Recommended Network design

TPO cluster use virtual IP addresses in order to achieve hot backup. A virtual IP address is basically not more than a classical IP address moving from one TPO to another in case of TPO failure. The cluster achieve this task automatically however this will also trigger ARP Gratuitous requests on the network from the TPO which takes in charge a failing TPO job. These ARP requests are sent in order to inform the subnet that arp tables are out of date regarding to the virtual IP address.

These ARP gratuitous requests are most of the time dropped by the switching infrastructure as these packets are considered as IP spoofing attempt. IT Team must insure that within the subnet where TPO are defined, ARP gratuitous requests will not be dropped/properly handle.

IPTrade devices handle these ARP request automatically, however some PBX vendor devices may not handle them properly/immediately. That’s why IPTrade strongly recommend that TPO clusters use their own IP subnet with the following benefits:

•Every voice device like PBX phones or Voice gateways will not need to handle ARP gratuitous requests. From these devices perspective, nothing has moved as the TPO subnet gateway ensures the MAC address move on its own. The TPO subnet gateway is a device that MUST accept ARP gratuitous request.

•IT Team will control easily the number of switch ports where ARP Gratuitous requests must not be dropped. IT Team may limit this authorization to the TPO subnet only.

•Turrets devices may or may not be set in the same TPO Cluster subnet (except XMA based turret that will not handle ARP gratuitous). The IT Team may freely set them into any subnet.

•Multiple TPO clusters can coexist inside the same subnet without incidence.