WAN Redundancy
The ESBC supports 2 redundant WAN ports. Under normal operation, the ESBC will operate using the primary WAN network:

If the primary interface is unavailable, voice traffic will switch to the backup WAN network:

The primary WAN interface is deemed unavailable under the following circumstances:

• Layer 2 link connectivity is lost
• Layer 3 IP address is lost
• The ability to ping a host on the WAN network is lost

If revertive mode is enabled, the ESBC will automatically fail back to the primary WAN interface when it is available. Manual switchover is also possible between interfaces.

The WAN redundancy feature allows configuration of the following parameters:

• Up to 3 ping hosts on each network
• Up/down detection intervals and number of events for both Layer 2 and Layer 3 detection of loss of interface
• Overriding the SIP registration timers both to the SIP server and the LAN SIP UA’s to allow fast failback to the primary WAN network

Even if both WAN links fail, the ESBC offers Hosted Voice Local Survivability, where LAN IP Phones can communicate to each other without a WAN network connection.