Forum Discussion
JG
Cumulonimbus
CumulonimbusPool members with fully-qualified domain names (FQDNs): How does this work?
From release notes of v11.6.0 (on new features):
Populate pools by FQDN This release includes the ability to configure a BIG-IP system with nodes and pool members that are identified with fully-qualified domain names (FQDNs). When configuring pool members with FQDN, addresses dynamically follow DNS changes. Fully dynamic DNS-managed pools may even be created.
How does this work? When the fqdn resolves to multiple addresses, how is LB handled?
Brad_Parker_139Nacreous
The FQDN node list will auto populate all the nodes that are returned by the DNS query; they are called ephemeral nodes. You need to make sure your DNS server is set to return all A records for this to occur.
JGThanks for your response. Does this mean that the total or maximum number of pool members/nodes is determined from the initial DNS query of the fqdn made at the time of pool creation, i.e. the number of A records returned? And just how ephemeral are these pool members/nodes? Are all subsequent DNS queries based on the TTL of the records? There should be a sol article to give us more details about this.- Brad_Parker_139I've actually been playing with this in our test environment. The nodes will be created at the time of the original DNS query, however you can configure the LTM to auto populate and you can choose the interval that the LTM re-queries DNS. By default auto populate is on and re-checks once an hour. If an IP is not returned that was originally it will be removed and subsequently, if a new IP is returned it will be added. I hope this helps. https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-11-6-0/32.print.html
Brad_ParkerCirrus
The FQDN node list will auto populate all the nodes that are returned by the DNS query; they are called ephemeral nodes. You need to make sure your DNS server is set to return all A records for this to occur.
- JGThanks for your response. Does this mean that the total or maximum number of pool members/nodes is determined from the initial DNS query of the fqdn made at the time of pool creation, i.e. the number of A records returned? And just how ephemeral are these pool members/nodes? Are all subsequent DNS queries based on the TTL of the records? There should be a sol article to give us more details about this.
- Brad_ParkerI've actually been playing with this in our test environment. The nodes will be created at the time of the original DNS query, however you can configure the LTM to auto populate and you can choose the interval that the LTM re-queries DNS. By default auto populate is on and re-checks once an hour. If an IP is not returned that was originally it will be removed and subsequently, if a new IP is returned it will be added. I hope this helps. https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-11-6-0/32.print.html
- Mauricio_01_142
Nimbostratus
Hello I added first the domains needed in System>Configuration>Device>DNS. Then I created nodes using FQDN name. Then for the pool (already created) I added the nodes from FQDN list and removed the old ones using IP address. I was able to notice that for each FQDN node added to the pool, another node is created below with IP address as well. I am not sure if this is expected. Can somebody confirm this?
I have another question, f5 saves caché for DNS entries? as we are working on a DR plan, I would expect the f5 resolves the name to the new IP when DR plan renames the DNS entry to point to another server
- Mauricio_01_142
LB does a DNS lookup on a default value of 3600 seconds, this can be configured on the same FQDN node, I set it to 60 seconds and worked fine. So I don´t have to worry about the caché. BTW DR plan worked awesome. FQDN nodes are able to resolve the IP addresses fine, but it would until the DNS has the updated entry first. SO it can take some time regarding the geolocation. Hope this can help