While configuring Link Aggregation (LAG) using Link Aggregation Control Protocol (LACP) on the ISG you encounter unexpected results.
Link aggregation is unsupported on the ISG versions previous to 2.3.X.
Currently, Link Aggregation is unsupported on ISG versions previous to 2.3.X
For the 2.3.X versions support on Link Aggregation, please check the below ISG guides:
https://techdocs.broadcom.com/us/en/symantec-security-software/web-and-network-security/integrated-secure-gateway/2-3/About-ISG/manage-lags.html
https://techdocs.broadcom.com/us/en/symantec-security-software/web-and-network-security/integrated-secure-gateway/2-3/cli_Command-Line-Overview/cli_enable-mode-commands/cli_enable_lag.html