, what will happen?
Is the rest of the traffic exceeding 10G dropped due to Load-Balancing method used?

BR

Omar

2 Accepted Solutions

Accepted Solutions

Dawei
Cisco Employee
Cisco Employee

you're right. A flow will be hashed to a link, and excess packets will be dropped.

View solution in original post

Rotate is used to avoid the multi-layer hash polarization problem.

The same flow has the same L3 and L4 header, it's hard to hash to different link. On the other hand, If one flow hashed to different links, it will cause other problems such as TCP out of order.

View solution in original post

3 Replies 3

Dawei
Cisco Employee
Cisco Employee

you're right. A flow will be hashed to a link, and excess packets will be dropped.

Hello Dawei,

thanks for the feedback/confirmation... is there a way to optimize the LB algoritm?
At the moment we're using L3-L4... but I've noticed on the command there is the argument "rotate 0".
The rotate could not help in case of excess packets or is it only a randomizing hash to rebalance traffic already balanced?

 

Rotate is used to avoid the multi-layer hash polarization problem.

The same flow has the same L3 and L4 header, it's hard to hash to different link. On the other hand, If one flow hashed to different links, it will cause other problems such as TCP out of order.

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