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Overview

As part of SBC switch-over process, the SBC must move the IP (floating IP) to a different NIC. The SBC reconfigures the NICs appropriately and then broadcasts a GARP reply to inform neighboring devices about the change in the MAC address for the floating IP. Devices that receive the ARP packet then update their ARP tables with the new MAC address.

There is a minor difference between Sonus' SBC SWe and hardware-based SBCs. For the case of hardware-based SBCs during a switchover, both the IP and MAC addresses of the active node's non-management interfaces are migrated to the standby. For SBC SWe during a switchover, only the IP address is migrated from active to standby (the newly active node will use its own MAC addresses).

In both cases, the L2 tables of attached switches are updated; however in the case of SBC SWe, the routers' ARP tables must be updated as well.

ARP cache entries on the router are cleared periodically, typically every 10-20 minutes.  As a result, the ARP table on the router gets updated. At this point, the active CE starts receiving traffic.

Configuring Routers in SBC SWe Network

If a router in an SBC SWe network is not configured properly to handle Gratuitous Address Resolution Protocol (GARP) replies, calls will fail after an SBC SWe switch-over.

For example, the received Gratuitous ARP reply on a Juniper SRX device does not update the ARP cache by default. You must configure the router to enable ARP table update for switch-over to work properly.

A knowledge base article on how to enable the updating of the ARP cache for received gratuitous ARP replies is located here:

http://kb.juniper.net/InfoCenter/index?page=content&id=KB24349

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