Calayst SDWAN VOIP call preservation - SD WAN

[kbettich1]

A given customer site Catalyst SD-WAN Edge uses an MPLS and an Internet tunnel back to a remote site Catalyst SD-WAN Edge. VOIP calls are preferred over the MPLS tunnel by policy. MPLS circuit goes down at Site 1. VOIP calls fail over to the Internet tunnel. Will calls in progress (i.e. active calls at the time of failover) be preserved or torn down? In other words will voip calls gracefully fail over to the Internet tunnel with maybe just a few seconds dead air without losing the active call or will my active calls be dropped forcing users to place new calls? Do standard BFD timer & multiplier need to be reduced to achieve that goal?

[Torbjørn · Accepted solution]

Hello @kbettich1,

If the failover is caused by losing next-hop/interface going down the failover should be fairly quick. If it is an indirect error you must rely on BFD to declare the tunnel as down, this takes a few seconds and might cause the call to drop. I would probably set this up in a lab to test how the VOIP application handles these failovers and make adjustements accordingly. Note that if you reduce the BFD multiplier or reduce the BFD interval time this might make you more susceptible to excessive flapping.