Overriding Host Header in Health Monitor

By default,
NSX Advanced Load Balancer
appends additional HTTP headers (Host, User-Agent and Accept) into HTTP health monitor requests.
The exact values of these headers are as follows:
Header
Values
User-Agent
avi/1.0\r\n
Host
<hostname>\r\n
Accept
*/*;\r\n\r\n
For instance, if an
NSX Advanced Load Balancer
admin (user) adds a Host header in HTTP client request data field of a health monitor,
NSX Advanced Load Balancer
will send this additional Host header together with the existing Host header (Host header inserted by
NSX Advanced Load Balancer
).
You can prevent from adding additional Host header. Use Exact Request option on
NSX Advanced Load Balancer
UI or use_exact_request flag in
NSX Advanced Load Balancer
CLI for a health monitor instructs
NSX Advanced Load Balancer
to pass the exact HTTP request string as specified by
NSX Advanced Load Balancer
admin (user), without any automatic insertion of the additional HTTP headers. This indicates that user is now responsible for adding the appropriate headers to the HTTP client request field.

Configuration from
NSX Advanced Load Balancer
CLI

Login to
NSX Advanced Load Balancer
CLI, and use configure healthmonitor System-HTTP command to change the value of the flag
exact-http-request
.
[admin:10-1-1-1]: > configure healthmonitor System-HTTP [admin:10-1-1-1]: healthmonitor> http_monitor [admin:10-1-1-1]: healthmonitor:http_monitor> http_request [admin:10-1-1-1]: healthmonitor:http_monitor> http_request "HEAD / HTTP/1.0\r\n\r\n" Overwriting the previously entered value for http_request [admin:10-1-1-1]: healthmonitor:http_monitor> exact_http_request Overwriting the previously entered value for exact_http_request [admin:10-1-1-1]: healthmonitor:http_monitor> [admin:10-1-1-1]: healthmonitor:http_monitor> save [admin:10-1-1-1]: healthmonitor> save

Configuration from
NSX Advanced Load Balancer
UI

  1. Navigate to
    Templates
    Profiles
    Health Monitors
    .
  2. Choose the desired HTTP health monitor and click
    edit
    icon.
  3. Select the check box for
    Use Exact Request
    .
  4. Click
    Save
    .