Source note · SIP call forwarding and routing loops

RFC 3261 gives proxies an optional loop-detection check that inspects Via header values (sent-by plus branch parameter) and, on detecting a loop, responds 482 (Loop Detected).

Checked 2026-09-25

Vendor: IETF
Product: SIP
Subsystem: proxy loop detection
Deployment: any
Region: not restricted
Release range: RFC 3261 (June 2002); strengthened for forking proxies by RFC 5393
Checked: 2026-09-25

Sources

RFC 3261 — SIP: Session Initiation Protocol — IETF / RFC Editor · tier 1 standards and regulators · Section 16.3 Request Validation, item 4 (Optional Loop Detection check); Section 21.4.20 482 Loop Detected

Cite this note

APA

WarmTransfer. (2026, September 25). SIP call forwarding and routing loops: source note sip-forwarding-loops-482-via-loop-check. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-forwarding-loops-482-via-loop-check

BibTeX

@misc{warmtransfer-claim-sip-forwarding-loops-482-via-loop-check,
  title  = {SIP call forwarding and routing loops: source note sip-forwarding-loops-482-via-loop-check},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/sip-forwarding-loops-482-via-loop-check},
  note   = {Source note sip-forwarding-loops-482-via-loop-check, checked 2026-09-25}
}

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