DNS-SRV Load Balancing Issue with SAG (Doc ID 2131540.1)

Last updated on NOVEMBER 16, 2023

Applies to:

Symptoms

 Customer has configured a session agent with hostname as an FQDN : abc.india.xyz

session-agent
hostname abc.india.xyz
ip-address
port 0
state enabled
app-protocol SIP
app-type
transport-method UDP
load-balance-dns-query hunt

Below is the list of DNS-SRV records available for routing. Hence when call is routed to this SA (as next-hop), it should go through below interfaces in load-balanced fashion.

SBC# sh dns cache-entry CRE-CORECRE srv:_sip._udp.abc.india.xyz
Query-->
Q:SRV _sip._udp.abc.india.xyz ttl=20631
Answers-->
prio=40 wgt=100 abc1c.india.xyz:5060/UDP
prio=40 wgt=100 abc1b.india.xyz:5060/UDP
prio=40 wgt=100 abc1d.india.xyz:5060/UDP
prio=40 wgt=100 abc1a.india.xyz:5060/UDP
prio=10 wgt=100 abc.america.xyz:5063/UDP
prio=10 wgt=100 abc.america.xyz:5062/UDP
prio=10 wgt=100 abc.america.xyz:5061/UDP
prio=10 wgt=100 abc.america.xyz:5060/UDP

1) If we configure this SA as next hop, load-balancing is working fine.

2) But, if we create a SAG, with this SA as the only destination, in that case, calls always go through the first interface available in the DNS-SRV records. It never uses the other SRV records.

session-group
group-name sag-abc.india.xyz
description
state enabled
app-protocol SIP
strategy Hunt
dest abc.india.xyz

Cause

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