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Telnyx SIP connections automatically retry failed call attempts through different routes and IP addresses.

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Signaling IP addresses

Telnyx uses two geographically redundant signaling IPs per region:
RegionPrimary (IP1)Secondary (IP2)
US192.76.120.1064.16.250.10
EU5.172.39.105.172.39.25
Canada193.108.220.10193.108.220.25
Australia103.135.104.10103.135.104.25

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Failover behavior

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Single route

  1. SIP INVITE sent from IP1
  2. On failure, retry from IP2

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Multiple routes

  1. Attempt all routes via IP1 in configured order
  2. On failure, retry all routes via IP2
Route order depends on configured preference (Sequential or Round Robin).

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Credential authentication

Calls route through the registered KSS instance with three levels of internal failover.

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Call forward on failure

When enabled, calls that fail on all SIP routes forward to PSTN (up to 10 termination carriers).

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Response codes

Triggers failover:
CodeMeaning
408Request Timeout
480Temporarily Unavailable
503Service Unavailable
504Server Timeout
Transport errorNetwork/TCP failure
Does NOT trigger failover (call considered connected):
CodeMeaning
180Ringing
200OK (answered)
404Not Found
486Busy Here
603Decline

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DNS configuration

SRV records (recommended): 
_sip._udp.example.com. 3600 IN SRV 10 10 5060 sip.telnyx.com.
Regional domains: sip.telnyx.com (US), sip-eu.telnyx.com (EU) SRV records automatically resolve to both IP1 and IP2. A records (alternative): Configure separate A records for each signaling IP and add both as routes.

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Configuration

PATCH /v2/ip_connections/: 
{
  "default_routing_method": "sequential",
  "call_forwarding": {
    "forwarding_type": "on_failure"
  }
}