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how GTM monitor work , what is the process of a GTM https montor

create monitor https m-test-host.c-name.test.doamin.com-HTTPS-8090 interval 15 timeout 60 send "HEAD /test.html HTTP/1.1\r\nHost: test-host.test.doamin.com:8090\r\n\r\n" recv "HTTP/1.[01] [23][0-9][0-9]" modify server server1 virtual-servers add { vs-dc1_test-host-8090 { destination 192.168.11.21:8090 } } exit exit modify server server2 virtual-servers add { vs-dc2_test-host-8090 { destination 172.16.5.12:8090 } } exit exit create pool a p-test-host.c-name.test.doamin.com modify pool a p-test-host.c-name.test.doamin.com members add { server1:vs-dc1_test-host-8090 { member-order 0 } } members add { server2:vs-dc2_test-host-8090 { member-order 1 } } monitor m-test-host.c-name.test.doamin.com-HTTPS-8090 load-balancing-mode global-availability alternate-mode none fallback-mode none max-answers-returned 1 ttl 10 exit exit exit create wideip a test-host.c-name.test.doamin.com { pools add { p-test-host.c-name.test.doamin.com } }

environment setting: a cname has been add:

  • test.host.test.domain.com test.host.c-name.test.domain.com
  • domain test.domain.com is configured to be resolved by the above GTM
  • GTM listen to the DNS resolve request for test.domain.com

 

I have a GTM configuration above , I am wondering how GTM https monitor works, here is my understandings, is that correct ?

  1. GTM detect the aliveness with test command: curl --insecure -v https://test-host.test.doamin.com:8090/test.html
  2. GTM send the DNS resolve request for test-host.test.doamin.com , since there is Cname , GTM will request DNS resolve for

test.host.c-name.test.domain.com

3. since the c-name.test.domain.com will be resolve by itself , GTM check the configuration , found that a pool is configured for

test-host.test.doamin.com

4, GTM check the pool member aliveness with command ,

curl --insecure -v https://192.168.11.21:8090/test.html

curl --insecure -v https://172.16.5.12:8090/test.html

if any of the pool member is up , the pool will be up , the wideip will be up.

2 REPLIES 2

rob_carr
MVP
MVP

In general, BIG-IP doesn't do name resolution as part of the monitor process, instead using the IP addresses defined for pool members, so you may only see the Step 4 traffic.

thank for your reply . if GTM doesn't request DNS resolution,what is the host in the monitor configuration used for ? ​ thanks .

create monitor https m-test-host.c-name.test.doamin.com-HTTPS-8090 interval 15 timeout 60 send "HEAD /test.html HTTP/1.1\r\nHost: test-host.test.doamin.com:8090\r\n\r\n" recv "HTTP/1.[01] [23][0-9][0-9]"