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This chapter provides troubleshooting information about connectivity and performance problems in the physical interfaces of a switch router.
The chapter includes the following sections:
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Note For detailed cabling and hardware information for each port adapter, refer to the ATM Port Adapter and Interface Module Installation Guide. The default configurations for the various port adapters are described in the "Configuring Interfaces" chapter in the ATM Switch Router Software Configuration Guide. |
This section outlines the steps for performing basic interface checks and verifies that an ATM switch router interface is enabled and functioning correctly.
Always check the following when an interface fails:
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Note Just because the connector fits, does not mean the wires in the cable are necessarily cross-connected correctly, and the cable is not necessarily the correct type. |
Use the following command to check the ATM physical interface configuration:
Follow these steps to troubleshoot the physical interface:
Step 2 Check the ATM or constant bit rate (CBR) field to see whether the interface is up.
If down, check for the following:
If administratively down, the interface has been administratively taken down. Use the no shutdown interface configuration command to reenable the interface.
Step 3 Check the line protocol field to see whether the status is up.
If down, check for the following:
Step 4 Check the Encapsulation field. Confirm that the encapsulation method matches the interface type.
Step 5 Check the Last input and Last output fields. They show the number of hours, minutes, and seconds since the last packet was successfully received or transmitted by the interface.
Step 6 Check the output hang field. It shows the number of hours, minutes, and seconds since the last reset caused by a lengthy transmission.
Step 7 Check the cyclic redundancy check (CRC) field. The presence of many CRC errors, but not many collisions, indicates excessive noise. If the number is too high, check the cables for damage. If you are using unshielded twisted-pair (UTP) cables, make sure you are using category 5 cable and not another type, such as category 3.
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Note Errors and the input and output difference should not exceed 0.5 to 2.0 percent of traffic on the interface. |
Step 8 Check the collisions field. It shows the total number of collisions compared to the total number of output packets and should be approximately 0.1 percent or less. If the number is too high, perform the following tasks:
If you determine that the physical interface is configured incorrectly, refer to the "Configuring Interfaces" chapter in the ATM Switch Router Software Configuration Guide for configuration information.
If you still have not determined the problem, continue with the next phase of basic interface troubleshooting.
This procedure determines if the cell rate for an interface is correctly configured.
Use the following command to check the cell rate on a physical interface:
Use the following steps to check the cell rate of the interface:
Step 2 Check the IF (interface) Status and Admin (administration) Status fields to see whether they are up.
If down, check for the following:
If administratively down, the interface has been administratively taken down. Use the no shutdown interface configuration command to reenable the interface.
Step 3 Check the Input cells and Output cells fields. If the errors and the input and output difference exceed 0.5 to 2.0 percent of traffic on the interface, the interface is experiencing congestion and dropping cells.
Step 4 Check the AAL5 CRC errors field. If the errors and the input and output difference exceed 0.5 to 2.0 percent of traffic on the interface, check for the following:
If you determine that the physical interface is configured incorrectly, refer to the "Configuring Interfaces" chapter in the ATM Switch Router Software Configuration Guide for configuration information. If you still have not determined the problem, continue with the next phase of basic interface troubleshooting.
To check ATM connection reachability and network connectivity, use the ping atm interface atm command in either privileged or user mode. You can use either an IP address or an ATM address prefix as a ping destination. You can also ping a neighbor switch router by selecting the segment loopback option. In privilege extended command mode, you can select other parameters such as repeat count and timeout values.
| Command | Purpose |
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ping atm interface atm card/subcard/port vpi vci {atm-prefix prefix | end-loopback | |
Follow these steps to ping a specific ATM prefix in both normal and extended mode:
Step 2 Check the Success rate field. It should be 100 percent. If not, check the interface configuration.
Step 3 Use the ping atm interface atm command, in extended mode, to confirm connectivity through a specific interface to an ATM address prefix and modify the default repeat or timeout.
Step 4 Check the Success rate field. It should be 100 percent. If not, check the interface configuration.
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Note If you skip both destination IP address and the ATM prefix fields, the extended ping considers its neighbor switch as its destination and uses a segment-Loopback operation, administration, and maintenance (OAM) cell. In an IP address or ATM prefix case, the ping command always uses an end-to-end OAM loopback cell. |
If the success rate is less than 100 percent, refer to the "Configuring Interfaces" chapter in the ATM Switch Router Software Configuration Guide and confirm the interface configuration.
OAM performs fault management and performance management functions at ATM management-plane (M-plane) layer.
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Note Current OAM implementation supports only the fault management function, which includes connectivity verification and alarm surveillance. |
The ATM switch router fully supports the following ATM OAM cell flows:
You can configure both F4 and F5 flows as either end-to-end or segment-loopback, and they can be used with alarm indication signal (AIS) and remote defect indication (RDI) functions.
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Note Cells can be sent either on demand or periodically to verify link and connection integrity. |
In addition to the standard OAM functions, the ATM switch router can also send OAM pings. See the "Determining Network Connectivity" section. Using OAM cells containing the ATM node addresses or IP addresses of intermediate switch routers, you can determine the integrity of a chosen connection at any intermediate point along that connection. With this information, you can debug and troubleshoot the network connection.
OAM software implements ATM Layer F4 and F5 OAM fault management functions. OAM performs standard loopback (end-to-end or segment) and fault detection and notification (AIS and RDI) for each connection. It also maintains a group of timers for the OAM functions. When there is an OAM state change such as loopback failure, OAM software notifies the connection management software. The network operator can enable or disable OAM operation for the following ATM switch router components:
OAM AIS, RDI, and loopback operations are enabled or disabled for the entire switch router using the atm oam command in global configuration mode. Use the atm oam command in interface mode to configure OAM on a specific connection. For more information about configuring OAM operations, refer to the "Configuring Operation, Administration, and Maintenance" chapter in the
ATM Switch Router Software Configuration Guide .
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Note These OAM configuration commands are not stored in the nonvolatile random-access memory (NVRAM). |
If OAM operation is disabled, outgoing OAM cells are not generated, and all incoming OAM cells are discarded.
To support various OAM operations, the ATM switch router hardware provides OAM cell routing functions on a per-connection basis for each direction and for different OAM cell spans (segment and end-to-end). The hardware OAM cell routing determines the destination of an OAM cell received from the link or the network and then determines whether OAM cells are processed by the ATM switch router software.
The hardware can perform the following functions on OAM cells:
An ATM connection consists of a group of network points, which are the edges of each ATM switch router or end system.
Each point can be one of the following:
Figure 5-1 shows the various loopback operations available.
You can use the loopback test to pinpoint faults by looping a signal at various points in the network. Use the loopback test before and after the initiation of service. Figure 5-2 shows how ATM OAM cell loopbacks are performed first across the interface and then across different segments of the connection.
An ATM switch router generates the OAM cells and forwards them to another network element, which is responsible for returning them to the generating network elements.
Each loopback cell contains the ID of the generating network element and the ID of the network element that is looping the cells back to the originator. Any intermediate site must pass the cells on to the loopback site (the farthest point to which the cells progress) and the generating site (the point to which the cells return).
See "ATM Cell Structures," for a format description of the OAM loopback cell.
The ATM switch router provides the following three types of loopback tests:
The following examples show how to perform loopback tests on the interfaces shown in Figure 5-3.
If users connected to the Fast Ethernet Catalyst 5000 switch in the manufacturing building are not able to connect to the other users outside their building (including the DNS server in the administration building), you should try a loopback test. Use the procedures described in this section to test the ATM switch router connections starting at the middle section and proceeding outward.
Use the atm ping command to confirm the ATM connection between the administration and manufacturing buildings.
| Command | Purpose |
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ping atm interface atm card/subcard/port vpi [vci] [atm-prefix prefix] | [end-loopback] | [ip-address ip-address] | [seg-loopback]} |
Perform the interface loopback tests in the following order:
Test 1—Segment network-side loopback between ATM switch router AdminFl1Ls1, interface 1/0/0, and ATM switch router ManuFl1Ls1, interface 4/0/1
Test 2—Segment link-side loopback between the DNS server and ATM switch router AdminFl1Ls1, interface 4/0/0
Test 3—End-to-end loopback between the DNS server and the Catalyst 5000 Fast Ethernet switch, ManuFl1CaS1, interface 1/1
Follow these steps to ping the ATM virtual channel 2, 130 between the administration and manufacturing buildings, with a segment loopback signal in normal mode:
Step 2 Use the same command to ping the ATM virtual channel 2, 130 between the administration and manufacturing buildings with a segment loopback signal in normal mode:
Step 3 Check the Success rate field. If the success rate is less that 100 percent, you have a problem on the 622-Mbps connection between the administration and manufacturing buildings.
Step 4 Check the cables and the interface configuration, using the procedures in the "Performing Basic Interface Checks" section.
If the success rate is 100 percent, then this segment of the connection is not the problem. Proceed with the next phase of the interface loopback test.
Log in to the ATM switch router in the manufacturing building and use the ping atm interface atm command again to confirm the ATM connection between the ATM switch router and the Catalyst 5000 switches in the manufacturing building.
Use the following steps to ping the ATM virtual path 2 between the ATM switch router and the Catalyst 5000 switches in the manufacturing building, with a segment loopback signal in normal mode:
Step 2 Check the Success rate field. If the success rate is less that 100 percent, there is a problem on the OC-3 155-Mbps connection between the ATM switch router and the Catalyst 5000 switch in the manufacturing building.
Step 3 Check the cables and the interface configuration, using the procedures in the "Performing Basic Interface Checks" section.
If the success rate is 100 percent, then this segment of the connection is not the problem. Proceed with the next phase of the interface loopback test.
Check the end-to-end connection between the DNS server and the Catalyst 5000 switch in the manufacturing building.
Following is an example of the steps to ping the entire ATM virtual path between the administration and manufacturing buildings, with an end-to-end loopback signal in normal mode:
Step 2 Check the Success rate field. If the success rate is less that 100 percent, you have a problem on the OC-3 155-Mbps connection between the ATM switch router and the Catalyst 5000 switch in the manufacturing building.
Step 3 Check the cables and the interface configuration using the procedures in the "Performing Basic Interface Checks" section.
If the success rate is 100 percent, then this segment of the connection is not the problem. Continue with the next phase of the interface test.
The debug privileged EXEC commands can provide a wealth of information about the traffic being seen (or not seen) on an interface.
For detailed information about using the debug commands, see "Debugging a Switch Router."
To isolate problems and troubleshoot the physical connections of the ATM switch router, use the following debug commands in privileged EXEC mode. Use the no form of these commands to disable debugging.
| Command | Purpose |
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debug ports {aal5 [interface atm card/subcard/port] | dcu | ds3e3 | netclock | oc12 | oc3 | t1e1} |
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Refer to the "Configuring Interfaces" chapter in the ATM Switch Router Software Configuration Guide to confirm the interface configuration.
This section describes specific processes and commands used to troubleshoot the 155-Mbps and 622-Mbps port adapters.
The port adapter faceplate LEDs provide status information for individual 155-Mbps and 622-Mbps single-mode and multimode fiber-optic and UTP interface connections of the port adapter. The LEDs are described in Table 5-1.
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Note Use the show controllers command to display the LED status. |
| 1LOS = loss of signal
2LOF = loss of frame 3LCD = loss of cell delineation 4AIS = alarm indication signal 5FERF = far-end receive failure |
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Note Single-mode fiber-optic interface connectors are blue, and multimode connectors are black. |
To display the interface configuration, use the following commands:
| Command | Purpose |
|---|---|
Follow these steps to troubleshoot a 155-Mbps or 622-Mbps physical interface:
Step 2 Check the ATM field to see whether the interface is up.
If down, check for the following:
If administratively down, the interface has been administratively taken down. Use the no shutdown interface configuration command to reenable the interface.
Step 3 Check the line protocol field to see whether the status is up.
If down, check for the following:
Step 4 Check the Encapsulation field. Confirm that the encapsulation method matches the interface type.
Step 5 Check the Last input and Last output fields. They show the number of hours, minutes, and seconds since the last packet was successfully received or transmitted by the interface.
Step 6 Check the output hang field. It shows the number of hours, minutes, and seconds since the last reset caused by a lengthy transmission.
Step 7 Check the CRC field. The presence of many CRC errors, but not many collisions, indicates excessive noise. If the number of errors is too high, check the cables for damage. If you are using UTP cable, make sure you are using category 5 cables and not another type, such as category 3.
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Note Errors and the input and output difference should not exceed 0.5 to 2.0 percent of traffic on the interface. |
Step 8 Check the collisions field. It shows the total number of collisions compared to the total number of output packets, and it should be approximately 0.1 percent or less. If the number is too high, perform the following tasks:
If you determine that the physical interface is configured incorrectly, refer to the "Configuring Interfaces" chapter in the ATM Switch Router Software Configuration Guide .
Follow these steps to show the configuration of a 155-Mbps or 622-Mbps interface:
Step 2 Check the IF Status and Admin Status fields to see whether they are up.
If down, check for the following:
If administratively down, the interface has been administratively taken down. Use the no shutdown interface configuration command to reenable the interface.
Step 3 Check the Input cells and Output cells fields. If the errors and the input and output difference exceed 0.5 to 2.0 percent of traffic on the interface, the interface is experiencing congestion and dropping cells.
Step 4 Check the AAL5 crc errors field. If the errors and the input and output difference exceed 0.5 to 2.0 percent of traffic on the interface, check for the following:
If you determine that the physical interface is configured incorrectly, refer to the "Configuring Interfaces" chapter in the ATM Switch Router Software Configuration Guide .
Follow these steps to display the memory management and error counters of a 155-Mbps or 622-Mbps ATM interface:
