VoIP: SIP-over-TLS and sRTP: LANCOM Systems

You can use a Windows tool (LANconfig), the Web interface (WEBconfig), the Command-Line Interface (CLI), or SNMP to configure your LANCOM router. In the CLI, you see the used OpenSSL version via sysinfo. Below, I used WEBconfig. Furthermore in the WEBconfig, I found (at least) three paths/views for configuration: (A) Wizard, (B) Hierarchy, and (C) Menu Tree.

Last tested firmware

10.30.0075 = 10.30 Rel (Reference Manual: General, All-IP, Content Filter, Public Spot, WLAN Management)
10.20.0455 = 10.20 RU6 (Reference Manual: General, All-IP)
10.12.0659 = 10.12 RU12 (Reference Manual: General, All-IP)
retested in May 2020 with 10.12.0787-SU15 and 10.20.0637-SU10


Password: has to be changed on first use
HTTPS: enabled on default
Update: File management → Perform a Firmware Upload, or
Extras → Check for Firmware Update, or
Configuration → Management → Software update (→ General) → Check & Update
Trust Anchors: File management → Upload Certificate → File type: SIP - Trusted Certificate Chain Slot 1: PKCS#12
allows several trust anchors in one file; no private key required: openssl pkcs12 -export -in 76.pem -in 8395.pem -nokeys -out common.p12
SIP-URI User: A) Setup Wizard → Setup Voice-over-IP → (Lines) SIP provider and (Users) ISDN users → User defined → … or
B) Configuration → Voice Call Manager → Lines → SIP lines → Add → SIP-ID, or
C) LCOS Menu Tree → Setup → Voice-Call-Manager → Lines → SIP-Provider → Line → Add → User-Id
SIP-URI Host: A) … SIP domain → other…
B) … SIP domain
C) … Domain
Port: 0 (enables DNS-SRV)
SIP-over-TLS: A) … finish wizard and edit via B or C
B) … Signaling encryption: TLS 1.0 and Verify server cert. acc. to: SIP cert. slot 1
C) … Transport: TLSv1 and Verify-Server-Certificate: SIP-Trusted-CA-Slot-1
this is not a minimum version, therefore, you have to know the version(s) of your SIP provider (higher is better)
SDES-sRTP: A) … finish wizard and edit via B or C
B) Speech encryption: Prefer
C) SRTP: Prefer
which is RTP/SAVP, 488, RTP/AVP

To use that new destination line, for example, you change the existing default call-route:
B) Configuration → Voice Call Manager → Call Router → Call routing → Default → Destination line
C) LCOS Menu Tree → Setup → Voice-Call-Manager → Call-Router → Call-Rounting → default → Dest-Line-1

Bad Defaults

SDES-sRTP: [SNMP] Configuration → Voice Call Manager → Users → SIP Users → (Security) Speech encryption: Prefer
This controls SDES-sRTP for users of the internal SIP B2BUA. Default is Ignore but the remaining sRTP options do not get disabled/greyed then.
Signaling DiffServ: [SNMP] Configuration → Voice Call Manager → Extended → (Quality of Service) SIP DiffServ codepoint (DSCP): CS5
Default is CS6; help text is wrong because it states CS1 as default and CS3 as recommendation.
IPv6: [SNMP 2.70.10] Configuration → IPv6 → General → IPv6 enabled
Default is Disabled; remaining defaults look good.

Software Bugs

SHA-2 Digest: ignores algorithm and picks last
DNS-NAPTR: missing
Voice Call Manager (VCM): all TLS clients have an option called Crypto-Algorithms, except the TLS client of the VCM; therefore you cannot disable RC4-MD5 even manually fixed with 10.40.0286
since 10.40, everything allows TLS 1.3, except the VCM
Signaling DiffServ: when using the SIP B2BUA, does not work internally for TCP (and TLS), only for UDP


Bugs: Cipher Suites include RC4 (even MD5) fixed with 10.40.0286
SIP-over-TLS without authentication (no Hostname Validation) fixed with 10.12.0488
Responsible Disclosure: via ticket system
Agents close your case when the issue was handed over to Engineering. Re-opening the ticket does not help, because is gets closed after two months of inactivity automatically. Consequently, you have to monitor the release notes whether your issue was fixed.
Firmware Update: Automatic Update: possible since LCOS 10.20, see… (even beta is possible)
Update Newsletter: LANCOM LCOS Newsflash
Update Newsletter for Release Candidates: LANCOM RC Newsflash


Model Range

Some models require an intermediate update and then a conversion. Please, do not give up to get the latest version and double-check the (Telekom) download page. Some models within a series are End-of-Sale and/or End-of-Life already; please double-check its lifecycle. Anything below 10.20 is not recommend because the automatic firmware update is missing then.

Power Supply

12 V 1.5 A, Coaxial: 5.5 mm × 2.1 mm

back to the other phones.