F5 BIG-IP Global Traffic Manager (GTM) provides tiered global server load balancing (GSLB). BIG-IP GTM distributes DNS name resolution requests, first to the best available pool in a wide IP, and then to the best available virtual server within that pool. GTM selects the best available resource using either a static or a dynamic load balancing method. Using a static load balancing method, BIG-IP GTM selects a resource based on a pre-defined pattern. Using a dynamic load balancing method, BIG-IP GTM selects a resource based on current performance metrics collected by the big3d agents running in each data center.

So F5 GSLB configuration logic for a DNS record is as below:

• Define a Data Center, e.g. “SL-SYD-Site1”;
• Define a server which can be F5 LTM or any other kind of local load balancer or host;

• Create virtual servers if you don’t use F5 BigIP LTM or you don’t “Virtual Server Discovery” feature for your F5 BigIP LTM
• Create GTM pool/pools using virtual server as member of this newly created pool;
• Create Wide-IP which points to the GTM pool/pools which you defined in the previous step ; Note: F5 module in Ansible 2.3 still doesn’t support the association of GTM pool with wide-ip.

Unlike F5 BigIP LTM, Ansible F5 module doesn’t support F5 BigIP GTM very well. The known limitation of automating F5 GSLB configuration with Ansible version 2.3 includes:

1. Doesn’t support setting up a server; (Luckily, if you are using F5 BigIP LTM, this is one-off task: you only need to perform this task once for each LTM.)
2. Doesn’t support adding pool member when you create a GTM pool;
3. Doesn’t support adding pool when you create a wide ip;
4. Doesn’t support health monitor when you create GTM virtual server and GTM pool;

To accommodate these above limitation, I pre-defined a F5 LTM server called “myLTM”. 

After running my Ansible playbook, I manually add pool member into newly created GTM pool and add the GTM pool to wideip as well.

My playbook YAML file:

– name: f5 config
hosts: lb.davidwzhang.com
connection: local
tasks:
– name: create a GTM DC SL-SYD-Site1
bigip_gtm_datacenter:
password: “password”
server: “10.1.1.122”
user: “admin”
name: “SL-SYD-Site1”
validate_certs: “no”
delegate_to: localhost
– name: create a virtual server myVIP
bigip_gtm_virtual_server:
password: “password”
server: “10.1.1.122”
user: “admin”
virtual_server_name: “myVIP”
virtual_server_server: “myLTM”
validate_certs: “no”
port: “80”
address: “192.168.72.199”
state: “present”
delegate_to: localhost

– name: create GTM pool: mypool
bigip_gtm_pool:
server: “10.1.1.122”
user: “admin”
password: “password”
name: “mypool”
state: “present”
type: “a”
validate_certs: “no”
delegate_to: localhost

– name: create a wideip w3.davidwzhang.com
bigip_gtm_wide_ip:
server: “10.1.1.122”
user: “admin”
password: “password”
lb_method: “round_robin”
name: “w3.davidwzhang.com”
type: “a”
state: “present”
validate_certs: “no”
delegate_to: localhost

Ansible Playbook Output:

GTM DC

GTM Virtual Server

GTM Pool

GTM WideIP

NSlookup for wideip: w3.davidwzhang.com

Ansible has included F5 as extra network module, which can help to provide LBaaS by use of Infrastructure as Code method.

Like normal Ansible modules,  Ansible F5 module is installed the /usr/lib/python2.7/site-packages/ansible/modules/extras/network directory.

[dzhang@localhost network]$ pwd
/usr/lib/python2.7/site-packages/ansible/modules/extras/network
[dzhang@localhost network]$ ls -al
total 512
drwxr-xr-x. 9 root root 4096 Jan 30 03:17 .
drwxr-xr-x. 20 root root 4096 Jan 30 03:17 ..
drwxr-xr-x. 2 root root 4096 Jan 30 03:17 a10
drwxr-xr-x. 2 root root 4096 Jan 30 03:17 asa
drwxr-xr-x. 2 root root 4096 Jan 30 03:17 citrix
-rw-r–r–. 1 root root 24673 Jan 16 08:48 cloudflare_dns.py
-rw-r–r–. 2 root root 18915 Jan 16 14:36 cloudflare_dns.pyc
-rw-r–r–. 2 root root 18915 Jan 16 14:36 cloudflare_dns.pyo
-rw-r–r–. 1 root root 11833 Jan 16 08:48 dnsimple.py
-rw-r–r–. 2 root root 8642 Jan 16 14:36 dnsimple.pyc
-rw-r–r–. 2 root root 8642 Jan 16 14:36 dnsimple.pyo
-rw-r–r–. 1 root root 13723 Jan 16 08:48 dnsmadeeasy.py
-rw-r–r–. 2 root root 12410 Jan 16 14:36 dnsmadeeasy.pyc
-rw-r–r–. 2 root root 12410 Jan 16 14:36 dnsmadeeasy.pyo
drwxr-xr-x. 2 root root 4096 Jan 30 03:17 exoscale
drwxr-xr-x. 2 root root 4096 Jan 30 03:17 f5
-rw-r–r–. 1 root root 13404 Jan 16 08:48 haproxy.py
-rw-r–r–. 2 root root 13504 Jan 16 14:36 haproxy.pyc
-rw-r–r–. 2 root root 13504 Jan 16 14:36 haproxy.pyo

The Ansible playbook below is to:

• Create 2 web servers as F5 LTM nodes;
• Create a F5 LTM pool;
• Add the 2 web servers as the member for F5 LTM pool which is created in Step 2;
• Create a F5 LTM vIP and associate the F5 LTM pool created in Step 2 with this newly created vIP;

[dzhang@localhost f5]$ cat f5-v0.4.yml
—
– name: f5 config
hosts: lb.davidwzhang.com
connection: local

tasks:
– name: create a pool
bigip_pool:
lb_method: “ratio_member”
name: “web”
password: “password”
server: “10.1.1.122”
user: “admin”
validate_certs: “no”
monitors:
– /Common/http
delegate_to: localhost
– name: create a node1
bigip_node:
host: “192.168.72.168”
name: “node-1”
password: “password”
server: “10.1.1.122”
user: “admin”
monitors:
– /Common/icmp
validate_certs: “no”
delegate_to: localhost
– name: create a node2
bigip_node:
host: “192.168.72.128”
name: “node-2”
password: “password”
server: “10.1.1.122”
user: “admin”
monitors:
– /Common/icmp
validate_certs: “no”
delegate_to: localhost
– name: add a node to pool
bigip_pool_member:
description: “webservers”
host: “{{item.host}}”
name: “{{item.name}}”
password: “password”
pool: “web”
port: “80”
connection_limit: “0”
monitor_state: “enabled”
server: “10.1.1.122”
user: “admin”
validate_certs: “no”
delegate_to: localhost
with_items:
– host: “192.168.72.168”
name: “node-1”
– host: “192.168.72.128”
name: “node-2”
– name: create a VIP
bigip_virtual_server:
description: “ansible-vip”
destination: “192.168.72.199”
name: “ansible-vip”
pool: “web”
port: “80”
snat: “Automap”
password: “password”
server: “10.1.1.122”
user: “admin”
all_profiles:
– “http”
validate_certs: “no”
delegate_to: localhost

Run the playbook:

[dzhang@localhost f5]$ ansible-playbook f5-v0.4.yml
/usr/lib64/python2.7/site-packages/cffi/model.py:525: UserWarning: ‘point_conversion_form_t’ has no values explicitly defined; guessing that it is equivalent to ‘unsigned int’
% self._get_c_name())

PLAY [f5 config] ***************************************************************

TASK [setup] *******************************************************************
ok: [lb.davidwzhang.com]

TASK [create a pool] ***********************************************************
ok: [lb.davidwzhang.com -> localhost]

TASK [create a node1] **********************************************************
ok: [lb.davidwzhang.com -> localhost]

TASK [create a node2] **********************************************************
ok: [lb.davidwzhang.com -> localhost]

TASK [add a node to pool] ******************************************************
ok: [lb.davidwzhang.com -> localhost] => (item={u’host’: u’192.168.72.168′, u’name’: u’node-1′})
ok: [lb.davidwzhang.com -> localhost] => (item={u’host’: u’192.168.72.128′, u’name’: u’node-2′})

TASK [create a VIP] ************************************************************
ok: [lb.davidwzhang.com -> localhost]

PLAY RECAP *********************************************************************
lb.davidwzhang.com : ok=6 changed=0 unreachable=0 failed=0

In F5 LTM, you can verify the configuration:

LTM Node:

LTM Pool

LTM vIP