Specifications

TN2602AP IP Media Resource 320
Issue 6 February 2007 269
Virtual IP and MAC addresses to enable bearer duplication
Duplicated TN2602AP circuit packs in a PN share a virtual IP and virtual MAC address. These
virtual addresses are owned by the currently-active TN2602. In addition to the virtual IP
address, each TN2602 has a "real" IP address. All bearer packets sent to a PN that contains
duplicated TN2602AP circuit packs, regardless of whether the packets originate from TN2602s
in other PNs or from IP phones or gateways, are sent to the virtual IP address of the TN2602
pair in that PN. Whichever TN2602AP circuit pack is active is the recipient of those packets.
When failover to the standby TN2602 occurs, a negotiation between TN2602s to determine
which TN2602 is active and which is standby takes place. State-of-health, call state, and
encryption information is shared between TN2602s during this negotiation. The newly-active
TN2602AP circuit pack sends a gratuitous address resolution protocol (ARP) request to ensure
that the LAN infrastructure is updated appropriately with the location of the active TN2602.
Other devices within the LAN will update their old mapping in ARP cache with this new
mapping.
Requirements for bearer duplication
The Communication Manager license file must have entries for each circuit pack, with the
entries having identical voice channels enabled. In addition, both circuit packs must have the
latest firmware that supports bearer duplication.
Duplicated TN2602AP circuit packs must be in the same subnet. In addition, the Ethernet
switch or switches that the circuit packs connect to must also be in the same subnet. This
shared subnet allows the Ethernet switches to use signals from the TN2602AP firmware to
identify the MAC address of the active circuit pack. This identification process provides a
consistent virtual interface for calls.
Combining duplication and load balancing
A single port network can have up to two TN2602AP circuit packs only. As result, the port
network can have either two duplicated TN2602AP circuit packs or two load balancing
TN2602AP circuit packs, but not both a duplicated pair and a load-balancing pair. However, in a
Communication Manager configuration, some port networks can have a duplicated pair of
TN2602AP circuit packs and other port networks can have a load-balancing pair of TN2602AP
circuit packs. Some port networks can also have single or no TN2602AP circuit packs.