DNS GSLB Link object support

[scoffeyfv]

BIG-IP DNS supports "GSLB Link" objects. These provide a means to define 'links' (monitored network paths, commonly internet uplinks) associating next hop router addresses with data centers.

TMSH documentation: https://clouddocs.f5.com/cli/tmsh-reference/v16/modules/gtm/gtm_link.html

https://my.f5.com/manage/s/article/K6848

At present, AS3 does not support management of Link objects.

As a workaround, the Link object can be created manually in the GSLB configuration and associated with a data center. However this then introduces a dependency between this object and AS3 managed data center objects, preventing AS3 from deleting referenced data centers.

GSLB Use Case for Link Objects A frequent requirement for internet facing GSLB deployments is load balancing decisions with awareness of the health of the LTM internet uplink. This can be achieved by routing the iQuery connections from DNS to LTM devices via the internet, however this is sub-obtimal from a security perspective and also requires NAT of the iQuery flow, with implications for Virtual Server Discovery.

The GSLB Link feature enabling monitoring of uplinks from nominated LTM/DNS instances per datacenter, and reflecting that status in the health of virtual servers associated with that datacenter. The iQuery connection can then be routed over private networks between sites without NAT.

Link Object Attribute support The Link object supports many attributes, some of which are primarily associated with the EOL 'Link Controller' product (e.g. those associated with link cost). It also supports configuration of any monitor to be utilised for monitoring the uplink, beyond the "bigip_link" monitor which utilises iQuery for probes (which AS3 could assume as a default). If implementation of these attributes adds complexity, a limited implementation creating an object with only the default bigip_link monitor, and an array of router addresses, would enable the above use case.