Source note · SIP ALG problems on firewalls and routers
RFC 4787 observes that some NATs keep ALGs such as the SIP ALG permanently on, some turn them on by default but allow them to be turned off, and some leave them off by default but allow them to be turned on.
Checked 2026-09-25
- Vendor
- IETF
- Product
- NAT devices
- Subsystem
- NAT behaviour
- Deployment
- on-premises, multi-tenant, hybrid
- Region
- not restricted
- Release range
- BCP 127 January 2007
- Checked
- 2026-09-25
Sources
- RFC 4787: Network Address Translation (NAT) Behavioral Requirements for Unicast UDP (BCP 127) — IETF / RFC Editor · tier 1 standards and regulators · Section 7 second paragraph
Cite this note
APA
WarmTransfer. (2026, September 25). SIP ALG problems on firewalls and routers: source note sip-alg-problems-rfc4787-default-states-vary. WarmTransfer. https://warmtransfer.net/knowledge/claims/sip-alg-problems-rfc4787-default-states-vary
BibTeX
@misc{warmtransfer-claim-sip-alg-problems-rfc4787-default-states-vary,
title = {SIP ALG problems on firewalls and routers: source note sip-alg-problems-rfc4787-default-states-vary},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/sip-alg-problems-rfc4787-default-states-vary},
note = {Source note sip-alg-problems-rfc4787-default-states-vary, checked 2026-09-25}
}