Source note · SIP ALG problems on firewalls and routers
Under RFC 3261, a server that receives a request whose top Via sent-by host is a domain name, or an IP address that differs from the packet's source address, adds a received parameter carrying the actual source address to that Via.
Checked 2026-09-25
- Vendor
- IETF
- Product
- SIP
- Subsystem
- transport layer
- Deployment
- on-premises, multi-tenant, hybrid
- Region
- not restricted
- Release range
- RFC 3261 June 2002
- Checked
- 2026-09-25
Sources
- RFC 3261 — SIP: Session Initiation Protocol — IETF / RFC Editor · tier 1 standards and regulators · Section 18.2.1 Receiving Requests
Cite this note
APA
WarmTransfer. (2026, September 25). SIP ALG problems on firewalls and routers: source note sip-alg-problems-rfc3261-via-received. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-alg-problems-rfc3261-via-received
BibTeX
@misc{warmtransfer-claim-sip-alg-problems-rfc3261-via-received,
title = {SIP ALG problems on firewalls and routers: source note sip-alg-problems-rfc3261-via-received},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-alg-problems-rfc3261-via-received},
note = {Source note sip-alg-problems-rfc3261-via-received, checked 2026-09-25}
}