High availability links are down on Session Border Controller, this leads to both systems becoming active.

Asset ID:	1-71-1919734.1
Update Date:	2017-06-07
Keywords:

Solution Type Technical Instruction Sure

Solution 1919734.1 : High availability links are down on Session Border Controller, this leads to both systems becoming active.

Applies to:

Acme Packet 3820 - Version S-Cx6.0.x and later
Information in this document applies to any platform.

Goal

If Wancom 1 and 2 link are down (geo redundant setup). Which system is active? What utility-address is used?

Solution

Would end up with 'split-brain', both systems in the pair see them as active and the other is not responding. Each would use the virtual MAC and the virtual IP address. This leads to calls being able to route to both SBC's at the same time. When the pair is in this state, a lot of other problems, call failures and so forth can occur. May be recommended to shut one system down in the pair so only one SBC is responding.

Another approach is to also set up the media-if-peercheck-time in the redundancy configuration. By enabling this, before any SBC is considering timed-out, an ARP ping is sent from the standby SBC media interface to the active media interface. You would set the timeout setting in the redundancy-config . If the systems receives arp replies in the time limit, the standby takes itself out of service to prevent conflict with the active. If it does not receive a response in time, it assumes the active system is down and takes control. More information on this can be found in the ACLI Configuration Reference Guide. (search for "HA Media Interface Keepalive") Note, that by default the timer is set to 0, which disables the function.

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