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Peter_Casey_716's avatar
Peter_Casey_716
Icon for Nimbostratus rankNimbostratus
Aug 13, 2012

F5 Global Traffic Manager

Hi folks,

 

 

I have been asked to look into, and prepare a paper on the implementation of a global load balancing solution for our two data centres, one based in Manchester, UK & the other based in Guildford, UK. At present, we manually configure failover by updating DNS entries, which can take upto 24 hours to propagate to all servers on the Internet.

 

 

When doing research, I have come across the F5 Global Traffic Manager (GTM) product, which at a high level appears to do exactly what we want it to do.

 

 

Unfortunately, the information I can find about the product is limited, it is either really vague, or really technical.

 

 

My understanding of the solution we require so far is:

 

 

- We will have (atleast) one unit in each site

 

 

- These act as the authoratative servers for our domain (3Dns)

 

 

- These communicate internally using iQuery (I assume this is similar to HSRP/VRRP in networking) and should a failure occur in either site, the failed servers are removed from the "virtual site" (there can be upto 10 seconds of downtime for some users due to caching)

 

 

 

Unfortunately i'm still unable to get my head around the DNS aspect, and also have the following questions:

 

 

- is replication between devices stateful, i.e if there is a failover during active connections, will these continue to be served or will they time-out?

 

 

- what happens should the internal heartbeat be lost between devices but the upstream Internet connections continue to function fine, can the device communicate using a VPN-style public connection?

 

 

Any info that can be given would be greatly received.

 

 

Best regards,

 

 

Peter

 

config
design

4 Replies

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  • Laudec_55181's avatar
    Laudec_55181
    Icon for Altostratus rankAltostratus
    Aug 13, 2012
    Hi Peter,

     

     

    Global Traffic Manager will definately help you to provide high availability between your datacenters. Most of your points are correct, but here are some corrections:

     

     

    - Yes, you need at least one GTM per site. They will run as standalone devices, but will be configured in a sync group that will enable them to work together for resolution.

     

    - iQuery is an F5 Networks, UDP-based protocol that collects configuration and metric information and exchanges that information between 3-DNS Controllers and other F5 Networks products running the big3d agent.

     

    - iQuery replicates any configuration changes between the GTMs. But, each device keeps its own copy of the configuration. GTM only does DNS resolution, although in a much more intelligent way than standard BIND does. If a failover happens, new DNS queries will be resolved to alternate addresses.

     

    - if the internal heart beat is lost, the boxes will assume the other site is down, and not give out address resolutions for that site. Could be an issue if you run an active/ cold standby datacenter scenario. Not so much an issue, if it is a hot standby site.

     

     

  • Peter_Casey_716's avatar
    Peter_Casey_716
    Icon for Nimbostratus rankNimbostratus
    Aug 13, 2012
    Hi there,

     

     

    Thanks for the response.

     

     

    Ok, so should we push on with the purchase of two of these units (one for each site), get them synced up, can you explain how the DNS would work? Clients would access www.website.co.uk which would then resolve to what? Do these devices share a common (virtual) IP address?
  • Cory_50405's avatar
    Cory_50405
    Icon for Noctilucent rankNoctilucent
    Aug 13, 2012
    These GTMs would just act as your authoritative DNS servers. They would hand out the DNS answers that you configure them to hand out. Each GTM will be configured with a different public IP address and you would register the GTM IP addresses as the authoritative name servers for your domain. They will not share any VIPs between the two units, but will be configured to hand out the same answers since they will share their configurations with each other.
  • Hamish's avatar
    Hamish
    Icon for Cirrocumulus rankCirrocumulus
    Aug 13, 2012
    I prefer to deploy GTM's as authoritative for a SEPARATE domain... e.g. dynamic.domian.com not domain.com. Then to implement a GTM hosted address, get everything all setup and tested as site.dynamic.domain.com and simply flip site.domain.com from a A record to a CNAME site.dynamic.domain.com

     

     

    Best of all worlds then... GTM only services GTM addresses. Easy test and fallback. etc etc.

     

     

    Oh... GTM doesn't need to even be at your site. It simply needs to be able to monitor the devices providing the balanced services. A minimum of two should however be provided of course.

     

     

    H