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amritkp789's avatar
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Apr 01, 2019

GTM Sync config Save

Just a basic (may sound Silly as well ) GTM Question regarding Sync - If I have 4 GTMs in a sync grp (GTMA,GTMB, GTMC, GTMD) , none of them have autosave option enabled and I did a latest change on GTMA followed by "save sys config" in TMSH. So, will the rest of the GTMs get the updated bigip_gtm.conf file or do I need to type "save sys config" in TMSH of all the other GTMs ?


4 Replies

  • Hi Lokesh,


    GTM config configuration is centralized in bigip_gtm.conf. this configuration is automaticly sync. For that you just have to a GTM synchronization group (


    When a change is made on one GTM system in the GTM synchronization group, that change is automatically synchronized to the other systems in the group.


    LTM COnfiguration (VS, node, pool, ...) is written to bigip.conf (and is shared configuration as far as LTM HA is concerned - if you have a HA pair, that config will be replicated to the other members of the LTM device-group). This configuration is sync manually or automaticly if you set it.


    Additional information (response from IanB - F5):


    GTM is always active - there's no concept of failover/standby within the product - if it receives a DNS request on a listener, it will respond to it.


    The exception to this is if you have a listener configured on a floating IP address - in this case, only the BigIP which has that floating address will respond to a DNS request directed there.


    Typically each GTM would have a separate listener. The listener is actually an LTM virtual server, and is not part of the GTM configuration, so it is not present in bigip_gtm.conf


    GTM is simply a DNS resolver. The means by which requests are sent to the GTM is beyond the control of the GTM itself - that process is just the normal DNS resolution process whereby the NS records for your domain should point to your GTMs, and the resolver round robins the response.


    In other words, if you have two GTMs, you should also have tow NS entries for the domains that your GTM resolves for. Those NS entries will be configured on the parent zone, and provide resolvers with the IP addresses of the name servers that resolve for that domain. This all happens before the GTM sees the request, so it can not influence this process.


    In most cases, customers have two GTMs. Each has a listener configured in a subnet appropriate to the subnet it is connected to, and both listeners are configured as NS records. Requests are round robined by the normal DNS resolution process between both GTMs. Once either GTM in a sync group receives the query, the answer given will be consistent (ie, both GTMs would provide the same answer, regardless of which one is queried)



    Hope it help you.




  • BIG-IP DNS configuration synchronization is automatic and updates the bigip_gtm.conf file for all members of the synch group. For a detailed set of actions, see solution K13690.


  • That sounds more like how configuration synchronization works in the DSC (Device Service Cluster) model, which is not what BIG-IP DNS uses.


  • The ConfigSync feature synchronizes changes in the running configuration between devices in the same device group through the device service clustering (DSC) architecture.


    When the Automatic Sync feature is enabled for a device group, the BIG-IP system automatically synchronizes configuration changes, but does not save the changes to the configuration files on each device in the device group.


    While this may not be expected, this behavior is by design and recommended for larger configurations to avoid long ConfigSync duration due to large configurations.


    Note: A manual ConfigSync synchronizes changes to the peer devices and saves the running configuration to the configuration files on the peer devices.


    In some cases, you might want to configure the Automatic Sync feature to update the running configuration and save the configuration to the configuration files on each device in the sync group. Depending on your BIG-IP version, you can do this by setting the save-on-auto-sync option to true for the Root trust domain or device group.


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