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Application Delivery (ADX)

Posts: 0

Anycast for DNS and GSLB for SMTP?


There are two services to be load balanced:


High availability at site level is also required for both services. We are opting for two models as mentioned below:

- Anycast using RHI for DNS

Anycast using RHI for DNS

DNS service is hosted at four Data Centers and SI is also present at all locations. I am clear about its working and concepts but need some clarification for the following:

- DSR topology is best for Anycast?
- What should be the IP used for management of real servers? I read somewhere that the IP address of physical interface should be the management IP and the service IP should be configured as loopback on real server.
- DSR dictates that the SI and real servers should be on the same L2 domain. Suppose is the Service VIP and needs to be advertised from two locations. Servers will have configured as loopback address. But the physical interface IP should be unique so as to ensure real server reachability to the internet. Can we make the real servers and SI part of IP subnet serving the VIP of


SMTP service is hosted at two Data Centers. We will use GSLB for load balancing between the sites. The model is clear to me but I have two questions:

1- Site ServerIron and Controller should be two separate boxes? Is it possible to configure one of the site load balancers as GSLB controller?
2- Does enabling GSLB (either controller or site LB) adds some restrictions on ServerIron? We will be using the same boxes as part of Anycast DNS plan. I need to be sure that enabling GSLB will not restrict any feature on ServerIron.



Posts: 70
Registered: ‎03-14-2009

Re: Anycast for DNS and GSLB for SMTP?

Hallo Owais,

yes, you can configure the controller and site function on the same box.

currently i am not aware of any feature limitation when using GSLB.



Posts: 0

Re: Anycast for DNS and GSLB for SMTP?

Thanks Alexander.

Can you help answer my Anycast questions as well.


Posts: 0

Re: Anycast for DNS and GSLB for SMTP?

Ho Owais,

DSR- Overview

Direct Server Return (DSR) enables the return traffic to not be processed by the ServerIron ADX. Instead, the real server directly sends the return traffic to the client. In this case, the ServerIron ADX changes the way it sends health checks to the application so that the health checks do not rely

on the return traffic.

SwitchBack configurations enhance server response time and increase capacity on the ServerIron ADX, by allowing server responses to bypass the ServerIron ADX on the way to clients and at the same time increasing the number of simultaneous connections the ServerIron ADX can support.

Its main (but not only) reason is to still increase server responce AND reduce resources used in the SI.

You cannot have a router hop between the ServerIron ADXs. They must have Layer 2 connectivity. So you are correct in that they must connected in the same layer 2 domain.

As for IP address you will need something like assigned so the SI can have 1 address and the Real the other (and yes add the SI ip address as a lookback for the real server).

I hope that helps.



Posts: 0

Re: Anycast for DNS and GSLB for SMTP?

Hi Micheal,

Thank you.

It means that we can have SI Service IP and the real servers and SI interface is part of Servers will have loopback of address will be used by real servers for management and interaction with internet???



Posts: 0

Re: Anycast for DNS and GSLB for SMTP?

temp.jpgYes that is correct .

VIP has public IP address (and that is the address you add as a loopback on the server.

SI interface and real have a address in the same subnet range.

see pic above

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