Overview of Troubleshooting
This chapter introduces the basic concepts, methodology, and general troubleshooting guidelines for problems that may occur when configuring and using Cisco Nexus 1000V.
This chapter includes the following sections:
Overview of the Troubleshooting Process
To troubleshoot your network, follow these general steps:
Step 1 Gather information that defines the specific symptoms.
Step 2 Identify all potential problems that could be causing the symptoms.
Step 3 Systematically eliminate each potential problem (from most likely to least likely) until the symptoms disappear.
Overview of Best Practices
Best practices are the recommended steps you should take to ensure the proper operation of your network. We recommend the following general best practices for most networks:
- Maintain a consistent Cisco Nexus 1000V release across all network devices.
- Refer to the release notes for your Cisco Nexus 1000V release for the latest features, limitations, and caveats.
- Enable system message logging. See the “Overview of Symptoms” section.
- Verify and troubleshoot any new configuration changes after implementing the change.
This section introduces questions to ask when troubleshooting a problem with Cisco Nexus 1000V or connected devices. Use the answers to these questions to identify the scope of the problem and to plan a course of action.
This section includes the following topics:
By answering the questions in the following subsections, you can determine the paths you need to follow and the components that you should investigate further.
Answer the following questions to determine the status of your installation:
- Is this a newly installed system or an existing installation? (It could be a new host, switch, or VLAN).
- Has the host ever been able to see the network?
- Are you trying to solve an existing application problem (too slow, too high latency, excessively long response time) or did the problem show up recently?
- What changed in the configuration or in the overall infrastructure immediately before the applications started to have problems?
To discover a network problem, use the following general network troubleshooting steps:
Step 1 Gather information on problems in your system. See the “Gathering Information” section.
Step 2 Verify the layer 2 connectivity. See the “Verifying Layer 2 Connectivity” section.\
Step 3 Verify the configuration for your end devices (storage subsystems and servers).
Step 4 Verify end-to-end connectivity. See the “Verifying Layer 3 Connectivity” section.
This section highlights the tools that are commonly used to troubleshoot problems within your network. These tools are a subset of what you may use to troubleshoot your specific problem.
Each chapter in this guide may include additional tools and commands specific to the symptoms and possible problems covered in that chapter.
You should also have an accurate topology of your network to help isolate problem areas.
Issue the following commands and examine the outputs:
- show module
- show version
- show running-config
- show logging log
- show interfaces brief
- show vlan
- show accounting log
- show tech support svs
Note To issue commands with the internal keyword, you must log in with a network-admin role.
Answer the following questions to verify ports:
- Are you using the correct media copper or optical; fiber type.
- Is the media broken or damaged?
- Are you checking a virtual Ethernet port? If so, then use the show interface brief command. The status should be up.
- Are you checking a physical Ethernet port? If so, you need to check it by looking at the server, or by looking at an upstream switch.
- Check if the network adapters of the VSM VM are assigned the right port groups and if all of them are connected from the vSphere Client.
Verifying Layer 2 Connectivity
Answer the following questions to verify layer 2 connectivity:
- Are the necessary interfaces in the same VLANs?
- Are all ports in a port channel configured the same for speed, duplex, trunk mode?
Use the show vlan brief command. The status should be up.
Use the show port-profile command to check a port profile configuration?
Use the show interface-brief command to check the status of a virtual Ethernet port or a physical Ethernet port.
Verifying Layer 3 Connectivity
Answer the following questions to verify layer 3 connectivity:
- Have you configured a gateway of last resort?
- Are any IP access lists, filters, or route maps blocking route updates?
Use the ping or trace commands to verify connectivity. See the following for more information:
Overview of Symptoms
The symptom-based troubleshooting approach provides multiple ways to diagnose and resolve problems. By using multiple entry points with links to solutions, this guide best serves users who may have identical problems that are perceived by different indicators. Search this guide in PDF form, use the index, or rely on the symptoms and diagnostics listed in each chapter as entry points to access necessary information in an efficient manner.
Using a given a set of observable symptoms on a network, it is important to be able to diagnose and correct software configuration issues and inoperable hardware components so that the problems are resolved with minimal disruption to the network. Those problems and corrective actions include the following:
- Identify key Cisco Nexus 1000V troubleshooting tools.
- Obtain and analyze protocol traces using SPAN or Ethanalyzer on the CLI.
- Identify or rule out physical port issues.
- Identify or rule out switch module issues.
- Diagnose and correct layer 2 issues.
- Diagnose and correct layer 3 issues.
- Obtain core dumps and other diagnostic data for use by the TAC.
- Recover from switch upgrade failures.
The system software sends the syslog (system) messages to the console (and, optionally, to a logging server on another system) during operation. Not all messages indicate a problem with your system. Some messages are purely informational, while others might help diagnose problems with links, internal hardware, or the system software.
This section contains the following topics:
System Message Text
Message-text is a text string that describes the condition. This portion of the message might contain detailed information about the event, including terminal port numbers, network addresses, or addresses that correspond to locations in the system memory address space. Because the information in these variable fields changes from message to message, it is represented here by short strings enclosed in square brackets. A decimal number, for example, is represented as [dec].
2009 Apr 29 12:35:51 n1000v %KERN-1-SYSTEM_MSG: stun_set_domain_id : Setting domain ID (1024) - kernel
Use this string to find the matching system message in the Cisco NX-OS System Messages Reference System Messages Reference.
Each system message is followed by an explanation and recommended action. The action may be as simple as “No action required.” It may involve a fix or a recommendation to contact technical support as shown in the following example:
Error Message 2009 Apr 29 14:57:23 n1000v %MODULE-5-MOD_OK: Module 3 is online (serial:)
Explanation VEM module inserted successfully on slot 3.
Recommended Action None. This is an information message. Use "show module" to verify the module in slot 3.
Syslog Server Implementation
The syslog facility allows the Cisco Nexus 1000V device to send a copy of the message log to a host for more permanent storage. This can be useful if the logs need to be examined over a long period of time or when the Cisco Nexus 1000V device is not accessible.
This example demonstrates how to configure a Cisco Nexus 1000V device to use the syslog facility on a Solaris platform. Although a Solaris host is being used, syslog configuration on all UNIX and Linux systems is very similar.
Syslog uses the concept of a facility to determine how it should be handled on the syslog server (the Solaris system in this example), and the message severity. Therefore, different message severities can be handled differently by the syslog server. They could be logged to different files or e-mailed to a particular user. Specifying a severity determines that all messages of that level and greater severity (lower number) will be acted upon.
Note The Cisco Nexus 1000V messages should be logged to a different file from the standard syslog file so that they cannot be confused with other non-Cisco syslog messages. The logfile should not be located on the / file system, to prevent log messages from filling up the / file system.
Syslog Client: switch1
Syslog Server: 172.22.36.211 (Solaris)
Syslog facility: local1
Syslog severity: notifications (level 5, the default)
File to log Cisco Nexus 1000V messages to: /var/adm/nxos_logs
To configure a syslog server, follow these steps:
Step 1 Configure the Cisco Nexus 1000V:
Enter configuration commands, one per line. End with CNTL/Z.
n1000v(config)# logging server 192.0.2.1 6 facility local1
To display the configuration:
n1000v# show logging server
server severity: notifications
Step 2 Configure the syslog server:
a. Modify /etc/syslog.conf to handle local1 messages. For Solaris, there needs to be at least one tab between the facility.severity and the action (/var/adm/nxos_logs).
#Below is for the NX-OS logging
b. Create the log file.
c. Restart syslog.
# /etc/init.d/syslog stop
# /etc/init.d/syslog start
d. Verify syslog started.
root 23508 1 0 11:01:41 ? 0:00 /usr/sbin/syslogd
Step 3 Test the syslog server by creating an event in Cisco Nexus 1000V. In this case, port e1/2 was bounced and the following was listed on the syslog server. Notice that the IP address of the switch is listed in brackets.
# tail -f /var/adm/nxos_logs
Sep 17 11:07:41 [172.22.36.142.2.2] : 2004 Sep 17 11:17:29 pacific:
%PORT-5-IF_DOWN_INITIALIZING: %$VLAN 1%$ Interface e 1/2 is down (Initializing)
Sep 17 11:07:49 [172.22.36.142.2.2] : 2004 Sep 17 11:17:36 pacific: %PORT-5-IF_UP:
%$VLAN 1%$ Interface e 1/2 is up in mode access
Sep 17 11:07:51 [172.22.36.142.2.2] : 2004 Sep 17 11:17:39 pacific:
%VSHD-5-VSHD_SYSLOG_CONFIG_I: Configuring console from pts/0
Troubleshooting with Logs
Cisco Nexus 1000V generates many types of system messages on the switch and sends them to a syslog server. These messages can be viewed to determine what events may have led up to the current problem condition you are facing.
Use the following commands to access and view logs in Cisco Nexus 1000V:
console Show console logging configuration
info Show logging configuration
internal syslog syslog internal information
last Show last few lines of logfile
level Show facility logging configuration
logfile Show contents of logfile
loopback Show logging loopback configuration
module Show module logging configuration
monitor Show monitor logging configuration
pending server address pending configuration
pending-diff server address pending configuration diff
server Show server logging configuration
session Show logging session status
status Show logging status
timestamp Show logging timestamp configuration
| Pipe command output to filter
Example 1-1 shows an example of the show logging command output.
Example 1-1 show logging Command
n1000v# show logging server
server severity: critical
Cisco Support Communities
For additional information, visit one of the following support communities:
Contacting Cisco or VMware Customer Support
If you are unable to solve a problem after using the troubleshooting suggestions in this guide, contact a customer service representative for assistance and further instructions. Before you call, have the following information ready to help your service provider assist you as quickly as possible:
- Version of the Nexus 1000V software that you are running
- Version of the ESX and vCenter Server software that you are running
- Contact phone number.
- Brief description of the problem
- Brief explanation of the steps you have already taken to isolate and resolve the problem
If you purchased the Cisco Nexus 1000V and support contract from Cisco, contact Cisco for Nexus 1000V support. Cisco provides L1, L2, and L3 support.
If you purchased the Cisco Nexus 1000V and an SNS through VMware, you should call VMware for Nexus 1000V support. VMware provides L1 and L2 support. Cisco provides L3 support.
After you have collected this information, see the “Obtaining Documentation and Submitting a Service Request” section.
For more information on steps to take before calling Technical Support, see the “Gathering Information for Technical Support” section.