Configuring the BIG-IP System to Auto-Populate Pools
Overview: Using host names to identify pool members and nodes
You create nodes on the BIG-IP system to represent the backend servers on
your network. In turn, you create pool members to represent the backend servers on your network
when you create a pool and want to load balance traffic to multiple backend servers.
You can configure a BIG-IP system with nodes and pool members that are identified with
fully-qualified domain names (FQDNs). When you configure pool members with FQDN, addresses will
dynamically follow DNS changes. Fully dynamic DNS-managed pools may even be created. In the
following illustration, the BIG-IP Local Traffic Manager creates an
ephemeral pool member for each IP address returned in the DNS response.
BIG-IP system auto-populating a pool and routing traffic to the pool members
This next illustration shows another option. With this configuration, the
system sends a DNS query for the FQDN, and then creates only one ephemeral node or pool
member using the first IP address returned in the DNS response. An advantage to this
configuration is that you can change the IP addresses of the backend servers that host the
domain without reconfiguring the BIG-IP system. If your DNS servers are configured to round
robin the DNS responses, be sure that the DNS servers return all available.
BIG-IP
system routing traffic to a node identified by a host name
About modes of failure and related nodes or pool members
If a node or pool member that is identified by a fully-qualified domain name (FQDN) is down
for a specified amount of time, the BIG-IP system marks the node or pool member down.
Failure to resolve a FQDN will not cause the marking down of nodes or pool members currently in service.
While the status of the FQDN node or pool member for DNS is reflected in the status of the FQDN node,
since the FQDN node or pool member does not itself monitor any servers,
its status does not contribute to the status of the pool in any way.
Failure of a monitored ephemeral to respond to monitor probes results in the marking down of a specific node.
Niether the FQDN or any of the related ephemeals are directly affected.
Because ephemeral objects monitor servers, the status of the epemeral node or pool member
affects the pool status in the same way as any other pool member or node.
Task summary
for configuring BIG-IP auto-populate pools
Perform these tasks to configure the system to auto-populate
pools.
Creating a default gateway pool
Create a default gateway pool for the system to use to forward
traffic.
On the Main tab, click
Local Traffic
Pools
.
The Pool List screen opens.
Click
Create
.
The New Pool screen opens.
In the
Name
field, type a unique name for the pool.
For the
Health Monitors
setting, from the
Available
list, select the
gateway_icmp
monitor and move the monitor to the
Active
list.
Using the
New Members
setting, add each router that you want to include in the default gateway pool:
Type the IP address of a router in the
Address
field.
Type an asterisk (
*
) in the
Service Port
field, or select
*All Services
from the list.
Click
Add
.
Click
Finished
.
Configuring the
BIG-IP system to handle DNS lookups
Configure how the BIG-IP system handles DNS lookups when you want to use
fully-qualified domain names (FQDNs) to identify nodes and pool members.
On the Main tab, click
System
Configuration
Device
DNS
.
The DNS Device configuration screen opens.
In the DNS Lookup Server List area, in the
Address
field, type the
IP address of the DNS server(s) you want to add.
The system uses these DNS servers to validate DNS lookups and resolve host names. Then,
click
Add
.
If you did not disable DHCP before the first boot of
the system, and if the DHCP server provides the information about your local DNS servers, then
this field is automatically populated.
Click
Update
.
Creating nodes using host names
Determine the fully-qualified domain name (FQDN) that you want to use to identify a
node.
You can create nodes identified by FQDNs and then create a pool and add pool
members from a list of nodes.
On the Main tab, expand
Local Traffic
, and click
Nodes
.
The Node List screen opens.
Click the
Create
button.
The New Node screen opens.
In the
Name
field, type a descriptive label for the
node.
Names are case-sensitive.
For the
Address
setting, select
FQDN
, and then type the host
name in the field.
In the Configuration area, from the
Health Monitors
list, select the way that you want the system to apply monitors to the
node.
The default setting is
Node Default
.
Node Default
Specifies that the system uses the defined default monitors for
nodes. The default monitors are defined on the Default Monitors screen of the BIG-IP Configuration utility.
Node Specific
Specifies that the system monitors this node with the monitors that
you configure in the
Select Monitors
setting.
When you select the
Node
Specific
option, the screen refreshes to display the
Select Monitors
setting.
None
Specifies that the system does not monitor this node.
In the
Ratio
field, type a number for the ratio weight
of the node.
In the
Connection Limit
field, type a number for the
maximum established connection limit for the node.
In the
Connection Rate Limit
field, type a number that
specifies the number of new connections accepted per second for the node.
From the
Address Type
list, select whether the node
resolves to an IPv4 or IPv6 address. The default is
IPv4
.
From the
Auto Populate
list, select
Enabled
. The options are:
Enabled
The system automatically creates ephemeral nodes using the IP
addresses returned by the resolution of a DNS query for the FQDN, that
is, for each DNS entry of the resolved FQDN.
Disabled
The system automatically creates a node that corresponds to the IP
address of only the first DNS entry of the resolved FQDN.
In the
Interval
field, type the number of seconds before
the system creates new ephemeral nodes or deletes expired ephemeral nodes based
on the IP addresses returned in response to a DNS query for the FQDN of the
node. The default is the TTL of the IP address in the DNS response.
In the
Down Interval
field, type the number of seconds
the system waits to mark an FQDN node down following a DNS query failure.
Click
Finished
.
The screen refreshes, and the new node appears in the node
list.
Creating a pool using host names
Before creating a pool, determine the servers that you want to add to the pool using
a fully-qualified domain name (FQDN).
Ensure that your DNS servers return all available IP addresses,
instead of just one IP address.
When you want the BIG-IP system to automatically update pool
members as you make changes to the IP addresses of servers in your network, you can
create a pool of servers that are identified by FQDNs.
On the Main tab, click
Local Traffic
Pools
.
The Pool List screen opens.
Click
Create
.
The New Pool screen opens.
In the
Name
field, type a unique name for the pool.
For the
Health Monitors
setting, from the
Available
list, select a monitor and move the monitor to the
Active
list.
A pool containing nodes represented by FQDNs cannot be monitored by
inband
or
sasp
monitors.
From the
Load Balancing Method
list, select how the system distributes traffic to members of this pool.
The default is
Round Robin
.
In the
New Members
setting, add at least one node with a static IP address. This node serves as a fallback if a DNS query returns no records for the nodes identified by FQDNs.
Select
Node List
.
From the
Address
list, select a node identified by a static IP address.
From the
Service Port
list, make a selection.
Click
Add
.
In the
New Members
setting, add the members that you want to include in the pool using FQDNs.
Select
FQDN Node List
.
From the
Address
list, select a node identified by an FQDN.
Make a selection from the
Service Port
list.
In the
New Members
setting, select
Enabled
. The options are:
Enabled
The system generates an ephemeral node for each IP address returned in response to a DNS query for the FQDN of the node. Additionally, when a DNS response indicates the IP address of an ephemeral node no longer exists, the system deletes the ephemeral node.
Disabled
The system selects the first address and generates an ephemeral for that address.
Click
Add
.
Repeat steps 7-9 to add additional members to the pool.
Click
Finished
.
The screen refreshes, and you see the new pool in the Pool list.
About modifying nodes and pool members identified by host names
When you change the configuration of a fully-qualified domain name (FQDN) pool member or node,
any ephemeral pool members or nodes that the BIG-IP system created based on
the IP addresses returned in a DNS response for that FQDN are automatically modified, as well.
For example, if you change the monitor on an FQDN node, the system automatically changes the
monitor assigned to the ephemeral nodes associated with that node.
When you want to modify an FQDN pool member or node, but you want persistent and active
connections to be completed before the BIG-IP system marks the pool member or node as down,
disable the pool member or node first, and then make modifications.
Task summary
Disabling a node
Determine the node that you want to disable.
You can disable a node when you want to make changes to your network, but you want
persistent and active connections to be completed before the BIG-IP system marks the node as down.
On the Main tab, click
Local Traffic
Nodes
.
The Node List screen opens.
In the Name column, click a node name.
In the State area, click
Disabled (Only persistent or active
connections allowed)
.
You can only disable the parent FQDN node or pool member.
After disabling, the ephemeral dependents are then disabled, but you cannot
directly disable an ephemeral node.
Click
Update
.
The screen refreshes, and the status in the Availability area
changes.
Disabling a pool member
Determine the pool member that you want to disable. You can only disable a parent
fully-qualified domain name (FQDN) node or pool member. The ephemeral dependents are
then disabled. You cannot directly disable the ephemerals.
Disable a pool member when you want to make changes to your network, but you want
persistent and active connections to be completed before the BIG-IP system marks the pool member as down.
On the Main tab, click
Local Traffic
Pools
.
The Pool List screen opens.
Click a pool name in the Pool List.
On the menu bar, click
Members
.
In the
Member
list, select the relevant pool member.
In the State area, click
Disabled (Only persistent or active
connections allowed)
.
Click
Update
.
The screen refreshes, and the status in the Availability area changes.
About pool member and node statistics
You can view statistics about pool members and nodes identified by host names.
Task summary
Viewing statistics for a specific node
Ensure that at least one LTM node exists on the BIG-IP system.
You can view statistics for an LTM node when you want to analyze BIG-IP system
traffic.
On the Main tab, click
Statistics
Module Statistics
Local Traffic
.
The Local Traffic statistics
screen opens.
From the
Statistics Type
list, select
Nodes
.
Information displays about
the node.
Viewing statistics for ephemeral pool members
Ensure that at least one LTM node exists on the BIG-IP system.
When you want to analyze how the BIG-IP system is handling traffic, you can view
statistics for pools and pool members, including the ephemeral pools created when the
pool member is identified by a fully-qualified domain name (FQDN) and
Auto
Populate
is enabled for the pool member.
On the Main tab, click
Statistics
Module Statistics
Local Traffic
.
The Local Traffic statistics
screen opens.
From the
Statistics Type
list, select
Pools
.
Information displays about
the pools configured on the BIG-IP system. The ephemeral pool members are shown
indented below their parent pool member and with two dashes preceding the pool
member name.
