More on GTM + LTM design across 2 DC
Hi, hope friends here can share their thoughts. I searched similar topic on this forum and found this one: http://devcentral.f5.com/Community/GroupDetails/tabid/1082223/asg/52/aft/16692/showtab/groupforums/Default.aspx3786.
Now I need a little expansion from that previous topic.
Here is what we have:
1. Two GTM machines in active-standby in DC
2. Two GTM machines in active-standby in DRC
3. Two LTM machines in active-standby in DC
4. Two LTM machines in active-standby in DRC
5. Three ISP in DC and in DRC, lets say ISP A, B and C.
6. A redundant application server that can only be active in one site, either DC or DRC. When it is up in DC, the server in DRC should go off, and vice versa.
7. The traffic flow is incoming, the user is accessing this servers
Here is what they need:
1. GTM to offload NS resolution
2. LTM to front end the app server
3. GTM and LTM should be able to accomodate the A record resolution using those three ISPs (round robin)
4. (If possible) In the event when app server in DC active, then the monitor in LTM reports as active to GTM. Both GTM DC and DRC communicates with each other, so every DNS request coming to either DC or DRC, will resolve the wide IP to DC resources. In opposite, when the app server in DC is shut down purposefully, LTM in DC monitors it as off, reports it to GTM in DC. GTM in DC updates the GTM in DRC, so every request will get the wide IP resolution from GTM and LTM in DRC.
Here is what I will do to cover 1,2,3:
1. Set up three VS in LTM. VS for ISP A, ISP B and C. Each VS has the address from each ISP's segment. Pool member for those three VSs is the same, which is the app server.
2. Set up the LTM interfaces to have (sub)interfaces for each ISP as the way to communicate with the ISP router.
3. Set up a wide IP in GTM that has the pool member: VS IP ISP A, VS IP ISP B, VS IP ISP C.
Now to cover requirement number 4:
1. I searched about iQuery (as a way between GTM and LTM to communicate, and also for GTM in DC and in DRC to communicate) but limited documentation on how to implement it to my topology.
2. I am thinking about :
a. modifying the pool member GTM in DC to: VS IP ISP A, B, C, VS IP ISP A (DRC), ISP B (DRC), ISP C (DRC), classify the ISPs in DC in one class, and ISPs in DRC in another class, and make GTM to choose only the DC class if the server is active in DC and DRC class if the server is active in DRC (not sure how to do this) and vice versa in GTM in DRC.
b. Finding a way for GTM to answer NS resolution accordingly. So when server is active in DC, even though a request comes to GTM in DRC, it will tell the requestor that the NS is now on GTM in DC, go ask that person in DC. (so not sure about this)
Hope I could get some answer here