I've successfully federated CUP Server with Lync 2010 via direct federation. Both Jabber and lync can see each others presence status and can send messages to each other.
Unfortunately, there is one big issue: After a while, lync clients losing the presence information of the jabber clients. Lync says "presence unknown".
After a double-click on the contact, the presence status changes several times between "online" and "presence unknown" and finally stays at "online". After 5 or 10 minutes, the presence status changes back to "unknown presence status". This issue only happens on lync-side with jabber clients. The presence status on the other side (on jabber client, presence status of lync users) is always correct.
I already found this document: http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/im_presence/interdomain_federation/9_1_1/CUP0_BK_IB27169E_00_interdomain-federation-integration-guide-9_1_1_chapter_01110.html#CUP0_RF_L485A250_00
but this is just in assouciation with lync edge server. I do not use it, I have a direct federation. Second point is, I am always able to send and receive messages, just the presence status is not working correctly.
Per Microsoft, installing the XMPP service on the Front end service is not supported, an Edge server is required. Not sure if that helps but thought I would mention.
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thanks for your answer. Maybe I missed it to mention in my main post, the federation is done via the SIP proxy on CUP side.
On Lync side there are just the static route for my CUP domain and the trusted host entries.