Screensharing fails to external User

Question

Hey Guys
Im experiencing a Problem with Lync 2013 and i think it is a bit strange.
While most services work flawless, 2 services refuse to work with external user (communication between internal and external user). Filesharing and Screensharing dont work and i really cant figure out why. I have added the Eventlog entry from the client wich
i think is the most relevant entry i have.
Eine von Lync durchgeführte SIP-Anforderung verursachte einen unerwarteten Fehler (Statuscode 80ef025b). Die folgenden technischen Daten enthalten 
weitere Informationen:
 RequestUri:   sip:[email protected]
From:         sip:[email protected];tag=2dafb22801
To:           sip:[email protected];tag=8d42f9ccf6
Call-ID:      10be437364984b7e9a476958769de0ca
Content-type: application/sdp;call-type=applicationsharing
v=0
o=- 0 0 IN IP4 E.E.E.E
s=session
c=IN IP4 E.E.E.E
b=CT:99980
t=0 0
m=applicationsharing 53017 TCP/RTP/AVP 127
a=ice-ufrag:/f81
a=ice-pwd:ktGeRzGw15/LLAozFki/BkSM
a=candidate:1 1 TCP-PASS 2120613887 I.I.I.I 24083 typ host 
a=candidate:1 2 TCP-PASS 2120613374 I.I.I.I 24083 typ host 
a=candidate:2 1 TCP-ACT 2121006591 I.I.I.I 28044 typ host 
a=candidate:2 2 TCP-ACT 2121006078 I.I.I.I 28044 typ host 
a=candidate:3 1 TCP-PASS 174455807 E.E.E.E 53017 typ relay raddr I.I.I.I rport 2802 
a=candidate:3 2 TCP-PASS 174455294 E.E.E.E 53017 typ relay raddr I.I.I.I rport 2802 
a=candidate:4 1 TCP-ACT 174848511 E.E.E.E 53017 typ relay raddr I.I.I.I rport 2802 
a=candidate:4 2 TCP-ACT 174847998 E.E.E.E 53017 typ relay raddr I.I.I.I rport 2802 
a=cryptoscale:1 client AES_CM_128_HMAC_SHA1_80 inline:zzupVB3Gq9vmnuVVA6QLDfyx2lHhcukLm577IE32|2^31|1:1
a=crypto:2 AES_CM_128_HMAC_SHA1_80 inline:eSP2MH6wMVDNE+wEz344m+JLCrMH3hCqlqJn73ue|2^31|1:1
a=crypto:3 AES_CM_128_HMAC_SHA1_80 inline:vU9vOo4MssEopZkEJ1Zz20Ii/CrzR9AniWR234+u|2^31
a=setup:active
a=connection:new
a=rtcp:53017
a=mid:1
a=rtpmap:127 x-data/90000
a=x-applicationsharing-session-id:1
a=x-applicationsharing-role:sharer
a=x-applicationsharing-media-type:rdp
Response Data:
101  Progress Report
ms-diagnostics:  13004;reason="Request was proxied to one or more registered endpoints";source="Internal-Server-FQDN";Count="2";appName="InboundRouting"
180  Ringing
603  Decline
(null):  51004; reason="Action initiated by 
user";OriginalPresenceState="0";CurrentPresenceState="0";MeInsideUser="Yes";ConversationInitiatedBy="0";SourceNetwork="0";RemotePartyCanDoIM="No"
 Lösung:
 Wenn dieser Fehler weiterhin auftritt, wenden Sie sich an den Netzwerkadministrator. Der Netzwerkadministrator kann den oben aufgelisteten Fehlercode 
mit einem Tool, z. B. "winerror.exe" aus dem Resource Kit für Windows oder "lcserror.exe" aus dem Office Communications Server Resource Kit, 
auswerten.
I.I.I.I = internal Server IP
E.E.E.E = External Server IP
xxx = user1 (external)
yyy = user2 (internal)
Thanks for reading
Fresher

Answer 1

Hi Fresher7,
Please verify the following ports are opened on the Firewall.
1. Port :  3478   UDP
Preferred path for A/V media transfer between internal and external users, Survivable Branch Appliance or Survivable Branch Server.
2. Port : 
443 or others (A/V Edge port that you defined in the Topology)   TCP
Fallback path for A/V media transfer between internal and external users, Survivable Branch Appliance or Survivable Branch Server if UDP communication cannot be established,
TCP is used for file transfer and desktop sharing.
Best regards,
Eric