What DNS service record is required to federate to Cisco Expressway-E?
Is “_xmpp-server.tcp.xmpphostname.domain” in the DMZ?
I have no experience with Cisco Expressway-E. For Openfire to be able to federate with it, it needs to implement the XMPP specifiations.
Openfire (as well as any other spec-compliant XMPP server) will try to resolve the host for a remote XMPP domain by querying for the XMPP DNS SRV records, using the template:
_xmpp-server._tcp.example.net.
where example.net is the XMPP domain name (note that in your example, tcp is used instead of _tcp).
A response to this query could include a record like this one:
_xmpp-server._tcp.example.net. 86400 IN SRV 10 10 5269 server3.example.net.
This signifies that server3.example.net is the FQDN of a server that provides the XMPP service for the example.net domain. An A-record lookup should be used to find the corresponding IP address of the server.
When no DNS SRV records are found, then Openfire will attempt to perform an A-record lookup using the XMPP domain name. This will work for instances where the XMPP domain name equals the FQDN of the server that’s running Openfire.
Cisco Expressway-E is acting as an XMPP server. It is federated with Openfire XMPP by DNS SRV records.
Thanks for your explanation.