Friday, October 13, 2017

F5 DTLS edgeclient sslvpn

In this blog we will look at  DTLS setup for a F5 APM access-policy &  for remote-sslvpn clients.

To enable DTLS, you need to craft virtual-server and enabled  the  protocol UDP. Also within the Access Policy you have to enable the DTLS option.  The port you enable in the access-policy network-access  settings,  must match the virtual-server configuration for the destination-address.

Here's a simple Virtual-Server for support DTLS using the  connection profile

Notice: protocol UDP  and port 4433

The apm policy network resource needs the DTLS check box enabled and the defined service port which should match the ltm virtual server  service-port.  { access-policy > network-access > setting  }

If you monitor the  client access details from  the tmsh,  you will see no reference to  DTLS v1.0 being used directly.


But  to validate DTLS usage ,    monitor  the  statistics for the  ltm  profile  client-ssl profile, use the  grep to-match on DTLS.


When the edeg-client connect you will see the   edge-client statistics listing the connect as DTLS and the  cipher that's  in use for the session.

And the apm log message will display a output that's similar  when a client negotiates  a DTLS v1.0 connection.

  • if the client can't negotiate DTLS the  client will falback to  TLS.
  • beware of any forward proxies preventing   DTLS negotiation for port  4433 and udp
  • any local and remote firewall could prevent access to port udp.port == 4433
  •  initial contact is via  TLS but if the APM and client negotiate  DTLS the  data path will be switched to DTLS.

Ken Felix
NSE ( network security expert) and Route/Switching Engineer
kfelix  -----a----t---- socpuppets ---dot---com
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