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How to use the Probe command

 
Summary

Learn how to configure and use the Probe command.

Benefits of the Probe command

The Probe command helps to capture the interface details such as system statistics, and interface state (active/inactive), irrespective of whether the network family address configured is IPv4 or IPv6 on the probed interfaces.

What is the Probe Command?

RFC 8335, PROBE: A Utility for Probing Interfaces, describes the Probe utility. Probe is a network diagnostic tool similar to Ping that can be used to query the status of a probed interface on a node. The Probe command require bidirectional connectivity between the probing interface and the proxy interface. The proxy interface can reside on the same node as the probed interface, or it can reside on a node to which the probed interface is directly connected. Probe uses ICMP Extended Echo/Reply messages for communication between the probing interface and the proxy interface. The Probe command is used to probe the details of the interfaces on the probed node that is directly connected to the proxy, where the proxy learns the details from the ARP or NDP entries of those interfaces. This utility helps in scenarios where bidirectional connectivity between the probing and probed interfaces is lacking. For example, if the probed interface is an unnumbered interface or if the probed interface is in a different network family.

The following figure shows R0 as the probing node, R1 as the proxy node, and R2 as the probed node:

Figure 1: Probing, Proxy, and Probed Nodes
Probing, Proxy, and Probed Nodes

Enabling the Probe command

To enable the probe command, configure the extended-echo configuration statement at the [edit system] hierarchy level on the proxy node and the probed node.

Note

You do not need to enable the extended-echo configuration statement on the probing node.

Using the Probe command

You can probe using three different options:

  • By using IP address.

  • By using interface names.

  • By using the interface index.

The following examples shows how to use the probe command. Consider R0 as the probing node, R1 as the proxy node, and R2 as the probed node and change the details of the interfaces and IP addresses to match your network configuration.

Purpose

Use case 1: Probing when the proxy interface and the probed interface reside on two different nodes (proxy node (R1) and the probed node (R2)).

Query for the status of the probed IP address through the proxy IP address.

Action

From operational mode, probe for the status of the IP address 198.52.102.36 of the probed node (R2) using the by-address option with the proxy IP address 198.52.100.1 of the proxy node (R1). Count 1 indicates that the number of probe requests sent is 1.

user@R0>probe 198.52.100.1 by-address 198.52.102.36 count 1

Meaning

The proxy IP address, 198.52.100.1 displays the status of the probed IP address, 198.52.102.36. The output is verified with the following probe packet statistics:

  • code=2 indicates that IP address is not configured on the probed interface.

  • state=0 indicates that at the time of probing, the state of the IPv6 or IPv4 node is reachable.

  • active=0 indicates that the probed node is inactive as the IPv4 or IPv6 address is not available or configured on the probed node. That is, the probed IP address, 198.52.102.36 is not configured on the probed node (R2).

  • IPv4=0 and IPv6=0 indicates that the IPv4 and IPv6 addresses are not configured.

  • time=milliseconds ms indicates the time taken to receive the reply after the request is transmitted.

  • ttl is the time to live value (maximum IPv6 hop-limit-value).

Purpose

Use Case 2: Probing when proxy node and the probed node are the same.

Query for the status of the probed IP address through the proxy IP address (here, the probed IP address and the proxy IP address are configured on the same node, R1)

Action

From operational mode, probe for the status of the probed IP address 198.52.102.2 using the by-address option with the proxy IP address 198.52.100.1 at the proxy node (R1). Count 1 indicates that the number of probe requests sent is 1.

user@R0>probe 198.52.100.1 by-address 198.52.102.2 count 1

Meaning

The proxy IP address, 198.52.100.1 displays the status of the probed IP address, 198.52.102.2. The output is verified with the following probe packet statistics:

  • code=0 indicates that the connection is successfully established and has no error.

  • state=0 indicates that at the time of probing the state of the IPv6 or IPv4 node is reserved.

  • active=1 indicates that the probed node is active and either the IPv4 or IPv6 addresses or both are configured and available on the probed node.

  • IPv4=1 and IPv6=1 indicates that the IPv4 and IPv6 addresses are configured and available on the probed node.

  • time=milliseconds ms indicates the time taken to receive the reply after the request is transmitted.

  • ttl is the time to live value (maximum IPv6 hop-limit-value).

Purpose

Query for the status of the IPv4 or IPv6 address using the interface index of the probed interface.

Action

From operational mode, probe for the status of the IPv4 or IPv6 address using the by-index option to specify the interface index of the probed interface.

user@R0>probe 198.52.100.1 by-index 1037

Meaning

The proxy IP address, 198.52.100.1 displays the status of the probed interface using the interface index-id, 1037. The output is verified with the following probe packet statistics:

  • code=0 indicates that the connection is successfully established and has no error.

  • state=0 indicates the reserved state of the packet and at the time of probing the state of the IPv6 or IPv4 node is reachable.

  • active=1 indicates that the probed node is active and either the IPv4 or the IPv6 address is available.

  • IPv4=1 indicates that the IPv4 address is configured and available. IPv6=0 indicates that the IPv6 address is not configured.

  • time=milliseconds ms indicates the time taken to receive the reply after the request is transmitted.

  • ttl is the time to live value (maximum IPv6 hop-limit-value).

Purpose

Query the proxy interface for information about the remote interface that reside on the remote node using the remote address.

Action

From operational mode, probe for the status of the probed node and verify using the by-remote-address option with the IP address of a remote device. Count 1 indicates that the number of probe requests sent is 1.

user@R0>probe 198.52.100.1 by-remote-address 2001:65::2 count 1

Meaning

The proxy IP address, 198.52.100.1 displays the status of the probed node using the IP address, 2001:65::2 of the remote device. The by-remote-address option is used to determine the status of the remote interface only. The output is verified with the following probe packet statistics:

  • code=0 indicates that the connection is successfully established and has no error.

  • state=2 indicates the reachable state of the packet that is, the connection is established with a remote node where the IPv4 and the IPv6 address is not available.

  • active=0 indicates that the probed node is inactive.

  • IPv4=0 and IPv6=0 indicates that the IPv4 and the IPv6 addresses are not configured or available. Note that when you probe using the by-remote-address option, the IPv4 or the IPv6 address is not available.

  • time=milliseconds ms indicates the time taken to receive the reply after the request is transmitted.

  • ttl is the time to live value (maximum IPv6 hop-limit-value).

Purpose

Query for the status of the probed interface using the interface name.

Action

From operational mode, probe for the status of the probed interface using the interface name ge-1/2/1.1 and verify the output through the IP address of the proxy node 198.52.100.1. Count 1 indicates that the number of probe requests sent is 1.

user@R0>probe 198.52.100.1 by-name ge-1/2/1.1 count 1

Meaning

The proxy IP address, 198.52.100.1 displays the status of the device with reference to the interface ge-1/2/1.1 of the device on the probed node. The output is verified with the following probe packet statistics:

  • code=0 indicates that the connection is successfully established and has no error.

  • state=0 indicates the reserved state of the packet and the proxy is able to establish a connection with the probed node.

  • active=1 indicates that the probed node is active and either the IPv4 or the IPv6 address configured is available.

  • IPv4=1 indicates that the IPv4 address is configured and available. IPv6=0 indicates that the IPv6 address is not configured.

  • time=milliseconds ms indicates the time taken to receive the reply after the request is transmitted.

  • ttl is the time to live value (maximum IPv6 hop-limit-value).