Maintaining the Device Service Cluster (DSC)
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In this section we will review the things you may encounter while administering a Device Service Cluster (DSC) when administering high availabilty on the BIG-IP.

Let's first take a look the status of our HA pair.  You can find the status at anytime in the upper left corner of the TMUI interface next to the big red F5 ball.  Here you will see the current redundancy state, whether the BIG-IP is an **ACTIVE** state (processing application traffic) or a **STANDBY** (no configurations items are processing traffic) and the current configsync status.  Our BIG-IP is a standard Active-Standby pair, the most common HA configuration.

Open the TMUI interfaces for **bigip01** and **bigip02** and observe the state of the DSC.  

.. WARNING::
    You should always check the redundancy state before making any configuration changes on the BIG-IP.  By default any BIG-IP can be the active device. For purposes of the lab environment the failover configuration has been modified to make **bigip01** the active device whenever it is up and enabled.

Your current state and status on **bigip01** should be **ACTIVE** with **Changes Pending** since you have been modifying the configuration throughout the labs.  

Your current state and status on **bigip02** should be **STANDBY** with **Changes Pending** since you have been modifying the configuration throughout the labs.  

On **bigip01** go to **Device Management >> Device** and click on the **bigip01.f5demo.com (Self)** link.

This will give you access to HA settings, such as, IP configsync listens for updates on, etc.  Also from here your can force the BIG-IP to failover by selecting **Force to Standby** or **Force Offline**.

.. image:: /_static/201L/ha-redun-online.png

On **bigip01** go to **Device Management >> Traffic Groups** on each BIG-IP.  There you will find a list of the configured traffic groups and what the next active device is.  Here you can force a particular traffic group to failover.  Clicking on a traffic group gives you more detail and configuration options.

.. image:: /_static/201L/ha-traffic-group.png

On **bigip01** click on **Changes Pending** or go to **Device Management >> Overview**.  Here you can see the last time the DSC was in sync.  You can see the configuration time for each device in the cluster.  Here you have the option to push or pull the configuration.  

.. image:: /_static/201L/ha-overview.png

.. NOTE::
    The red status of **bigip02** is do to the nature of the lab environment and the DSC being brought up all of a sudden causes the configuration timestamps to be off

Since you can been making changes to **bigip01** you can sync the configurations by selecting **bigip01**, selecting **Push** and hitting the sync button.  This pushes the configuration the other devices in the cluster.  Do that now.

Alternately, you could have go to **bigip02** and done a pull, by selecting **bigip02** and selecting the **Pull** option.  This would pull the configuraton from another device in the cluster and overwrite the configuration of **bigip02**.

.. image:: /_static/201L/ha-pull.png

This is an important distinction.  Consider a scenario where you are making changes to the Active BIG-IP and you delete configuration or make a configuration error that causes traffic to be lost.  On way to recover would be to do a restore from an archive, but that is not a quick process.

You could instead, failover the Active BIG-IP with the errors, now traffic is being processed again. Then on the misconfigured BIG-IP you could to a configsync pull and recover the configuration.