Configuring Symmetric Trunk Hashing 

When a specific network design or monitoring device requires that the same trunk port be selected for all packets in both directions in a connection, starting from release 6.1.0 NetVisor OS supports the Symmetric Trunk Hashing mode. 

Note that:

  • Symmetric hashing is agnostic to intrinsically unidirectional parameters, such as the ingress physical interface.
  • Symmetric hashing mode is an alternative configuration to the default (asymmetric) mode.
  • Configuring symmetric hashing does not require a switch restart.
  • You can configure symmetric hashing on a single switch or on all switches of a fabric by prepending the command with switch*.

To configure symmetric hashing, use the following per-device system command:

CLI (network-admin@switch) > system-settings-modify <symmetric-hash | no-symmetric-hash>

Where, the symmetric-hash parameter enables symmetric trunk hashing on the switch. By default, this feature is disabled. If enabled, you can use the no-symmetric-hash parameter to disable it.

To configure symmetric hashing on all switches in a fabric, use the command:

CLI (network-admin@switch) > switch * system-settings-modify <symmetric-hash | no-symmetric-hash>

In case of GRE or IPSec traffic, ignoring the unidirectional GRE key or IPSec SPI fields in the symmetric hash computation can be configured using the CLI:

CLI (network-admin@switch) >  system-settings-modify <hash-suppress-unidir-fields | no-hash-suppress-unidir-fields>

This feature is disabled by default, using the no-hash-suppress-unidir-fields parameter.

To verify the configuration details, use  the system-settings-show command. Below is a sample output, where both symmetric-hash and hash-suppress-unidir-fields parameters are disabled.

CLI (network-admin@switch) > system-settings-show layout vertical

switch:                                switch

optimize-arps:                         off

lldp:                                  on

policy-based-routing:                  off

optimize-nd:                           off

reactivate-mac:                        on

reactivate-vxlan-tunnel-mac:           on

manage-unknown-unicast:                off

manage-broadcast:                      off

block-loops:                           off

auto-trunk:                            on

auto-host-bundle:                      off

cluster-active-active-routing:         on

routing-over-vlags:                    off

source-mac-miss:                       copy-to-cpu

igmp-snoop:                            use-l3

vle-tracking-timeout:                  3

pfc-buffer-limit:                      40%

cosq-weight-auto:                      off

port-cos-drop-stats-interval(s):       disable

lossless-mode:                         off

snoop-query-stagger:                   no-stagger-queries

host-refresh:                          off

proxy-conn-retry:                      on

proxy-conn-max-retry:                  3

proxy-conn-retry-interval:             500

manage-l2-uuc-drop:                    on

xcvr-link-debug:                       disable

fastpath-bfd:                          off

linkscan-interval:                     150000

linkscan-mode:                         software

single-pass-l2-known-multicast:        off

single-pass-flood:                     off

batch-move-mac-hw-group-for-vlan-only: off

memory-tracker:                        on

symmetric-hash:                        off

hash-suppress-unidir-fields:           off