GTM and IP selection

The job of the GTM is the monitor the LTM and the LTM monitors the application instance. So, in your scenario, are you saying that the application fails, LTM notices, tells the GTM, then the GTM starts handing out the new available site, then the client fails because it never re-requests? If so, getting GTM to hand out the IP address of the broken application won't fix this will it? You application is down and the user's requests would fail anyway.

 

(If you want to do this, you don't need a wideip in GTM, you can just add a host A record) in Zonerunner since it is static, there's nothing dynamic about it. GTM will only hand out IP addresses that it sees as UP if they are defined in a wideip). The only static IP in a wideip would be the Fallback IP. You can select this as a fallback DNS response in the 3rd load balancing method)

 

In versions 9.2.X and later a feature called Route Health Injection was introduced. This allows the BIG-IP to participate in BGP, OSPF, or RIP to pull virtual servers in and out of dynamic routing so that IP address would move over to the second site and be hosted by your LTM's at site B. You'd need to run that same routing protocol on your routers and make sure to have the routing module on your BIG-IP LTM's.

The job of the GTM is the monitor the LTM and the LTM monitors the application instance. So, in your scenario, are you saying that the application fails, LTM notices, tells the GTM, then the GTM starts handing out the new available site, then the client fails because it never re-requests?

 

 

Correct, this is exactly what is happening and I know that the GTM won't hand out the broken IP, that is not my intention. Ideally, I would like to have the IP be the same or move (as you suggested) to the other site, so that we do not have to depend on the client to re-request the IP. Just wasn't sure how to do that with the GTM. Thanks.

You made a statement "We would like the GTM to always hand out the same IP, regardless of which data center is active". Wouldn't that be the definition of a static entry in DNS? If you add a static A record it would do that. I feel like you mean something else.

 

 

Solution 1 (not so great) The GTM can hand out two IP addresses at the same time, but there is no guarantee which one the client uses in which order. That is the problem with handing out two simultaneously.

 

Solution 2 (good) You can combine the GTM with BIG-IP Local Traffic Managers doing Route Health Injection to accomplish a scenario where the IP address moves (via BGP, RIP, OSPF) when all services behind that vip become unavailable. Route Health Injection means that if a service goes away, BIG-IP at site1 withdraws the route for that virtual and your routers in the network will push traffic to the secondary site still pointing at the same IP and the client does not need to re-request. This requires BIG-IP LTM at both sites with routing modules.

 

You made a statement "We would like the GTM to always hand out the same IP, regardless of which data center is active". Wouldn't that be the definition of a static entry in DNS? If you add a static A record it would do that. I feel like you mean something else.

 

 

Solution 1 (not so great) The GTM can hand out two IP addresses at the same time, but there is no guarantee which one the client uses in which order. That is the problem with handing out two simultaneously.

 

Solution 2 (good) You can combine the GTM with BIG-IP Local Traffic Managers doing Route Health Injection to accomplish a scenario where the IP address moves (via BGP, RIP, OSPF) when all services behind that vip become unavailable. Route Health Injection means that if a service goes away, BIG-IP at site1 withdraws the route for that virtual and your routers in the network will push traffic to the secondary site still pointing at the same IP and the client does not need to re-request. This requires BIG-IP LTM at both sites with routing modules.

 

Hi Experts,

 

 

May you please give me a document (or URL) regarding configuration of RHI in BIG-IP? or even a sample configuration?

LTM and GTM use ZebOS for the configuration of advanced routing protocols, Click here for the ZebOS configuration guide.

 

 

Denny

Does RHI require a separate license key? Or is it included in the base license?

You will need a routing module license.

Ta. Thought so.

 

 

When using RHI + BGP to fail the same public vserver VIP between datacenters doesn't this imply that you are failing over at minimum a /24 of address space? I think this is the minimum size subnet most transit providers will allow you to advertise.