Switch BD 15.6 port peak utilzation moved to 100% only on 1 port in LACP

[Saurabh_Makkar]

1 port in LACP TX utilization is reaching 100%, average traffic on both these ports are 17% average.

MPGWLCTC> A 1000 4.09 100.00 8.05 100.00 --> 1:48
MPGWLCTC> A 1000 8.72 8.72 7.95 8.17 --> 2:48

Config Current Agg Ld Share Ld Share Agg Link Link UpMaster Master Control Algorithm Group Mbr State Transitions
==============================================================================
1:47 1:47 LACP L3_L4 1:45 - R 0
L3_L4 1:47 Y A 0
L3_L4 2:47 Y A 0
1:48 1:48 LACP L2 1:46 - R 0
L2 1:48 Y A 0
L2 2:48 Y A 0
========================================================================

Need to know what can be the cause and solution for the issue.

Customer says the services are not affected due to this, but my suspection is that some traffic is tweaked affecting peak utilization to 100% but only on 1 port.

[Saurabh_Makkar]

Hi Mrxlazuardin,

Thanks for sharing, also lets say if we increase 1 more in the LAG will it change anything ?

regards

Saurabh

[Mrxlazuardin]

Hi Saurabh,

On LACP especially if it consists only 2 ports, no matter hash algorithm you use on both side, can have possibility of mostly using one port if the hash algorithm result the same hash. This possibility can be higher if the combination of MACs, IPs and/or TCP/UDP ports (regarding to hash algorithm you use) is too small. For example, if the traffic is only about 2 servers connection with same TCP session (SCP transfer, etc.), the traffic will always use the same port. So, you should inspect your traffic first. L3+L4 hash algorithm can take advantage if the traffic is related to multiple IPs and multiple TCP/UDP ports due to the better hash result combination than L2 hash algorithm. For example is on connecting hypervisor server on virtualization where each node has multiple VMs with their own IPs and each VM has combined services related to their own TCP/UDP ports.

Best regards,

[Saurabh_Makkar]

1st Scenarion - l3-l4 working on router

2nd scenation - L2-L2 working on secondary Switch

[Nick_Yakimenko]

1st scenario also depends on the settings at the router's side

[Nick_Yakimenko]

Your 1:48 sharing is in L2 mode
That means if the source and destination mac are the same -- then traffic could not be distributed between all LACP ports

Change it to L3_L4