How static IPs are used in Windows Failover Cluster and HAG listeners?

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How static IPs are used in Windows Failover Cluster and HAG listeners?

artisticcheese

Right there with Babe

Points: 751
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February 17, 2018 at 8:20 am

#410250

Hello,
Can somebody answer following questions. I have 2 Azure VMs with HAG setup but no HAG listeners are setup. The reason being I'm confused where those static IPs are supposed to come from and if they are needed in a first place.
Questions:
1. Why do I need HAG listener at all if I can just use IP address of each host to connect to SQL
2. If add additional IP addresses, are those supposed to be manually added to TCP/IP properties of adapter or WSFC will take care of that during failover
3. What is difference between using HAG DNS name vs just using database mirroring type (Data Source/Failover Partner) connection string. They seemed to be doing the same thing, i.e. providing alternative IPs where service is being hosted
4. Does WSFC needs to have "Server Name" under core cluster resources? What is the point of that name in terms of HAG functionality? Can I just delete it?

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Henrico Bekker One Orange Chip Points: 27652 More actions · Answer 1

Start with Perry's Stairway to AlwaysOn, will answer all your questions: http://www.sqlservercentral.com/stairway/112556/

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This thing is addressing problems that dont exist. Its solution-ism at its worst. We are dumbing down machines that are inherently superior. - Gilfoyle

Perry Whittle SSC Guru Points: 234013 More actions · Answer 2

artisticcheese - Saturday, February 17, 2018 8:20 AM
Hello,
Can somebody answer following questions. I have 2 Azure VMs with HAG setup but no HAG listeners are setup. The reason being I'm confused where those static IPs are supposed to come from and if they are needed in a first place.
Questions:
1. Why do I need HAG listener at all if I can just use IP address of each host to connect to SQL

You don't need to use a listener for your Availability Group, there's nothing forcing you too, it's optional.
But if you want to start directing read only queries to any secondary replicas then this is a pre requisite.

artisticcheese - Saturday, February 17, 2018 8:20 AM
2. If add additional IP addresses, are those supposed to be manually added to TCP/IP properties of adapter or WSFC will take care of that during failover

Extra networks are configured by adding NICs to the servers, the cluster subsystem will pick up the extra networks available, always run a cluster validation any time you change the cluster configuration ( such as adding new hardware and networks )

artisticcheese - Saturday, February 17, 2018 8:20 AM
3. What is difference between using HAG DNS name vs just using database mirroring type (Data Source/Failover Partner) connection string. They seemed to be doing the same thing, i.e. providing alternative IPs where service is being hosted

Database mirroring failover partner is not valid here so do not concern yourself with it.
If you have a listener configured then you use this to connect to the group, if you configured a port other than TCP 1433 you also need to specify the port number too.
For example listener name of MYAGGROUP and TCP port 1503 would require

MYAGGROUP, 1503

artisticcheese - Saturday, February 17, 2018 8:20 AM
4. Does WSFC needs to have "Server Name" under core cluster resources? What is the point of that name in terms of HAG functionality? Can I just delete it?

Do not delete any of the core cluster resources, do not touch the configuration in any way

Please read my stairway before you go any further!

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"Ya can't make an omelette without breaking just a few eggs" 😉

artisticcheese Right there with Babe Points: 751 More actions · Answer 3

Thank you for your response. I did read your write up, just was unable to deduct my questions from it.
I did not fully understand response about using HAG listener in connection string as opposed database mirroring type connection string. HAG listener IP address relies on DNS to forward traffic to active node as far as I understand while specifying Principal/Failover partner provides 2 IPs of both nodes and client decides which one to connect to. I have running HAG and using Principal/Failover type connection string and it works perfectly fine with no requirement for HAG listener to be setup at all and fails over as expected (https://www.youtube.com/watch?v=q13AWFoK0tg)
This provides much less overhead to setup and maintain then HAG listener at least for me and I don't understand the point of having HAG listener at all unless you have more then 2 nodes since it seems to be doing the same thing just on DNS level.

Perry Whittle SSC Guru Points: 234013 More actions · Answer 4

artisticcheese - Wednesday, February 28, 2018 8:08 AM
HAG listener IP address relies on DNS to forward traffic to active node as far as I understand

No, DNS host record just sends the connection to a defined location requesting a name resolution as it does with any lookup.
The response is handled by whichever instance is primary and is controlled by the sql server AG and the cluster subsystem

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"Ya can't make an omelette without breaking just a few eggs" 😉