Topology: Softswitch---Eudemon firewall---Eudemon 2200---IAD
Symptoms: IAD fails to register to Eudemon2200 because the firewall denies the registration packets from the Softswitch.
1. Uses could register well but fail to call, without dialing tone after offhook. Execute display sbc reg-user all command, and registered users are found.
2. Execute debug sbc mgcp packet command, and SBC has received the RSIP packets for registration from IAD.
3. Check the packets captured at the port connecting SBC to the Softswitch, and SBC keeps transmitting RSIP packets for registration to the Softswitch, but it gets no response; that is, registration at Softswitch fails.
4. According to the topology, the Softswitch is connected with a firewall; according to packets captured, the firewall discards the RSIP registration packets forwarded by SBC, without reaching the Softswitch.
5. Enable the relevant rules of firewall, and then register again, solving the problem.
1. IAD is problematic.
2. The configuration of SBC is problematic.
3. The Softswitch is problematic.
SBC is an agent equipment, and also one Softswitch for SBC at the peer; however, for the Softswitch, SBC is client. The case results from that the Softswitch does not echo to the MGCP packets forwarded by SBC.