Troubleshooting ISDN

Troubleshooting ISDN

本人在碰到一些ISDN的拨号连接问题，结合其他地方碰到的一些问题，在此总结一下，贡献一下，供大家以后调试排错时参考。

某公司调试ISDN拨号到总部时，拨不出去。

1、 Show isdn status，看到ISDN的1层、2层、3层状态均正常。

The current ISDN Switchtype = basic-net3
ISDN BRI0 interface
Layer 1
Status:
ACTIVE
Layer 2
Status:
TEI = 110, State = MULTIPLE_FRAME_ESTABLISHED
Layer 3 Status
:
0 Active Layer 3 Call(s)
Activated dsl 0 CCBs = 0
Total Allocated ISDN CCBs = 0
参考文档：Using the show isdn status Command for BRI Troubleshooting
http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a0080094b78.shtml
2、debug dialer的信息提示：

试图拨叫075526013143，wait for isdn carrier timeout，连接中止。

3、debug isdn q921的信息：

1d15h: ISDN BR0/0: TX -> SABMEp sapi = 0 tei = 64

1d15h: ISDN BR0/0: RX <- UAf sapi = 0 tei = 64

1d15h: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0, TEI 64 changed to up

1d15h: ISDN BR0/0: TX -> INFOc sapi = 0 tei = 64 ns = 0 nr = 0 i = 0x08016D

0504028890180183700D80303735353236303133313433

1d15h: ISDN BR0/0: RX <- RRr sapi = 0 tei = 64 nr = 1

1d15h: ISDN BR0/0: RX <- INFOc sapi = 0 tei = 64 ns = 0 nr = 1 i = 0x0801ED

02180189

1d15h: ISDN BR0/0: TX -> RRr sapi = 0 tei = 64 nr = 1

1d15h: ISDN BR0/0: RX <- INFOc sapi = 0 tei = 64 ns = 1 nr = 1 i = 0x0801ED

45080302809C

1d15h: ISDN BR0/0: TX -> RRr sapi = 0 tei = 64 nr = 2

1d15h: ISDN BR0/0: TX -> INFOc sapi = 0 tei = 64 ns = 1 nr = 2 i = 0x08016D

4D

1d15h: ISDN BR0/0: RX <- RRr sapi = 0 tei = 64 nr = 2

1d15h: ISDN BR0/0: RX <- INFOc sapi = 0 tei = 64 ns = 2 nr = 2 i = 0x0801ED

5A

1d15h: ISDN BR0/0: TX -> RRr sapi = 0 tei = 64 nr = 3.

1d15h: ISDN BR0/0: TX -> RRp sapi = 0 tei = 64 nr = 3

1d15h: ISDN BR0/0: RX <- RRp sapi = 0 tei = 64 nr = 2

1d15h: ISDN BR0/0: RX <- RRf sapi = 0 tei = 64 nr = 2

1d15h: ISDN BR0/0: TX -> RRf sapi = 0 tei = 64 nr = 3

1d15h: ISDN BR0/0: RX <- DISCp sapi = 0 tei = 64

1d15h: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0, TEI 64 changed to down

1d15h: ISDN BR0/0: TX -> UAf sapi = 0 tei = 64

4、debug isdn q931的信息：

1d15h: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0, TEI 64 changed to up.

1d15h: ISDN BR0/0: TX -> SETUP pd = 8 callref = 0x6E

1d15h: Bearer Capability i = 0x8890

1d15h: Channel ID i = 0x83

1d15h: Called Party Number i = 0x80,0755xxxxxxxx
1d15h: ISDN BR0/0: RX <- CALL_PROC pd = 8 callref = 0xEE

1d15h: Channel ID i = 0x89

1d15h: ISDN BR0/0: RX <- DISCONNECT pd = 8 callref = 0xEE

1d15h: Cause i = 0x02809C -

1d15h: ISDN BR0/0: TX -> RELEASE pd = 8 callref = 0x6E

1d15h: ISDN BR0/0: RX <- RELEASE_COMP pd = 8 callref = 0xEE

1d15h: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0, TEI 64 changed to down

5、show isdn his的信息：

所有的呼叫状态都是：in，结果：fail

在这里我们注意到：

1、 ISDN端口状态如果没有流量触发，经过一段时间1层、2层会自动down掉。这个现象和原来调试中石化的时候有些相似，但是有点不一样在于中石化的是端口不断的up,down,up,down，而在这里一旦端口down掉后，就不再up，直到有流量触发端口up。这里我使用的是isdn switch-type basic-net3，即中国普通标准。而当我使用isdn switch-type basic-dms100时，出现端口不断的up,down,up,down，和中石化现象一样。我个人认为可能是各个电信使用的ISDN标准不一样造成的，决定还是使用原来的isdn switch-type basic-net3配置。

参考文档：ISDN Switch Types, Codes, and Values
http://www.cisco.com/en/US/products/sw/iosswrel/ps1826/products_command_reference_chapter09186a008008729f.html
2、 可以看到debug isdn q921的信息显示，路由器和ISDN交换机之间应该是已经建立了正常的连接。

参考文档：Troubleshooting BRI Layer 2
http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a0080094b77.shtml
3、 在debug isdn q931中出现RX <- DISCONNECT pd = 8 callref = 0xEE的信息是在The telco switch responds with a Call Proceeding. This indicates the network is processing the call：RX <- CALL_PROC pd = 8 callref = 0xEE之后的。Any failures of the call past this point are due to higher level issues such as DDR, PPP, Authentication, IPCP/IP Addressing等等。

参考文档：Troubleshooting ISDN BRI Layer 3 Using the debug isdn q931 Command
http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a0080093c1a.shtml
4、 在debug isdn q931出现的信息中红色字体的地方，我发现居然没有原因说明，并且0x02809C这个参数是不对的。正常情况应该是有原因说明，以0x8开头的参数。比如：

Calling#ping 10.10.10.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.2, timeout is 2 seconds:
20:52:14: ISDN BR0: TX -> SETUP pd = 8 callref = 0x2E
20:52:14: Bearer Capability i = 0x8890
20:52:14: Channel ID i = 0x83 20:52:14: Keypad Facility i = 5551111
20:52:15: ISDN BR0: RX <- CALL_PROC pd = 8 callref = 0xAE
20:52:15: Channel ID i = 0x89
20:52:16: ISDN BR0: RX <- PROGRESS pd = 8 callref = 0xAE
20:52:16: Progress Ind i = 0x8A81 - Call not end-to-end ISDN,
may have in-band info
20:52:16: Signal i = 0x01 - Ring back tone on
20:52:34: ISDN BR0: RX <- DISCONNECT pd = 8 callref = 0xAE
20:52:34: Cause i =0x829F08 - Normal,unspecified or Special intercept,call blocked group restriction
20:52:34: ISDN BR0: TX -> RELEASE pd = 8 callref = 0x2E
20:52:34: ISDN BR0: RX <- RELEASE_COMP pd = 8 callref = 0xAE
The 0x in the disconnect code indicates the bytes that follow are in hexadecimal format and is not part of the actual code. After stripping the 0x from the debug output, see the table below for a breakdown of the code in the example above.

Cause i =

0x829F08

Parsed Hex Bytes
82
9F
08

Description
Cause Code Origination Point
Disconnect Cause Code
Optional Diagnostic field

Cause Code Origination Point
The first byte (most significant) after 0x indicates where in the circuit path the Disconnected Cause Code was generated. In the example above, 82 indicates the call was disconnected from the local telco switch. The list below defines the Cause Code Origination Points to help you interpret where the call was disconnected:

? 80 - From the router.

? 81 - From the private network near the local user [(possibly a local private branch exchange (PBX)].

? 82 - From the public network near the local user (local telco switch).

? 83 - From the transit network (in the ISDN cloud).

? 84 - From the public network near the remote user (remote telco switch).

? 85 - From the private the network near the remote user (possibly a remote PBX).

? 87 - From the international network.

? 8A - From a network beyond the internetworking point.

Disconnect Cause Code
The next byte (9F in the above example) that follows the Cause Code Origination Point byte is the Disconnect Cause Code and is significant in troubleshooting. Use the table below to associate a Disconnect Cause Code (in Hex) and the Cause Description to determine the disconnect reason.

Hex Code
Cause Description
Additional Information

80
Normal Disconnect
The call has been disconnected normally

81
Unallocated or unassigned number
The ISDN number is sent to the switch in the correct format. However, the number is not assigned to destination equipment.

82
No route to specified network
The ISDN exchange is asked to route the call through an unrecognized intermediate network.

This cause indicates that the equipment sending this cause has received a request to route the call through a particular transit network which it does not recognize. The equipment sending this cause does not recognize the transit network either because the transit network does not exist or because that p
1045f
articular network, while it does exist, does not serve the equipment that is sending this cause. This cause is supported on a network-dependent basis.

83
No route to destination
The call routes through an intermediate network that does not serve the destination address.

This cause indicates that the called user cannot be reached because the network through which the call has been routed does not serve the destination desired. This cause is supported on a network-dependent basis.

84
Send special information tone
The remote number you dialed could not be reached.

Check the number and verify if you need any prefixes to access the network (for example, dialing a 9 for outbound calls through a PBX) Contact your telco/PBX administrator

85
Misdialled trunk prefix.
The remote number you dialed could not be reached.

Check the number and verify if you need any prefixes to access the network (for example, dialing a 9 for outbound calls through a PBX) Contact your telco/PBX administrator

86
Channel unacceptable
The service quality of the specified channel is insufficient to accept the connection.

The call attempt failed because the channel cannot be used.

If you are using a PBX check the configuration of the PBX. For a PRI check with your telco to determine how many channels are provisioned.

87
Call awarded and delivered in established channel
The user assigns an incoming call that is connecting to an already established call channel.

This cause indicates that the user is receiving an incoming call, which is being connected to a channel already used by that user for similar calls (for example, packet-mode X.25 virtual calls).

88
Preemption
Your call was blocked. This happens, for example, if another call has a higher priority than your call (common with voice calls). Wait and try the call again later.

If you are using a PBX (or the remote site that you are connecting to uses a PBX) check the configuration of the PBX. If the condition persists, contact your telco.

89
Preemption, circuit reserved for re-use
Your call was blocked. This happens, for example, if another call has a higher priority than your call (common with voice calls). Wait and try the call again later.

If either side is connected to a PBX check the configuration of the PBX. If the condition persists, contact your telco.

90
Normal call clearing
Normal call clearing occurs. No action is required

This cause indicates that the call is being cleared because one of the users involved in the call has requested that the call be cleared. Under normal situations, the source of this cause is not the network.

If the call fails with this Disconnect Cause Code, The call is most likely failing at a higher layer protocol such as PPP, authentication or idle timeout related issues. Verify the router configuration.

Also, if you had requested callback, then the remote device will disconnect (and generate this code) and then call you back;

91
User busy
The called system acknowledges the connection request but cannot accept the call because all B-channels are in use. It is noted that the user equipment is compatible with the call.

Note: Note: If you have multiple ISDN circuits, the telco can configure them in a "hunt-group" whereby calls will be switched to the next available circuit.

92
No user responding
The connection fails because the destination does not respond to the call.

This cause is used when a user does not respond to a call establishment message with either an alerting or connect indication within the prescribed period of time allocated (defined in ITU-T Q.931 by the expiry of either timer T303 or T310).

93
No answer from user
The destination responds to the connection request but fails to complete the connection within the prescribed time. This cause is used when a user has provided an alerting indication but has not provided a connect indication within a prescribed period of time. This cause is not necessarily generated by Q.931 procedures but may be generated by internal network timers.

The problem is at the remote end of the connection.

94
Subscriber absent
The remote device you attempted to reach unavailable and has disconnected from the ISDN network.

Contact the person responsible that device.

95
Call rejected
The destination can accept the call but rejects it for an unknown reason.

This cause indicates that the equipment sending this cause does not wish to accept this call, although it could have accepted the call because the equipment sending this cause is neither busy nor incompatible.

96
Number changed
The ISDN number used to set up the call is not assigned to a system.

This cause is returned to a calling user when the called party number indicated by the calling user is no longer assigned. The new called party number may optionally be included in the diagnostic field. If a network does not support this capability, cause No. 81, unassigned (unallocated) number, shall be used.

97
Redirection to new destination
Your call is being routed to a different ISDN number.

Check the number you are calling. Also verify the PBX configuration (if used)

99
Exchange routing error
Your call cannot be successfully routed to the remote party.

Check the number you are calling. Also verify the PBX configuration (if used)

9A
Non-selected user clearing
The destination can accept the call but rejects it because it is not assigned to the user.

9B
Destination out of order
The destination cannot be reached because of an interface malfunction, and a signaling message cannot be delivered. This can be a temporary condition, but it could last for an extended period.

This cause indicates that a signaling message was unable to be delivered to the remote user: for example, a physical layer or data link layer failure at the remote user, user equipment off-line(turned off), so forth and so on

9C
Invalid number format
The connection fails because the destination address is presented in an unrecognizable format, or the destination address is incomplete.

Verify that the format of the number dialed is correct. This includes any appropriate digits for a PBX, long distance, so forth and so on.

9D
Facility rejected
The facility requested by the user cannot be provided by the network.

9E
Response to STATUS ENQUIRY
The status message is generated in direct response to receiving a status inquiry message.

9F
Normal, unspecified
Reports the occurrence of a normal event when no standard cause applies. No action required.

A1
Circuit out of order
There is some problem in the ISDN network so the call cannot go through.

A2
No channel available
The connection fails because no appropriate channel is available to take the call.

A3
Destination unattainable
Destination cannot be reached through the Telco network. Contact the Telco

A4
Out of order
Some part of the network necessary to route the call is out of order.

The destination cannot be reached because of a network malfunction, and the condition can last for an extended period. An immediate reconnect attempt will probably fail.

If you are using a long distance carrier, you may wish to try using a Presubscribed Inter-exchange Carrier (PIC) for example, a 10-10-xyz carrier to verify that problem lies with the long distance carrier.

A6
Network out of order
The destination cannot be reached because of a network malfunction, and the condition can last for an extended period. An immediate reconnect attempt will probably fail.

If you are using a long distance carrier, you may wish to try using a Presubscribed Inter-exchange Carrier (PIC) for example, a 10-10-xyz carrier to verify that problem lies with the long distance carrier.

A7
Permanent frame mode connection out of service
The permanent connection was terminated, probably due to equipment failure.

If the problem persists, contact your telco

A8
Permanent frame mode connection operational
The permanent connection is fully operational again. (The connection was terminated previously, probably due to equipment failure.)

A9
Temporary failure
An error occurs because of a network malfunction. The problem will be resolved shortly. Contact the telco if the problem is persistent

AA
Switching equipment congestion
The destination cannot be reached because the network switching equipment is temporarily overloaded. Try again later

AB
Access information discarded
The network cannot provide the requested access information.

This cause indicates that the network could not deliver access information to the remote user as requested: for example, user-to-user information, low layer compatibility, high layer compatibility, or a sub-address as indicated in the diagnostic. It is noted that the particular type of access information discarded is optionally included in the diagnostic.

AC
Requested channel not available
The remote equipment cannot provide the requested channel for an unknown reason. This can be a temporary problem.

AF
Resources unavailable, unspecified
The requested channel or service is unavailable for an unknown reason. This can be a temporary problem.

B1
Quality of service (QoS) unavailable
The requested quality of service cannot be provided by the network. This can be a subscription problem.

This cause is used to report that the requested QoS, as defined in Recommendation X.213, cannot be provided (for example, the throughput or transit delay cannot be supported).

B2
Requested facility not subscribed
The remote equipment supports the requested supplementary service by subscription only.

This cause indicates that the requested supplementary service could not be provided by the network because the user has not completed the necessary administrative arrangements with its supporting networks.

This error codecan also be returned by the ISDN network when a call attempt is made but the SPIDs have not been entered or are incorrect. Ensure your SPIDs have been entered correctly or contact your telco to verify your SPIDs.

Also verify the speed of the outgoing call is suported by the ISDN network (56k or 64k).

B4
Outgoing calls barred
There is some restriction on outgoing calls. The ISDN network does not allow you to make outgoing calls.

B5
Outgoing calls barred within CUG
There is some restriction on outgoing calls. The ISDN network does not allow you to make outgoing calls.

B6
Incoming calls barred
The ISDN network does not allow you to receive calls.

Contact your telco

B7
Incoming calls barred within CUG
The ISDN network does not allow you to receive calls. Contact your telco

B9
Bearer capability not authorized
The user requests a bearer capability the network provides, but the user is not authorized to use it. This can be a subscription problem.

This cause indicates that the user requested a bearer capability implemented by the equipment generating this cause that the user is not authorized to use.

BA
Bearer capability not presently available
The network normally provides the requested bearer capability, but it is unavailable at the present time. This can be due to a temporary network problem or subscription problem.

If the incoming call is Analog (modem call), verify that you have isdn incoming voice-modem under the PRI or BRI physical interface.

BF
Service/option not available, unspecified
The network or remote equipment cannot provide the requested service option for an unspecified reason. This can be a subscription problem.

C1
Bearer capability not implemented
The network cannot provide the bearer capability requested by the user.

Contact the telco to troubleshoot further

C2
Channel type not implemented
The network or the destination equipment does not support the requested channel type.

C5
Requested facility not implemented
The remote equipment does not support the requested supplementary service.

C6
Only restricted digital info bearer capability available
The network cannot provide unrestricted digital information bearer capability.

This cause indicates that a device has requested an unrestricted bearer service but the equipment sending this cause only supports the restricted version of the requested bearer capability.

CF
Service/option not implemented, unspecified
The network or remote equipment cannot provide the requested service option for an unspecified reason. This can be a subscription problem.

D1
Invalid call reference value
The remote equipment receives a call with a call reference that is not currently in use on the user-network interface.

D2
Identified channel does not exist
The receiving equipment is requested to use a channel that is not activated on the interface for calls.

This cause indicates that the equipment sending this cause has received a request to use a channel not activated on the interface for a call. For example, if a user has subscribed to those channels on a primary rate interface numbered from 1 to 12 and the user equipment or the network attempts to assign a call to channels 13 through 23, this cause is generated.

D3
Suspended call exists, but call id does not
The network receives a call resume request. The call resume request contains a Call Identify (id) information element that indicates the call identity is being used for a suspended call.

This cause indicates that a call resume has been attempted with a call identity which differs from that in use for any presently suspended call(s).

D4
Call id in use
The network receives a call resume request. The call resume request contains a Call Identity information element that indicates the resume request is in use for a suspended call.

This cause indicates that the network has received a call suspend request. The call suspend request contained a call identity (including the null call identity) which is already in use for a suspended call within the domain of interfaces over which the call might be resumed.

D5
No call suspended
The network receives a call resume request when there is not a suspended call pending. This can be a transient error that will be resolved by successive call retries.

This call indicates that the network has received a call resume request. The call resume request contained a call identity information element that presently does not indicate any suspended call within the domain interfaces over which calls may be resumed.

D6
Call with requested call id has been cleared
The network receives a call resume request. The call resume request contains a Call Identity information element that once indicated a suspended call. However, the suspended call was cleared either by time-out or by the remote user.

This cause indicates that the network has received a call resume request. The call resume request contained a call identity information element that once indicated a suspended call; however, that suspended call was cleared while suspended (either by network timeout or by remote user).

D7
User not member of CUG
Your call was not completed, probably due to one of the following reasons:

- The ISDN number you dialed is incorrect. - You requested a service that you are not authorized to use (you have not subscribed to this service). - The remote device is not authorized to use a service that you are using.

Check the number you called. If the problem persists, contact your telco.

D8
Incompatible destination
Indicates that an attempt is made to connect to non-ISDN equipment. (For example, an analog line.)

This cause indicates that the equipment sending this cause has received a request to establish a call that has a low layer compatibility, high layer compatibility, or other compatibility attributes (for example, data rate) that cannot be accommodated.

This code is often seen when the calling device dials the wrong number, and ends up reaching a non-ISDN device. Therefore, verify that the number dialed is correct.

It could also be generated when a a data call wis made to voice number, or a voice call is made to a number that only supports data. If the dialed number is correct, the telco may have configured their switch incorrectly.

DA
Non-existent CUG
Your call was not completed, probably due to one of the following reasons: - The ISDN number you dialed is incorrect. - You requested a service that you are not authorized to use (you have not subscribed to this service). - The remote device is not authorized to use a service that you are using.

Check the number you dialed. If the problem persists, contact your telco.

DB
Invalid transit network selection
The ISDN exchange is asked to route the call through an unrecognized intermediate network.

This cause indicates that a transit network identification of an incorrect format was received. This is defined in Annex C of ITU-T Q.931

DF
Invalid message, unspecified
An invalid message is received with no standard cause. This is usually due to a D-channel error. If the error occurs systematically, report it to your ISDN service provider.

E0
Mandatory IE missing
The receiving equipment receives a message that does not include one of the mandatory information elements. This cause indicates that the equipment sending this cause has received a message that is missing an information element that must be present in the message before that message can be processed.

This is due to a D-channel error. Ensure the switch type is configured correctly. A Cisco IOS® Software upgrade on the router can help alleviate this issue. If the error occurs systematically, report it to your ISDN service provider.

E1
Message type not implemented
The receiving equipment receives an unrecognized message, because the message type is invalid or the message type is valid but not supported. The cause is due to a problem with the remote configuration or with the local D-channel.

E2
Message not compatible with call state or not implemented
The remote equipment receives an invalid message with no standard cause.

This cause indicates that the equipment sending this cause has received a message such that the procedures do not indicate that this is a permissible message to receive while in the call state, or a STATUS message was received indicating an incompatible call state.

The cause is due to a D-channel error. If the error occurs systematically, report it to your ISDN service provider.

E3
IE not implemented
The remote equipment receives a message that includes information elements, that are not recognized.

This cause indicates that the equipment sending this cause has received a message that includes information elements not recognized because the information element identifier is not defined or it is defined but not implemented by the equipment sending the cause. However, the information element is not required to be present in the message in order for the equipment sending the cause to process the message.

This is due to a D-channel error. If the error occurs systematically, report it to your ISDN service provider.

E4

The remote equipment receives a message that includes invalid information in the information element.

This cause indicates that the equipment sending this has received an information element which it has implemented; however, one or more of the fields in the information element are coded in a way that has not been implemented by the equipment sending this cause.

This is due to a D-channel error.

E5
Message not compatible with call state
The remote equipment receives an expected message that does not correspond to the current state of the connection.

This is due to a D-channel error.

E6
Recovery on time expiry
Your call was not completed, probably because an error occurred (for example, a state synchronization error).

You should wait and try the call again later. If the problem persists, contact your ISDN service provider.

E7
Parameter not implemented
Your call was not completed because the ISDN network does not support a service you need to use.

Contact your ISDN service provider.

EF
Protocol error, unspecified
An unspecified D-channel error with no other standard cause.

FF
Interworking, unspecified
An event occurs, but the network does not provide causes for the action it takes. The precise problem is unknown.

??
Unknown Cause value
The cause value is unknown.

参考文档：Understanding debug isdn q931 Disconnect Cause Codes
http://www.cisco.com/en/US/tech/tk801/tk379/technologies_tech_note09186a008012e95f.shtml
5、 show isdn his的信息为什么显示的type都是in呢？我这里应该是拨出――out。

6、 通过此ISDN线路能拨电话到深圳，能上网，说明线路应该没有问题。

最后，我注意到此路由器的IOS版本比较低：12.0(10)。而原来安装此WIC-1B-S/T模块的路由器IOS是12.1(5)T的。根据4，5的异常现象决定先升级路由器的IOS到12.1(5)T。

升级完路由器IOS后，发现还是不能拨号到深圳。但是一些信息出现了变化。

show isdn his的信息提示拨号type变成out，拨号号码是075526013143，可是还是失败。debug isdn q931的信息：

1d15h: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0, TEI 64 changed to up.

1d15h: ISDN BR0/0: TX -> SETUP pd = 8 callref = 0x6E

1d15h: Bearer Capability i = 0x8890

1d15h: Channel ID i = 0x83

1d15h: Called Party Number i = 0x80, 0755xxxxxxxx

1d15h: ISDN BR0/0: RX <- CALL_PROC pd = 8 callref = 0xEE

1d15h: Channel ID i = 0x89

1d15h: ISDN BR0/0: RX <- DISCONNECT pd = 8 callref = 0xEE

1d15h: Cause i = 0x809C - invalid number format(imcomplete number)

1d15h: ISDN BR0/0: TX -> RELEASE pd = 8 callref = 0x6E

1d15h: ISDN BR0/0: RX <- RELEASE_COMP pd = 8 callref = 0xEE

1d15h: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0, TEI 64 changed to down

这里可以看到cause i的信息正常，并且有原因提示。根据提示，怀疑是电信没有开通ISDN到深圳的数据业务或者是ISDN交换机里没有做好长途号码0755的路由信息。和电信联系，让他们检查一下，电信做完路由后，本端再进行测试，终于OK！！！

其他地方碰到的一些问题：

1、 某公司ISDN拨号到银行不通。debug isdn q931的cause i提示Unallocated or unassigned number。查看配置，原来拨号号码前面多加了区号010，市内拨打电话不需要加区号010的。去掉后没有这个提示，但是一拨上去就断开。debug ppp negotiation显示到协商用户名密码的时候fail，原来是用户名密码不匹配。

2、 某公司ISDN拨号到总部，一拨上去就断开。debug ppp negotiation显示到协商用户名密码的时候fail，也来是用户名密码不匹配。

总结：

1、 使用命令

show isdn status 查看ISDN端口状态

show isdn history 查看ISDN拨号历史情况

show dialer 查看拨号情况

debug isdn q921 查看ISDN 2层信息

debug isdn q931 查看ISDN 3层信息

debug dialer 查看拨号信息

debug ppp negotiation 查看ppp协议运行信息

2、 注意参数：

show isdn status中的1，2，3层状态

debug isdn q931中的引起disconnect的原因――cause i

debug ppp negotiation中的用户名密码验证信息

3、 ISDN分为语音和数据业务，能拨电话到目的地并不代表数据传输也能到达，以后配置前要向电信咨询。

4、 注意路由器IOS版本