Port 11720H.323 Call Control Signalling Alternate

Alternate TCP/UDP port assigned for H.323 call-control signalling.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 5/10
lookups: 0

also known as h323callsigalt, H.323 call signalling alternate

Technical Details

what runs on :11720

Port 11720 is assigned for alternate H.323 call-control signaling, principally the H.225/Q.931 call-signaling exchange used to establish, maintain, and terminate H.323 calls. The usual H.323 call-signaling port is TCP 1720; implementations using this alternate assignment may listen on TCP 11720, while the IANA registration also covers UDP. H.323 RAS normally uses UDP 1719, and negotiated media uses separate RTP/RTCP ports. Signaling is not encrypted by default; deployments requiring protection may use H.235 mechanisms or transport security supported by the implementation.

Security Information

exposure of :11720

risk score

5/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

voice and chat averages 3.3 across 181 ports — this one sits 1.7 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

An internet-facing H.323 listener can reveal endpoint and gateway details, receive unsolicited call-setup traffic, and be targeted for denial of service, call abuse, or implementation vulnerabilities. It should normally be restricted to trusted peers or protected with access controls and signaling authentication; H.323 signaling and call metadata should not be assumed confidential.

Record

iana registry entry

port: :11720
service: H.323 Call Control Signalling Alternate
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 5/10caution
category: Voice and Chat
usage: This port carries H.323 call-control signaling between VoIP endpoints, gateways, and conferencing systems that use the alternate assignment. Most H.323 deployments use TCP port 1720 instead, so port 11720 is encountered less often and usually reflects a configured alternate or vendor-specific deployment.
lookups: 0rank 993
added: 2026-08-25
updated: 2026-09-22
references: IANA service name registry — port 11720

Something wrong?

This record is maintained by the engineers who use port 11720. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-09-22.

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edit this record →back to the registry

Related Ports

all 181 in voice and chat →

the 8 most looked-up other ports in voice and chat — 181 ports carry that label.

port	service	proto	category	risk	views
:9090	Openfire Admin Console	TCP	Web Services	caution	34.2k
:1513	Garena Gaming	TCPUDP	Gaming	caution	33.1k
:9091	Openfire Admin Console (SSL)	TCPtls	Web Services	caution	28.3k
:2031	Mobrien Chat	TCPUDP	Web Services	caution	27.7k
:1720	H.323 Signaling	TCP	Network Services	caution	26.5k
:6005	Camfrog Chat	TCP	Voice and Chat	caution	25.2k
:3001	Miralix Phone Monitor	TCP	Network Services	caution	21.7k
:9009	Pichat Server	TCPUDP	Network Services	caution	19.7k

risk mix of the 8 listed

caution100%

1 of 8 encrypted

Port :11720H.323 Call Control Signalling Alternate

Technical Details

Security Information

Related Ports

Port 11720H.323 Call Control Signalling Alternate