Technical Tip: Verify link aggregation (LAG, LACP, 802.3ad) algorithm result

[anakamura]

Description

This article describes how to check which physical port will be used within a LAG based on the hash value calculation.

Note:

This command will show the port which is selected by software hash calculation, while a different port selected by NP6 on any NP6 platforms can actually be used.

Solution

Verify which port will be used in LACP LAG.

diagnose netlink aggregate port <aggregate-interface>
[ src-mac <mac-addr> ] [ dst-mac <mac-addr> ]
or
[ src-ip <IPv4-addr> ] [ dst-ip <IPv4-addr> ] [ proto <IP-protocol> ] [ src-port <TCP/UDP port> ] [ dst-port <TCP/UDP port> ] [ vlan-id <VLAN-Id> ] [ spi <IPsec-SPI> ] [ frag (offset|flag) ]

Example for L4 hash (default):

diag netlink aggre port agg2 src-ip 1.2.3.4 dst-ip 5.6.7.8 proto 6 src-port 64123 dst-port 64124
 > port port4
diag netlink aggre port agg2 src-ip 1.2.3.4 dst-ip 5.6.7.8 proto 6 src-port 64120 dst-port 64125
> port port2

Example for L3 hash:

diag netlink aggre port agg2 src-ip 1.2.3.4 dst-ip 5.6.7.8
 > port port2
diag netlink aggre port agg2 src-ip 1.2.3.4 dst-ip 5.6.7.9
 > port port4

Example for L2 hash:

diag netlink aggre port agg2 src-mac 00:10:10:20:30:40 dst-mac 00:50:56:57:58:59
 > port port4
diag netlink aggre port agg2 src-mac 00:10:10:20:30:40 dst-mac 00:50:56:57:58:60
 > port port2

Note: By default in FortiOS, LAG member selection algorithm for traffic distribution is based on ONLY Layer 4 header information.

Clarification:

• The L2 algorithm ONLY considers the Source and Destination MAC addresses when distributing the traffic across the port members of the LAG.
• The L3 algorithm ONLY considers the Source and Destination IP addresses when distributing the traffic across the port members of the LAG.
• The L4(default) algorithm ONLY considers Source and Destination ports (TCP/UDP) when distributing traffic across the port members of the LAG.
• The source-MAC algorithm ONLY considers the Source-MAC address when distributing the traffic across the port members of the LAG.

Related articles:

Technical Tip: Initial troubleshooting steps for LACP (Link Aggregation - 802.3ad)