Block tcp port 7070 on the inside network and remove the fixup rtsp from the config.
example:
access-list inside deny tcp any any eq 7070
access-list inside permit ip any any
access-group inside in interface inside
# This will block all outbound tcp 7070 connections
# from the inside interface.
no fixup protocol rtsp 554
# Real-Audio uses rtsp if there is no fixup there cannot be real-audio.
Try this !!
Some information:
REAL AUDIO, tcp port 7070, udp ports 6170-7170, Rather than just opening these ports a slightly safer configuration can be achieved by careful configuration of the TCP port connection. The TCP port 7070 is used by the client to initiate a conversation with an external RealServer, to authenticate the player to the server, and to pass control messages during playback (e.g., pausing or stopping the audio stream). Since you do not want incoming connection attempts on this port, you should configure the router's access control list to allow TCP connections on port 7070 to be initiated from the inside network exclusively. Incoming traffic, on the other hand, should only be allowed if it is part of an ongoing connection. This is assured by requiring incoming TCP packets to have the ACK bit set in the TCP header carried by every packet. The syntax for specifying that the ACK bit must be set varies with the kind of router you own, but for Cisco routers the flag "ESTABLISHED" can be put at the end of the line in an access rule to specify that an incoming packet must be part of an ongoing conversation.
http://www.linnetsol.co.uk/port-filter.asp
Real Time Streaming Protocol (RTSP)
http://www.cisco.com/en/US/products/sw/secursw/ps2120/products_configuration_guide_chapter09186a008017278b.html#wp1063957
sincerely
Patrick
