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DNS SRV (Service) records enable automatic failover and load distribution for SIP connections by resolving to multiple Telnyx signaling IPs with priority and weight parameters.

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SRV record format

Telnyx SRV records follow RFC 2782 DNS SRV specification: 
_service._protocol.domain TTL class SRV priority weight port target
Example: 
_sip._udp.example.com. 3600 IN SRV 10 10 5060 sip.telnyx.com.

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Parameters

ParameterValueDescription
Service_sipSIP service identifier
Protocol_udp or _tcpTransport protocol (UDP recommended)
DomainUser’s domainThe domain being configured
TTL3600Cache duration in seconds
ClassINInternet class (standard)
Priority10Lower values preferred (use same value for all Telnyx entries)
Weight10Load distribution ratio (equal weight for balanced distribution)
Port5060 or 50615060 for UDP/TCP, 5061 for TLS
Targetsip.telnyx.com.Telnyx regional FQDN (note trailing dot)

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Regional FQDNs

Configure SRV records to point to the Telnyx region closest to the user’s infrastructure:
RegionFQDNResolves to IPs
USsip.telnyx.com192.76.120.10, 64.16.250.10
Europesip-eu.telnyx.com5.172.39.10, 5.172.39.25
Canadasip-ca.telnyx.com193.108.220.10, 193.108.220.25
Australiasip-au.telnyx.com193.108.104.10, 193.108.104.25
For the most current IP addresses and additional regions, see sip.telnyx.com.

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Configuration examples

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Basic configuration

Single SRV record pointing to US region: 
_sip._udp.example.com. 3600 IN SRV 10 10 5060 sip.telnyx.com.

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TLS transport

For encrypted SIP signaling on port 5061: 
_sip._tcp.example.com. 3600 IN SRV 10 10 5061 sip.telnyx.com.

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Multi-region redundancy

Route to US as primary, EU as secondary: 
_sip._udp.example.com. 3600 IN SRV 10 50 5060 sip.telnyx.com.
_sip._udp.example.com. 3600 IN SRV 20 50 5060 sip-eu.telnyx.com.
Priority 10 (US) is preferred over priority 20 (EU).

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Benefits over A records

FeatureSRV RecordsA Records
Automatic IP failoverYes (resolves to multiple IPs)No (manual configuration required)
Port specificationIncluded in recordHardcoded in PBX config
Load balancingWeight-based distributionRequires DNS round-robin
Protocol awarenessTransport specified in recordAssumed by application
Regional routingFQDN-basedIP-based

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Verification

Verify the user’s SRV record configuration: 
dig _sip._udp.example.com SRV
Expected output shows multiple A records for the target FQDN: 
_sip._udp.example.com. 3600 IN SRV 10 10 5060 sip.telnyx.com.

;; ADDITIONAL SECTION:
sip.telnyx.com. 300 IN A 192.76.120.10
sip.telnyx.com. 300 IN A 64.16.250.10
Test resolution to IP addresses: 
dig sip.telnyx.com A

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DNS provider configuration

Most DNS providers support SRV records through their control panel or API. Common DNS providers:
  • Route 53 (AWS): Record type “SRV”, value format 10 10 5060 sip.telnyx.com
  • Cloudflare: Record type “SRV”, configure service, protocol, priority, weight, port, target separately
  • Google Cloud DNS: Use gcloud dns record-sets create with --type=SRV
API example (AWS Route 53): 
{
  "Name": "_sip._udp.example.com",
  "Type": "SRV",
  "TTL": 3600,
  "ResourceRecords": [
    {
      "Value": "10 10 5060 sip.telnyx.com."
    }
  ]
}

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Failover behavior

SRV records work with Telnyx automatic failover:
  1. DNS query resolves sip.telnyx.com to both IP1 and IP2
  2. SIP INVITE sent to IP1 (primary)
  3. On timeout or error, retry to IP2 (secondary)
  4. If all IPs fail, attempt next priority SRV target (if configured)
See Failover and Retries for complete failover logic.

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Troubleshooting

SRV record not resolving:
  • Verify trailing dot on target FQDN (sip.telnyx.com.)
  • Check TTL has expired if you recently updated
  • Confirm DNS propagation: dig @8.8.8.8 _sip._udp.example.com SRV
PBX not using SRV record:
  • Some PBX systems require explicit SRV lookup enablement
  • Configure PBX to use domain (example.com) not IP address
  • Check PBX logs for DNS query behavior
Unbalanced load distribution:
  • Verify equal weight values for balanced distribution
  • Some SIP stacks cache first resolved IP
  • Consider implementing client-side round-robin