last person joined: 12 hours ago 

Expand all | Collapse all

6300 LACP symetric traffic

This thread has been viewed 16 times
  • 1.  6300 LACP symetric traffic

    Posted Feb 09, 2021 12:06 PM


    I need to create a symetrical bundle using LACP. I need to balance traffic in 2x10G links but I must be sure that a packets for a flow identified by SRC_IP=A and DST_IP=B go upstream and downstream for same link. For example, the LACP hash algoritm will use SRC_IP=A and DST_IP=B to chose a link to go upstream. Other switch should chose the same link for downstream. In this case, SRC_IP=B and DST_IP=A. is it possible?.

    Thanks in advanced.


    Antonio Guirado

  • 2.  RE: 6300 LACP symetric traffic

    Posted Feb 14, 2021 05:35 AM
    Hi Antonio, I believe LACP were not engineered to guarantee that INCOMING received packets (of the same message/session) will use the same EGRESS port of the sending switch that was used by sent messages of that very same originating message/session...you're asking a sort of "sticking mechanism" for the BOTH the outgoing (which can be reasonable) AND INCOMING data flows (generally such of a sticking mechanism - at least when implemented in Firewalls, as example - is used to guarantee that packets of the same message will use the same OUTGOING interface to reach their common destination...typical when you have a Firewall with Dual WAN and you need that a particular session hits a particular WAN link without flip-flop between WANs).

    Static or LACP aggregations (Port Trunks/LAGs) work with the switch distributing its OUTGOING packets on its aggregated ports...thus the switch implementing Static/LACP aggregated interface has no control on the data traffic it RECEIVES back from the upstream switch it is connected to (that peer switch indeed controls its OUTGOING traffic autonomously, traffic you want to receive back on the very same Static/LACP LAG/Port Trunk).

    Post your doubts/requests/issues on the Airheads Wired Intelligent Edge sub-forum otherwise you're at risk your post to pass unnoticed here in this part of the forum.

    Davide Poletto

  • 3.  RE: 6300 LACP symetric traffic

    Posted Feb 14, 2021 12:10 PM

    yes, it is true. I have studied Cisco, Juniper, Huawai and there is a feature named Symmetric hashing to be sure that forward and reverse traffic use the same link in a LACP bundle. Do you know if Aruba has this feature?.


    Antonio Guirado

  • 4.  RE: 6300 LACP symetric traffic

    Posted Feb 14, 2021 04:59 PM
    I fear that a similar feature is not (explicitly) available on ArubaOS-CX operating system...we have to consider that, anyway, it requires similar if not identical peer switches both supporting it and it is required to be implemented on both ends of the aggregated links.

    To be honest, to me it looks probably a feature required when traffic is locally (on the originating switches) subject of some sort of DPI...as Juniper explains quite well...AFAIK ArubaOS-CX hasn't such firewall typical feature (DPI) so it would explain why it was not implemented.