ACE Topology

Question

Hi,
I have two ACE 4710 with four gig ports  appliacne in head office and one ACE in the DR site. In head office I am running Active Active Context in Routed Mode. My ACE is doing the routing as well as Load balancing. The Disaster recovery site ACE is stand alone routed mode with one context.
In current situation if ACE one box goes down load balancing will start happening from the ACE two box context two.
But now I wanted add the third ACE which is located in DR in a way that in case of both ACE in head office goes down Load balancing will start working from the DR ACE.
Head office has four gigabit port one for LAN, WAN, Internet and one for the management. I dont have the extra port in head office.
I need the assistance if this is possible then any example or someone configure it in his network.

Answer 1

Fault tolerance configuration in ACE is limited to two physical devices which will be configured in active/standby mode and exchange state, configuration and heart beats via a dedicated Fault Tolerant VLAN. You can configure fault tolerance for virtual contexts seperately, and they do not have to follow the device level active/standby assignment but you are still limited to two physical devices. If this is the configuration you have at the head office, then you will not be able to add a third device regardless of how ports or contexts have been configured.
For fail-over across sites (ie head office and DR site) you should consider a global site loadbalancing solution such as Cisco Global Site Selector (GSS). Using GSS you can monitor for availability of ACE devices at the head-office and in case of failure, trigger a DNS based rule which will direct traffic to the DR site ACE. -George K.