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Shane_Terrick_9's avatar
Shane_Terrick_9
Icon for Nimbostratus rankNimbostratus
Dec 16, 2013

Load Balancing WIP across LTMs at 2 datacenters

I am trying to load balance a WIP(app.company.com) across two LTMs across 2 data centers. This is to allow for DR/failover without any manual intervention. So I built out my VIPs on the 2 LTMs,then on the GTM, I built a pool under the WIP which included the 2 VIPs(one at each datacenter). Now my issue is, it seems to only be load balancing on the one VIP and not both.

 

Global TRaffic>>Pools:Pools LIst>>WIP_POOL Members app_prd (at datacenter 1) app_prd_dr (at datacenter 2)

 

All traffic seems to be sent to the app_prd VIP at datacenter 1

 

The only thing that I can come up with is that the DNS record created for the WIP(app.company.com) points to the IP address of the VIP at datacenter 1. If this is the case, what IP should I be using since the WIP doesn't truely have an IP?

 

How there is enough information here. Thanks.

 

design

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  • Christian_30338's avatar
    Christian_30338
    Historic F5 Account
    Dec 16, 2013

    There are a number of reasons why GTM might be sending traffic to one VIP only. To start with have you confirmed that both LTM VIPS status is OK and the reported status in GTM is also OK? Also do you have a Listener configured on GTM? This is where the DNS requests for app.company.com should be coming into. Have a look at this link which talks about GTM Listeners.

     

  • Shane_Terrick_9's avatar
    Shane_Terrick_9
    Icon for Nimbostratus rankNimbostratus
    Dec 16, 2013

    All VIPs status' are ok on the GTM

     

    The only Listener I have created is the self-ip of the GTM

     

    Should i have had my DNS team create the Network DNS records for the app.company.com address to point to this listener IP address instead of the VIPs IP address?

     

    • Jason_40733's avatar
      Jason_40733
      Icon for Cirrocumulus rankCirrocumulus
      Dec 16, 2013
      It sounds like your DNS team is still handling DNS for the domain "company.com". We created a sub-domain "gtm.company.com" and had our normal DNS point to our GTM listeners for any DNS requests for the "gtm.company.com" domain. With that in place, we create entries like "app.company.com" in our normal DNS as a CNAME for "app.gtm.company.com". This gets the DNS request to our GTM and our GTM load balances appropriately ( Remember to set your DNS TTL to your needs ).
    • Shane_Terrick_9's avatar
      Shane_Terrick_9
      Icon for Nimbostratus rankNimbostratus
      Dec 16, 2013
      Correct when we add an address to the GTM such as app.company.com we have our DNS create a record and have been having them point these records to the VIP ip address but it sounds like we should be having them point it to the GTM listener. Am I heading down the correct path? Sorry in advance for the possibility of these questions be very open ended but I am just trying to get more into the use of the GTM and using it correctly and my DNS understanding is lacking a little. Thanks.
    • Jason_40733's avatar
      Jason_40733
      Icon for Cirrocumulus rankCirrocumulus
      Dec 17, 2013
      What we do is the following: We have our existing DNS refer any DNS requests for the gtm.company.com domain to the GTM Listener. If we want app1.company.com to be load balanced using the GTM we make a DNS entry in our main DNS tool called app1.company.com that is a CNAME for app1.gtm.company.com. A client resolving app1.company.com will get referred to app1.gtm.company.com which would then follow the DNS delegation and be requested from the GTM listener. The GTM will send a response with the IP of one of the LTM VIPs depending on the particular load balancing rules for that WideIP ( e.g. app1.gtm.company.com might return 10.10.10.11 or 10.20.10.11 which would be VIPs that can be on the same or different LTMs ). So the GTM itself has no VIP and all DNS queries that are to be load balanced by the GTM are referred to the GTM's listener. The GTM then responds with the IP address of an LTM VIP. If you have the GTM and the LTM modules ( they are separately licensed and provisioned ) running on the same physical Bigip it can be a bit confusing. Key parts of this. The GTM only works by answering DNS queries. It doesn't actually have VIPs. The GTM's listeners are where DNS queries should always be referred to. If you have your existing DNS infrastructure in front of the GTMs and it returns the IP addresses of VIPs for a DNS query, then you are not making use of the GTM. The existing DNS infrastructure must delegate the answer for GTM load balanced DNS queries to the GTM listener. I know I'm repeating myself, but I'm low on coffee. I hope this helps. Jason