IP Addresses and Services Configuration Guide for Cisco 8000 Series Routers, IOS XR Releases

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IP Addresses and Services Configuration Guide for Cisco 8000 Series Routers, IOS XR Releases

Network diagnostic services

Updated: August 12, 2026

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Explains how ping, traceroute, enhanced ICMP diagnostics, and ICMP probes test reachability, expose packet paths, and report interface or neighbor status, with tasks for running and configuring each utility.

Network diagnostic services are utilities that

  • test whether one or more destinations respond

  • identify Layer 3 hops and routing failures, and

  • provide interface, next-hop, and neighbor details for troubleshooting.

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

Network Connectivity Tools: Ping and Traceroute

 Release 25.4.1

Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*)

*This feature is now supported on:

  • 8011-32Y8L2H2FH

  • 8011-12G12X4Y-A/D

Network Connectivity Tools: Ping and Traceroute

Release 25.1.1

Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*)

*This feature is supported on Cisco 8011-4G24Y4H-I routers.

Network Connectivity Tools: Ping and Traceroute

Release 24.4.1

Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100, K100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*)

The ping command can be used to verify connectivity between devices, the traceroute command can be used to discover the paths packets take to a remote destination and where routing breaks down.

*This feature is now supported on:

  • 8212-48FH-M

  • 8711-32FH-M

  • 8712-MOD-M

  • 88-LC1-36EH

  • 88-LC1-12TH24FH-E

  • 88-LC1-52Y8H-EM

Ping utilities

A ping utility is a network diagnostic tool that

  • exchanges Internet Control Message Protocol (ICMP) echo request and echo reply messages with a destination

  • measures the time required to receive each reply, and

  • supports basic, extended, and bulk reachability tests.

A basic ping tests a destination by using the outgoing interface address as the packet source.

An extended ping lets you select the source address, timeout, datagram size, and other parameters.

A bulk ping accepts multiple destinations directly from the CLI and supports IPv4 destinations only.

How ping verifies reachability

Ping uses Internet Control Message Protocol (ICMP) echo messages to evaluate path reliability, path delay, and destination availability.

Summary

The process uses these messages.

  • ICMP echo request: The source sends a query to the destination.

  • ICMP echo reply: The destination returns a response to the source.

Workflow

These stages describe how ping verifies reachability.

  1. The source sends an ICMP echo request to the specified address and starts the reply timer.

  2. The request traverses the network to the destination. A basic ping uses the outgoing interface address as its source unless you select another source with extended ping.

  3. The destination returns an ICMP echo reply. The test succeeds when the reply reaches the source within the configured timeout.

Result

The output reports the success rate and can report round-trip timing statistics.

Extended ping connectivity tests

An extended ping connectivity test is a diagnostic method that

  • uses a selected router interface address as the source of an ICMP echo request

  • tests the forward and return routes between two specified interfaces, and

  • isolates routing problems before you troubleshoot the attached hosts.

A basic ping normally uses the address of the outgoing interface as its source. Extended ping lets you select the source address that represents the path you want to test.

Extended ping connectivity scenario

The example tests connectivity from the HundredGigE interface on Router A at 192.0.2.2 to the interface on Router B at 192.0.2.1.

Figure 1. Extended ping connectivity path

Router A and Router B connected through Router C, with Host 1 and Host 2 attached to the edge routers.

A successful extended ping confirms these routing conditions.

  • Router A has a route to the Router B interface.

  • Router B has a return route to the Router A source interface.

  • The intermediate routers can forward traffic between the two interface subnets.

Failed test interpretation

A failed extended ping can indicate a missing route at any router in the path.

Table 2. Potential routing failures

Router

Potential missing route

Router A

A route to the Router B interface subnet or to the subnet between Router C and Router B.

Router B

A route to the Router A interface subnet or to the subnet between Router C and Router A.

Router C

A route to the Ethernet segment attached to Router A or Router B.

Correct the routing problem before Host 1 pings Host 2. If the hosts still cannot communicate after the extended ping succeeds, verify the default gateway on each host.

Check network connectivity with ping

Use ping to confirm that the destination responds and that return routing is available.

An extended ping can test connectivity between specific router interfaces instead of using the outgoing interface address automatically.

Procedure

  1. Run a basic ping to the destination.

    Example:

    Router# ping 192.0.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5)

  2. Run an interactive ping when you must specify additional parameters.

    Example:

    Router# ping
Protocol [ipv4]: ipv4
Target IP address: 192.0.2.1
Repeat count [5]: 5
Datagram size [100]: 36
Timeout in seconds [2]: 1
Extended commands? [no]: yes
Source address or interface: 192.0.2.2

  3. Review the success rate and round-trip timing values.

A successful test confirms reachability between the selected source and destination addresses.

Check connectivity to multiple destinations

Use bulk ping when you need to test several IPv4 destinations.

Before you begin

Prepare the IPv4 destination addresses. The bulk option supports IPv4 destinations only.

Procedure

  1. Start a bulk IPv4 ping that accepts destinations from the CLI.

    Example:

    Router# ping bulk ipv4 input cli batch

  2. Enter one destination per line, and then press Ctrl-D.

    Example:

    1: 192.0.2.1
2: 198.51.100.1
3: 203.0.113.1

  3. Respond to the prompts for each destination and review each success rate.

    Example:

    Starting pings...
Target IP address: 192.0.2.1
Repeat count [5]: 5
Datagram size [100]: 1
% A decimal number between 36 and 18024.
Datagram size [100]: 1
% A decimal number between 36 and 18024.
Datagram size [100]: 1000
Timeout in seconds [2]: 1
Interval in milliseconds [10]: 10
Extended commands? [no]: no
Sweep range of sizes? [no]: 
Type escape sequence to abort.
Sending 5, 1000-byte ICMP Echos to 192.0.2.1, vrf is default, timeout is 1 seconds:
!!!!!
Success rate is 100 percent (5/5),
Target IP address: 198.51.100.1
Repeat count [5]: 
Datagram size [100]: 
Timeout in seconds [2]: 
Interval in milliseconds [10]: 
Extended commands? [no]: 
Sweep range of sizes? [no]: 
Sending 5, 100-byte ICMP Echos to 192.0.2.1, vrf is default, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5),
Target IP address:  203.0.113.1
Repeat count [5]: 4
Datagram size [100]: 100
Timeout in seconds [2]: 1
Interval in milliseconds [10]: 10
Extended commands? [no]: no
Sweep range of sizes? [no]: no
Sending 4, 100-byte ICMP Echos to 192.0.2.1, vrf is default, timeout is 1 seconds:
!!!!!
Success rate is 100 percent (4/4),

The router runs the configured ping test for every supplied IPv4 destination.

Traceroute utilities

A traceroute utility is a network diagnostic tool that

  • identifies the path that packets take toward a remote destination

  • displays the responding Layer 3 devices in hop order, and

  • helps locate the point at which routing stops.

A basic traceroute uses default probe, timeout, TTL, port, and display settings.

An interactive traceroute lets you select the source address, timeout, probe count, TTL range, UDP port, and display options.

How traceroute discovers packet paths

Traceroute records the source of each Internet Control Message Protocol (ICMP) time-exceeded message to identify the path that a packet takes toward a remote destination.

Summary

The process relies on these fields and messages.

  • TTL: Limits how many Layer 3 hops process a datagram.

  • ICMP time-exceeded message: Identifies an intermediate hop.

  • ICMP port-unreachable message: Indicates that the datagram reached the destination.

Workflow

These stages describe how traceroute discovers a packet path.

  1. Traceroute sends a UDP datagram with a TTL value of 1. The first router discards the datagram and returns an ICMP time-exceeded message.

  2. Traceroute increases the TTL for each successive set of probes. Each router that reduces the TTL to zero identifies itself in an ICMP response.

  3. The destination receives a datagram addressed to an unused high-numbered UDP port and returns an ICMP port-unreachable message.

Result

The output lists the discovered Layer 3 hops in path order.

Trace packet routes

Use traceroute to identify the hops toward a destination and the point at which routing stops.

Procedure

  1. Trace the route to the destination.

    Example:

    Router# traceroute 198.51.100.1
Type escape sequence to abort.
Tracing the route to 198.51.100.1
1 192.0.2.1 39 msec * 3 msec

  2. Run interactive traceroute when you must specify additional parameters.

    Example:

    Router# traceroute
Protocol [ipv4]: ipv4
Target IP address: 198.51.100.1
Source address: 192.0.2.1
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]: 

Type escape sequence to abort.
Tracing the route to 198.51.100.1
 1  192.0.2.1.1 3 msec  *  3 msec

  3. Review the hop addresses and response times to locate a routing failure.

The output identifies each responding hop between the source and destination.

Enhanced ICMP diagnostics for traceroute

Enhanced ICMP diagnostics are traceroute extensions that

  • add incoming and outgoing interface names, addresses, and MTU values to ICMP error messages

  • identify the next-hop address at each supported hop, and

  • improve path analysis when interface addressing or topology makes basic traceroute output insufficient.

The implementation complies with RFC 5837 and shares its permitted-remote-address configuration with the RFC 8335 ICMP probe utility.

Table 3. Feature History Table

Feature Name

Release Information

Feature Description

Enhanced ICMP error messages for traceroute

Release 25.4.1

Introduced in this release on: Fixed Systems (8200 [ASIC: Q100, Q200, P100], 8700 [ASIC: P100, K100], 8010 [ASIC: A100]); Centralized Systems (8600 [ASIC:Q200]) ; Modular Systems (8800 [LC ASIC: Q100, Q200, P100])

You now get detailed insights into each step of the network path. Building on the existing traceroute utility, this feature adds more diagnostic information to ICMP error messages. At each hop, the router shows not only the IP address, but also the incoming and outgoing interfaces and the next hop IP address. This makes it easier to find and fix network issues.

This feature introduces these changes:

CLIs:

YANG Data Model:

  • Cisco-IOS-XR-um-ip-icmp-cfg

  • Cisco-IOS-XR-traceroute-act

(see GitHub, YANG Data Models Navigator)

Restriction for enhanced ICMP diagnostics for traceroute

SRv6 does not support enhanced ICMP messages for traceroute.

Benefits of enhanced ICMP diagnostics for traceroute

Enhanced ICMP error messages for traceroute provide several benefits.

  • These messages improve visibility into network paths, which allows network operators to diagnose issues more effectively.

  • Enhanced ICMP error messages enable identification of specific interfaces and their characteristics at each hop along the network path.

  • They help to solve limitations encountered in complex environments, such as those involving unnumbered interfaces or networks that use only loopback IPv4 addresses.

  • These messages offer a clearer understanding of how packets traverse the network, supporting more accurate network analysis and troubleshooting.

Enable enhanced ICMP diagnostics for traceroute

Use this procedure to provide extended diagnostic information in ICMP error messages, improving the effectiveness of traceroute for network troubleshooting.

By default, extended ICMP diagnostics are disabled. You must configure which remote addresses or prefixes are permitted to receive enhanced diagnostics. Optionally, enable diagnostics for MPLS traffic or use a wildcard to cover all destinations. This configuration is shared with the ICMP PROBE Utility (RFC 8335). For information on how to configure ICMP PROBE utility, see ICMP probe utilities. The implementation of enhanced ICMP error messages for traceroute complies with RFC 5837.

Before you begin

  • Identify the IP address prefixes (IPv4 or IPv6) for which you want to enable extended diagnostics (up to 1024 prefixes are supported).

  • If your network uses MPLS, determine whether extended diagnostics for MPLS traffic should also be enabled.

Procedure

  1. Enable extended ICMP diagnostics for the desired VRF and IP address or prefix.

    Example:

    Router# configure
Router(config)# icmp ipv4 vrf default extended-diagnostics permitted-remote-address 192.168.0.0/16
Router(config-icmp-vrf-diag)# commit

  2. Enable extended diagnostics for MPLS traffic.

    Example:

    Router# configure
Router(config)# icmp ipv4 mpls
Router(config-icmp-mpls)# extended-diagnostics
Router(config-icmp-mpls-diag)# commit

    When MPLS support is enabled, incoming MPLS packets are checked against the list of permitted remote prefixes for the default VRF.

    The same configuration can also be repeated in IPv6.

  3. Repeat step 1 and 2 on each intermediate router along the traceroute path.

    This configuration should be applied to the routers that are expected to generate the enhanced ICMP error messages.

  4. Verify the configuration.

    Example:

    Router# show running-config icmp ipv4 vrf extended-diagnostics

  5. Display enhanced diagnostic information, if configured and available.

    Example:

    Router# traceroute ipv4 192.168.1.10 source Loopback0 extended
ype escape sequence to abort.
Tracing the route to 192.168.1.10

 1  192.168.1.1  16 msec  15 msec  14 msec 
     incoming GigabitEthernet0/0/0/1:
       Address: 192.168.1.1
       MTU: 1500
     outgoing GigabitEthernet0/0/0/2:
       Address: 192.168.1.2
       MTU: 1500
     next hop:
       Address: 192.168.1.10

 2  192.168.1.10  21 msec 
     incoming GigabitEthernet0/0/0/2:
       Address: 192.168.1.10
       MTU: 1500

The routers include extended diagnostic information in ICMP error messages for specified remote address prefixes. Enhanced diagnostics are displayed in traceroute output for supported destinations.

What to do next

Review traceroute output to confirm that diagnostic information is present. Adjust permitted prefixes or enable MPLS diagnostics on additional routers as needed.

ICMP probe utilities

An ICMP probe utility is a diagnostic tool that

  • queries the operational status of local interfaces or directly connected remote neighbors

  • reports interface activity and IPv4 or IPv6 reachability through a proxy, and

  • supports troubleshooting when direct bidirectional connectivity is unavailable.

The utility supports same-family and cross-address-family probes and can expose partial-path, asymmetric-routing, and interface-specific problems that a traditional ping might not identify.

Table 4. Feature History Table

Feature Name

Release Information

Feature Description

ICMP probe utility

Release 25.4.1

Introduced in this release on: Fixed Systems (8200 [ASIC: Q100, Q200, P100], 8700 [ASIC: P100, K100], 8010 [ASIC: A100]); Centralized Systems (8600 [ASIC:Q200]) ; Modular Systems (8800 [LC ASIC: Q100, Q200, P100])

This feature introduces a new network diagnostic tool called probe, similar to ping but with enhanced capabilities. It allows users to query the operational status of local interfaces or directly connected remote neighbors, providing details like probe can report whether the interface is active, and whether IPv4 and IPv6 are running. probe operates through a proxy device, making it suitable for troubleshooting scenarios where direct bidirectional connectivity to the probed interface is not available.

This feature introduces these changes:

CLI:

ICMP probe utilities expand upon the traditional ping diagnostic tool by delivering enhanced information about network interfaces and neighbors. First introduced in Release 25.4.1, these utilities allow network administrators to diagnose connectivity and status even in complex environments where direct access may not be possible.

Benefits of ICMP probe utilities

ICMP probe utilities provide these diagnostic benefits.

  • The utilities support IPv4 and IPv6 operations, including cross-address-family tests that use an IPv4 probe to assess an IPv6 destination.

  • The utilities report the state and reachability of each tested interface or neighbor.

  • The utilities identify asymmetric-routing, partial-path, and interface-specific problems that a traditional ping might not detect.

  • The utilities summarize successful and failed probe attempts so that you can isolate connectivity problems quickly.

  • The utilities let you specify source and destination addresses for complex or multihomed networks.

Configure the ICMP probe utility

Configure ICMP probes to diagnose interface or directly connected neighbor reachability.

The probe feature is disabled by default and reuses the RFC 5837 permitted-remote-address configuration. Probe replies are sent only when the source matches that list.

Procedure

  1. Define a permitted remote prefix for the required VRF.

    Example:

    Router# configure
Router(config)# icmp ipv4 vrf default extended-diagnostics permitted-remote-address 192.168.1.0/24
Router(config-icmp-vrf-diag)# commit

    You can configure up to 1,024 IPv4 and IPv6 prefixes.

  2. Run a local probe for an interface on the proxy device.

    Example:

    Router# probe 192.168.1.10 source Loopback0 by-name BVI1

  3. Run a remote probe to test a directly connected neighbor.

    Example:

    Router# probe 2001:db8::1 source GigabitEthernet0/0/0/0 by-remote-address fe80::1

The device reports interface activity or neighbor reachability for each permitted probe.