Cisco BTS 10200 Troubleshooting Manual page 607

Chapter 14 General Troubleshooting
Trunk group states for FAS: Trunk group restore session fail normal, switchover, or maint; or NFAS:
Step 2
NFAS ISDN_DCHAN_STATE_SDN.
This means the Call Agent and the media gateway are not communicating. The backhaul session is not
coming up. The problem has to do with the User Datagram Protocol (UDP) port numbers, IP addresses
or domain name system (DNS) names, or network connectivity. These values are all provisioned in the
Reliable User Datagram Protocol (RUDP) Backhaul Session table in the Call Agent. For Cisco IOS
gateways, these values are part of the session group groupn.....
Things to Check:
Do the four entries in the RUDP Backhaul Session table of the Call Agent match the values in the
a.
gateway (for Cisco IOS gateways, these values are part of session group groupn...)?
If the call-agent-tsap-addr, or the mgw-tsap-addr are DNS names, does nslookup on both Call
b.
Agents resolve the values to one unique IP address?
Can the call-agent-tsap-addr in the four entries be pinged from the media gateway? Do the Call
c.
Agents actually have the IP addresses, or DNS names, specified?
Can the mgw-tsap-addr be pinged from both Call Agents?
d.
Does the trunk-grp isdn-profile exist (show isdn-tg-profile ID=%)? Keep in mind that the profile ID
e.
is case sensitive.
Snoop can be used to see if the gateway and Call Agent are talking in order to establish the session.
f.
Snoop can be used to eliminate whether the problem is on the Call Agent or the media gateway side.
g. The show backhaul session all command on the media gateway can be useful in debugging.
Look at the trace.log on the Call Agent. Search for BSM_create_ss or bsm_create_ss. This shows
h.
the exact values used by the Call Agent.
Note
Trunk group states for FAS: Trunk group restore establish fail normal, switchover, or maint or NFAS:
Step 3
ISDN_DCHAN_STATE_OOS.
This means the specific ISDN channel could not be restored. This is likely related to ISDN layer1 or
layer2 not being up, or related to DCHAN-SLOT and DCHAN-PORT in the ISDN D Channel table. The
media gateway and Call Agent are communicating successfully (session came up).
OL-8723-19
Backhaul deletion is triggered by all trunk groups of a backhaul-set being in the admin-oss state.
Backhaul creation is triggered by controlling one of the trunk groups to in service (INS). The
trunk group list can be determined by using the show isdn-dchan set-id command.
Cisco BTS 10200 Softswitch Troubleshooting Guide, Release 5.0.x
Protocol Troubleshooting
14-33