AirLive RS-2000 - Manual (Page 273)

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STEP 7﹒Select GRE/IPSec and enter GRE Local IP: 192.168.50.200. GRE Remote
IP: 192.168.50.100. (GRE Local IP must be at the same subnet (C
class))
STEP 8﹒Select Data Encryption+Authentication in IPSec Algorithm. You can
choose Data Encryption+Authentication or Authentication Only to
communicate:
ENC Algorithm: 3DES/DES/AES/NULL
AUTH Algorithm: MD5/SHA1
Here we select 3DES for ENC Algorithm and MD5 for AUTH Algorithm to
make sure the encapsulation way for connection.
STEP 9﹒After selecting Perfect Forward Secrecy and enter 28800 seconds in
IPSec Lifetime, but the Keep Alive IP field must be blank.