Module 2 - Virtual Server and Pool Behavior and Status

Virtual Server Status

Test Disabled Virtual Server

Q1. What is the Availability of www_vs? What is the State?

Availability: available, State: disabled

Q2. What symbol is used to represent www_vs status?

Black Circle

Q3. Would you expect browsing to http://10.1.10.100 to work?

No

Q4. Can you ping the virtual IP?

Yes, the virtual address still responds to pings

Q5. Did the site work? What did the tcpdump show?

No, the tcpdump showed the virtual server 10.1.10.100:80 responding to SYNs with Resets

Q6. Did statistics counters for any virtual increment?

No

Q7. Why do you think the wildcard_vs didn’t pick up the packets?

www_vs was the most specific virtual server so it responded. Because the www_vs was disabled the response was to reset the connection. This make sense if you think about it. What good would it do to disable a virtual server just to have another virtual server pick up the traffic either process incorrectly or send it to servers you just tried to prevent traffic from going too.

Q8. What symbol is used to represent wildcard_vs? Why is symbol a square?

The status symbol is a black square. Black because the virtual server was administratively disabled and square because there is no monitor and the state is Unknown

Q9. What is the reason given for current state?

The children pool member(s) either don’t have service checking enabled, or service check results are not available yet. Availability: unknown State: disabled

Q10. Does ftp session still work? Why?

Disabling a configuration item (node, pool or virtual server) does not affect existing connections.

Q11. Did new ftp session establish connection? Why not?

No, a disabled virtual server will not process new connections.

Virtual Server Connection Limits and Status

Q1. Does ftp session work?

Yes

Q2. What is the virtual server status of ftp_vs?

Yellow Triangle - Availability: unavailable - State: enabled

Q3. Did new ftp session establish connection? Why not?

No, the virtual server’s connection limit has been reached.

Q4. Did tcpdump capture show a connection reset?

Yes, tcpdump revealed R TCP reset the connection.

Q5. Quit all FTP sessions and note ftp_vs status.

Once all the FTP have been terminated and you have drop below the maximum connection limit the virtual server should become Available

Pool Member and Virtual Servers

Effects of Monitors on Members, Pools and Virtual Servers

Q1. Since the mysql_monitor will fail, how long will it take to mark the pool offline?

60 seconds, the monitor will have to fail 4 times at 15 second intervals before it exceeds the 46 second timeout value.

Q2. What is the icon and status of www_vs?

Red Diamond - Availability: offline - State: enabled - The children pool member(s) are down

Q3. What is the icon and status of www_pool?

Red Diamond - Availability: offline - State: enabled - The children pool member(s) are down

Q4. What is the icon and status of the www_pool members?

Red Diamond - Availability: offline - State: enabled - Pool member has been marked down by a monitor

Q5. How does the status of the pool configuration effect the virtual server status?

The status of the pool members can affect the status of the virtual server. If all the the pool members are offline, then the pool is offline and therefore the virtual server goes offline.

Q6. What is the icon and status of www_vs?

Black Diamond - Availability: offline - State: disabled - The children pool member(s) are down

Q7. Did traffic counters increment for www_vs?

No

Q8. What is the difference in the tcpdumps between Offline (Disabled) vs Offline (Enabled)?

Offline (Disabled) - immediate connection reset, you will see no virtual server statistics.

Offline (Enabled) - initial connection accepted then reset, the virtual server stats are incremented

More on status and member specific monitors

Q1. What is the status of the Pool Member and the monitors assigned to it?

Red Diamond - Red Diamond - Availability: offline - State: enabled - Pool member has been marked down by a monitor

http - Green Circle, mysql_monitor - Red Diamond

Q2. What is the status of www_vs, www_pool and the pool members? Why?

Green, Green, Red, Red, Green. One pool member available, marks the pool available and since the pool is available, the virtual server is available

Q3. Did the site work?

Yes

Q4. Which www_pool members was traffic sent to?

Traffic was distributed to availble pool members.

Load Balancing

Load Balancing

Q1. Which www_pool members was traffic sent to?

Traffic was distributed to 10.1.20.12 and 10.1.20.13

Q2. Did member 10.1.20.12 receive the most traffic? Why not?

No, because LB method is Round Robin, Ratio and Priority Group configurations on pool members do not apply.

Q3. Which www_pool members was traffic sent to?

Traffic was distributed to 10.1.20.12 and 10.1.20.13

Q4. Did member 10.1.20.12 receive the most traffic?

10.1.20.12 received 5x more traffic than 10.1.20.12

Priority Group Activation

Q1. Which www_pool members was traffic sent to?

Traffic was distributed to 10.1.20.11 and 10.1.20.12

Q2. Which www_pool members was traffic sent to? Why?

Traffic was distributed to 10.1.20.12 and 10.1.20.13. Pool member availability dropped below 2 available members in the highest priority group and the next lowest priority group was activated.

Q3. Would the results have been different if 10.1.20.11:80 had been marked offline or marked with a yellow triangle?

No, both mark the member as Unavailable, dropping the Available members below 2.

The Effects of Persistence on Load Balancing

Q1. Why was a http profile required?

The http profile was required to tell the BIG-IP to parse the http request/response sequence for the virtual server so it could insert and read cookies in the http headers.

Q2. Was traffic evenly distributed to all www_pool members? Why not?

Traffic went to only on pool member because of persistence,

Q3. Did you persist to the Disabled member? Why?

Yes, a Disable pool member will still receive new connections if a persistence record points to it.

Q4. Does traffic continue to persist to the member Forced Offline?

No, another available member was selected and a new persistence record was created

Q5. If cookies were disable on your browser would persistence still work? Why?

Yes, source address persistence would be used to persist to a pool member