Cisco router problems (1)

This article mainly summarizes some common problems encountered during the use of Cisco routers, and provides detailed solutions to these problems, I believe that reading this article will be of great help to vrouters in the future.

[Problem] 2509 of dial-up users can ping the 2509 asynchronous port and Ethernet port from the asy port after they have switched to the router, however, you cannot ping the server on the Ethernet connected to 2509.

[Solution]: In the network settings on the server, point the gateway in the TCP/IP attribute of the NIC to the Ethernet port of the 2509 router.

[Analysis]: No gateway is set for an Ethernet server. When a packet is forwarded from the router to the server, the server determines from the message that the source address is not the address of this network, and the response packet according to the protocol should be sent to the gateway, however, because no gateway address is set, the server cannot respond to the request. Therefore, the timeout error occurs because the remote terminal cannot receive the message. After the gateway is configured, the server can send a response packet to complete the ping protocol.

[Problem] serious loss of ping to peer after two 2501 leased lines are connected

[Solution]: You can flip the clock on the serial port of the corresponding leased line at both ends, and set the command to inverttransmit-clock.

[Analysis]: serious loss of reports may be due to clock misplacement on the line, which may result in the receiving and sending failures of routers at both ends of the line, turning the clock over inverttransmit-clock on the interface is equivalent to making the clock change for half a cycle and aligning the clock. Inaccurate clock is not the only cause of serious loss. If the problem persists after the clock is changed and the configuration is confirmed correct, check whether the line is normal.

[Problem] When configuring x.25 address ing, a duplicate address ing is prompted.

[Solution]: Run nox25mapip to delete the previous address ing and reconfigure the new address ing.

[Analysis]: In the X.25 address ing, an IP address can only correspond to one x121 address. When an IP address is configured with two different x121 addresses, this will cause a conflict.

[Problem] when a user uses a QUIDWAY router to connect to a wide area network port, the PPP protocol fails and the problem is determined.

[Solution]: The PPP protocol belongs to the second-layer ISO protocol. Therefore, the problem must be determined from the first layer. Use showinsNN as the serial port used.) view the underlying DTR, DSR, RTS, CTS, whether the DCD signal is UP. If not, it indicates that the physical line between the DTE and the DCE is not connected. Check the connection cable. When the serial port prompts UP and there are no error frames, it indicates that the physical layer is normal. If the physical layer is correct, run the showinsN command to check whether the LCP and IPCP are OPEN, such as LCPOPEN and IPCPINITIAL. This indicates that the PPP verification fails and the PPP verification fails.

[Analysis]: PPP protocol failures are generally caused by physical layer problems or verification errors. The physical layer status can be obtained from the query information in the showinsN command. When the physical layer is normal, the serial port must be UP, check whether there are many wrong frames. If there are many wrong frames, the physical layer is faulty, although the serial port prompts UP. After the physical layer issues are eliminated, if you still need to check whether the verification is correct, take PAP as an example.