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How to troubleshoot IP Fabric VM

In the event of a VM network connection problem, DNS issues, network devices connectivity issue, IP Fabric CLI is a useful helper.

CLI can be also used to access system and application logs as well as snapshot files.

Checking The Network Interface Settings

Warning

When you log in through a VM console or SSH, network settings are displayed. This content is static, generated when VM boots! When DHCP is used, an IP address can change in some cases.

VM IP

To display actual IP address use command:

ip addr show

Default gateway and other routes (if configured) can be check as follows:

ip r

Checking DNS

DNS can be checked using the dig or nslookup command.

For example, let’s check A record and PTR (reverse) record of some device using dig.

For A record check ANSWER which contains requested IP address. Also SERVER section below is important as it tell us what DNS server answered our DNS query.

DNS A record

For PTR record check ANSWER which contains requested domain name.

DNS PTR record

If you prefer nslookup you can achieve the same results.

nslookup

Testing Connectivity To a Network Device

The very basic test is ping or traceroute.

Warning

Please bear in mind that ICMP packets used by ping and traceroute can be blocked by ACL or firewall. It does not mean that a device cannot be reached using SSH or telnet.

To make sure that the network device is available from IP Fabric VM, you can use the telnet and ssh client from the command line.

For SSH use:

ssh userName@device-IP-or-Hostname

For telnet use:

telnet device-IP-or-Hostname

Since version 5.0, there is also a new tool called ipf-connection-tester for connecting to network devices using the same library that we use in discovery (if ssh or telnet works with the default Linux client, it does not automatically mean it will also work during the discovery as system clients are not used).

To test SSH connectivity, use:

ipf-connection-tester ssh userName@device-IP-or-Hostname

If you are getting timeouts, it is possible to increase the default timeout options:

Options:
  -r, --ready-timeout <timeout>  seconds to wait till connection is ready (default: 30)
  -d, --data-timeout <timeout>   seconds to wait till data is received (default: 10)

For example:

ipf-connection-tester ssh userName@device-IP-or-Hostname -r 60 -d 20

For telnet, simply change ssh to telnet:

ipf-connection-tester telnet userName@device-IP-or-Hostname

Timeout options are the same. However, the telnet connection tester is much less verbose than the SSH one, so for both security and verbosity, prefer SSH whenever possible.

If you wish to run ipf-connection-tester from your own automation script, here are possible return values:

  • 0 – Connection success
  • 1 – Missing or invalid command line arguments
  • 2 – Connection failed

Reboot And Shutdown

IP Fabric VM can be also rebooted or shutdown using CLI.

For VM reboot just use reboot command without any parameters.

For VM shutdown use shutdown command without any parameters.