If you configure the networks that support your BIG-IQ solution so that
the discovery and listener functions use the same subnet, F5 recommends that you configure
the routing so that the listener and cluster functions use a different network interface.
When you discover a BIG-IP from the BIG-IQ, you can either use the
BIG-IP device's out-of-band eth0 address or you can use one of the device's self IP
addresses. Using the eth0 address for the discovery function is fine, but you want to make
certain that traffic for the listener functions flows over an in-band, self IP address.
When you configure a BIG-IQ or BIG-IP device, you specify whether to use
the management (mgmt) address (eth0) to discover that device or one of the device's self IP
addresses, which always use another network interface. Once you set the discovery address
for a device, the process for changing it, requires that you reconfigure any DCD cluster
setup you have already completed. Consequently, it's best to get this right the first time.
The volume of traffic that the BIG-IP needs to send to the DCD for
statistics/analytics as well as logging events and alerts is referred to as listener
traffic. This listener traffic can overwhelm the BIG-IP device's eth0 interface. To avoid
performance degradation triggered by excessively high traffic levels, F5 recommends that
you route this traffic over one of the device's self-IP addresses. These self IP addresses
use one of the (eth1-3) interfaces instead of the slower eth0 interface. To ensure that the
listener traffic uses one of the higher speed interfaces, you can configure a routing
If you don’t create a route to the DCD listener addresses that prefers
the BIG-IP device's default gateway, it is quite possible that the listener traffic will
use the (10-100 times slower), OOB network.
A simpler way to make sure that traffic for these two functions use a
separate interface and subnet is to add additional subnets.