Yealink SIP-T21 E2 Administrator's Guide

Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones
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Method
Supported
Notes
RAck
Yes
Record-Route
Yes
Refer-To
Yes
Referred-By
Yes
Remote-Party-ID
Yes
Replaces
Yes
Require
Yes
Route
Yes
RSeq
Yes
Session-Expires
Yes
Subscription-State
Yes
Supported
Yes
To
Yes
User-Agent
Yes
Via
Yes
SIP Responses
The following SIP responses are supported:
Note
1xx Responses—Provisional
1xx Response
Supported
Notes
100 Trying
Yes
180 Ringing
Yes
181 Call Is Being Forwarded
Yes
182 Queued
Yes
183 Session Progress
Yes
In the following table, a “Yes” in the Supported column means the header is sent and properly
parsed. The phone may not actually generate the response.

Yealink SIP-T21 E2 Specifications

General

Brand	Yealink
Model	SIP-T21 E2
Category	IP Phone
Language	English