| 1: | What is the command to see the status of the D channel of the IOS-based ISDN router? In which mode of the IOS router can you type the command? |
| A1: | The command is show interfaces bri 0. The command is available for both privileged and user modes. |
| 2: | If you want to see what IP address has triggered the last call in Cisco 77x router, what command should you type? |
| A2: | The command is Router> show packet
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| 3: | What do you look for in the output of the IOS command Router# sh isdn status to be sure if the physical layer in BRI is functional? |
| A3: | Look for Layer 1 Status: ACTIVE. Any other message shows physical layer issues. |
| 4: | What IOS command enables you to distinguish between internal and external ISDN issues? |
| A4: | The IOS command is Router#debug bri. If the router is sending requests for establishment of the activation bit and the response is not coming back, the possible issues are external. If there is no request from the router, concentrate your attention to it. |
| 5: | If you want to debug Layer 2 of ISDN, what is the first IOS command you have to type? |
| A5: | The command is Router# debug isdn Q921
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| 6: | Under normal circumstances, what messages should you not see from the output of Router# debug isdn q921 ? |
| A6: | Under normal circumstances, you should not see SABME, IDREQ, and IDASSN messages. Otherwise, you have a clear indication that Layer 2 is trying to reinitialize . |
| 7: | What are you looking for in the output of the IOS command Router# sh isdn status to be sure if Layer 2 is functional? |
| A7: | First, TEIs = number, where the number has to be between 64 and 126. Second, SAPI has to be 0. Third, every line should have State = MULTIPLE_FRAME_ESTABLISHED. |
| 8: | In the output from the command Router# debug isdn q921 , what does TX ->...ai = 127 mean? |
| A8: | ai = 127 means that the BRI is broadcasting and requesting TEI assignment from the ISDN switch. |
| 9: | If you want to debug Layer 3 of ISDN, what is the first IOS command you have to type? |
| A9: | The command is Router# debug isdn q931
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| 10: | What is the bearer capability in Q931 messages for 64 kbps data, 56 kbps data, and voice calls? |
| A10: | 8890 for 64 kbps data call. 0x8890218F means it is a 56-kbps data call. 0x8090A2 means it is a voice call. |
| 11: | What is the name of the message indicating that the LCP negotiation is successful? |
| A11: | Incoming message CONFACK. |
| 12: | What is the recommended IOS command to troubleshoot the dialer traffic when the router makes outgoing data calls? |
| A12: | The command is Router# debug dialer packets
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| 13: | How many lines of PPP CHAP negotiation indicating success can you see in the output of # debug ppp authentication ? |
| A13: | Two lines if the CHAP negotiation is two ways: one for incoming and one for outgoing. If it is one-way CHAP negotiation, there's only one incoming line. |
| 14: | If you receive config nack during the PPP authentication negotiation, what does it mean? |
| A14: | It means that one side is configured for PAP, but the other is configured for CHAP authentication. |
| 15: | When testing the voice features, what are the two recommended IOS commands you can use? |
| A15: | The commands are Router# debug pots csm Router# debug pots driver
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