Forum Discussion
NimbostratusUDP Health Monitor SEND/RECEIVE STRING SYNTAX
Hi Expert,
I am in the process of configuring a LB application for SNMP agent server pool for a network monitoring tool. I wanted create a custom UDP health monitor. I was reading the following:
Its states that you only need the 2nd monitor if you do not implement a SEND/RECEIVE string in the monitors, but I cannot find any documentation on what type of receive string I could put together for this SNMP agent to send back. I do not want to place a generic udp and icmp monitor on the pool. Any help would be greatly appreciated.
MB
3 Replies
Leonardo_SouzaCirrocumulus
Interestingly, both UDP and TCP monitors have send and receive string. However, I never saw these monitors implemented with send and receive string.
I guess this would be useful if you know the application, so what text to send and what it would reply. Same idea as with HTTP/HTTPS monitor.
The idea for the second monitor (ICMP) is simple. If the host is there, and the port is down, it will reply and F5 will mark it down. If not there, it will not respond, and continue up. This is why you need ICMP to make sure the server is marked down when is not alive.
If you use a send and receive string, if the string is not receive, it is marked down after the timeout. In this case, you don't need the ICMP to cover the situation when the server is down.
Steven_J__WilliI have a UDP monitor probing my VIP/Pool for UDP 1812, and the nodes and pool show UP, but a netstat -a on one of the nodes does not list 1812 so how is it up exactly?
- Leonardo_Souza
Take a tcpdump to confirm the traffic is arriving in the server and the server is responding.
