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gdoyle's avatar
gdoyle
Icon for Cirrostratus rankCirrostratus
Dec 19, 2019
Solved

TCP Health Check.

All, I have a customer who mentioned that they took a server down for maintenance, but were still receiving customer traffic.   This server sits in a pool tied to a VIP and is load balanced wit...
application delivery
big-ip
LTM
  • Leonardo_Souza's avatar
    Leonardo_Souza
    Dec 19, 2019

    TCP monitor will try a TCP handshake, if that is successful, marks pool member up.

    If you use the default TCP monitor, the alias address field is *, that means it will get the port from the pool member.

    So, if pool member is 192.168.1.1:639, it will try a TCP handshake with 192.168.1.1 on port 639.

     

    In the case you described, if the application itself was down, but the server still had the port TCP/639 open, the monitor will still mark the server up.

     

    You need an application layer monitor.

    The system has a built in LDAP monitor, so you should use that.

gdoyle's avatar
gdoyle
Icon for Cirrostratus rankCirrostratus
Dec 19, 2019

Thanks for the confirmation, Leonardo, and I concur about the use of an application monitor, unfortunately I did not architect their solution. I think the main cause in this case was that they decided to rely upon the health monitor to mark the pool as down while they did planned maintenance.