Cisco Cisco TelePresence Video Communication Server Expressway
Appendix 1 – Troubleshooting
Cisco VCS Deployment Guide: Microsoft OCS 2007 R2, Lync 2010 and Cisco VCS X7.0
Page 76 of 104
<sip:10.10.2.1>;tag=d29350afae33”. This is usually caused by a misconfigured SIP URI in the
endpoint. In future versions of B2BUA, the “From”-header will be manipulated if necessary to avoid
this issue.
endpoint. In future versions of B2BUA, the “From”-header will be manipulated if necessary to avoid
this issue.
Call connects but clears after about 30 seconds
If a call connects but shortly later clears, this is likely to be because the caller’s ACK response to the
200 OK is not being properly routed. To resolve this, make sure that the VCS and OCS/Lync servers
are able to resolve each other’s FQDNs In DNS.
200 OK is not being properly routed. To resolve this, make sure that the VCS and OCS/Lync servers
are able to resolve each other’s FQDNs In DNS.
Cisco VCS to OCS/Lync server calls fail – DNS server
Cisco VCS needs to have details about DNS names of OCS/Lync pools and servers, and therefore
needs to have one of its DNS entries set to point to a DNS server which can resolve the FQDNs of the
OCS/Lync pools and servers.
needs to have one of its DNS entries set to point to a DNS server which can resolve the FQDNs of the
OCS/Lync pools and servers.
Cisco VCS to OCS/Lync calls fail – Hardware Load Balancer
If the OCS/Lync environment has FEPs with an HLB in front, ensure that the Cisco VCS is neighbored
with the HLB. If it is neighbored with an FEP directly, trust for VCS will be with the FEP. VCS will send
call requests to the FEP, but the FEP will record-route the message such that the ACK response
should be sent to the HLB. The ACK sent to the HLB gets rejected by OCS/Lync server, so OCS/Lync
clears the call after the SIP timeout due to the FEP not seeing the ACK.
with the HLB. If it is neighbored with an FEP directly, trust for VCS will be with the FEP. VCS will send
call requests to the FEP, but the FEP will record-route the message such that the ACK response
should be sent to the HLB. The ACK sent to the HLB gets rejected by OCS/Lync server, so OCS/Lync
clears the call after the SIP timeout due to the FEP not seeing the ACK.
(Calls MOC/Lync client – registered to the FEP – to Cisco VCS may still work.)
Media problems in calls involving external MOC/Lync
clients connecting via an Edge server
clients connecting via an Edge server
RTP over TCP/UDP
The Edge server supports RTP media over both TCP and UDP, whereas the B2BUA and standards
based video endpoints only support RTP over UDP. The Edge server and any firewalls that the Edge
server may pass media traffic through may need to be reconfigured to allow RTP over UDP as well as
RTP over TCP to be passed.
based video endpoints only support RTP over UDP. The Edge server and any firewalls that the Edge
server may pass media traffic through may need to be reconfigured to allow RTP over UDP as well as
RTP over TCP to be passed.
ICE negotiation failure
This can usually be detected by the call clearing with a BYE with reason header “failed to get media
connectivity”.
connectivity”.
Video endpoints only support UDP media. ICE usually offers 3 candidates:
Host (private IP)
Server Reflexive (outside IP address of firewall local to the media supplying agent – B2BUA or
MOC/Lync Client)
MOC/Lync Client)
TURN server (typically the Edge Server/VCS Expressway)
For ICE to work where an endpoint is behind a firewall, the endpoint must offer at least one publicly
accessible address (the Server Reflexive address or the TURN server address). This is used both for
the B2BUA to try and send media to, but also to validate bind requests sent to the VCS Expressway’s
TURN server – bind requests are only accepted by the TURN server if they come from an IP address
that is ‘known’.
accessible address (the Server Reflexive address or the TURN server address). This is used both for
the B2BUA to try and send media to, but also to validate bind requests sent to the VCS Expressway’s
TURN server – bind requests are only accepted by the TURN server if they come from an IP address
that is ‘known’.
If an OCS/Lync INVITE offers only host candidates for UDP, e.g.: