Application Hosting Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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Application Hosting Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Packet I/O infrastructure reachability

Updated: June 12, 2026

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Describes how IOS XR interfaces are exposed to the Linux kernel and how the global virtual routing and forwarding (VRF) namespace reaches IOS XR routing through the to_xr interface.

Packet I/O infrastructure reachability is a networking capability that

  • exposes IOS XR interfaces as Linux kernel interfaces with inherited IP address, MTU, and MAC address values

  • enables access to the global virtual routing and forwarding (VRF) namespace through the bash command in the Linux shell, and

  • connects Linux routing to the IOS XR default VRF using the to_xr interface.

Accessing the global VRF network namespace through the bash command reflects the IOS XR default VRF in the kernel, enabling default reachability based on IOS XR routing and Packet I/O infrastructure.

Feature history

Table 1. Feature history table

Feature name

Release information

Description

Virtual IP address in the Linux networking stack

 Release 25.4.1

Introduced in this release on fixed systems (8010 [ASIC: A100]) for select variants.

This feature is supported on:

  • 8011-32Y8L2H2FH

  • 8011-12G12X4Y-A/D

Virtual IP address in the Linux networking stack

Release 25.1.1

Introduced in this release on fixed systems (8700 [ASIC: K100], 8010 [ASIC: A100]) for select variants.

This feature is supported on:

  • 8712-MOD-M

  • 8011-4G24Y4H-I

Virtual IP address in the Linux networking stack

Release 24.4.1

Introduced in this release on fixed systems (8200 [ASIC: P100], 8700 [ASIC: P100]) and modular systems (8800 [LC ASIC: P100]) for select variants.

This feature is supported on:

  • 8212-48FH-M

  • 8711-32FH-M

  • 88-LC1-36EH

  • 88-LC1-12TH24FH-E

  • 88-LC1-52Y8H-EM

Virtual IP address in the Linux networking stack

Release 7.5.2

Virtual IP addresses allow a single IP address to connect to the current active route processor (RP) after an RP switchover event. This functionality enables the network stack to support virtual IP addresses for third-party applications and IOS XR applications using the Linux networking stack.

These commands are modified:

Automatic synchronization of secondary IPv4 addresses from IOS XR to Linux operating system

 Release 25.4.1

Introduced in this release on fixed systems (8010 [ASIC: A100]) for select variants.

This feature is supported on:

  • 8011-32Y8L2H2FH

  • 8011-12G12X4Y-A/D

Automatic synchronization of secondary IPv4 addresses from IOS XR to Linux operating system

Release 25.1.1

Introduced in this release on fixed systems (8700 [ASIC: K100], 8010 [ASIC: A100]) for select variants.

This feature is supported on:

  • 8712-MOD-M

  • 8011-4G24Y4H-I

Automatic synchronization of secondary IPv4 addresses from IOS XR to Linux operating system

Release 24.4.1

Introduced in this release on fixed systems (8200 [ASIC: P100], 8700 [ASIC: P100]) and modular systems (8800 [LC ASIC: P100]) for select variants.

This feature is supported on:

  • 8212-48FH-M

  • 8711-32FH-M

  • 88-LC1-36EH

  • 88-LC1-12TH24FH-E

  • 88-LC1-52Y8H-EM

Automatic synchronization of secondary IPv6 addresses from IOS XR to Linux operating system

Release 7.11.1

Configured interface secondary IPv6 addresses on IOS XR are automatically synchronized to the Linux operating system. Third-party applications can use secondary IPv6 addresses without manual intervention.

Automatic synchronization of secondary IPv4 addresses from IOS XR to Linux operating system

Release 7.5.3

Configured interface secondary IPv4 addresses on IOS XR are automatically synchronized to the Linux operating system. Third-party applications can use secondary IPv4 addresses without manual intervention.

Verify the reachability of IOS XR and Packet I/O infrastructure

Use this task to confirm that IOS XR interfaces are visible from the Linux networking stack and that the Packet I/O infrastructure delivers default reachability through IOS XR routing.

Before you begin

  • Obtain access credentials for both the IOS XR console and Linux shell.

  • Confirm SSH connectivity from your Linux host to the IOS XR router.

Follow these steps to verify reachability:

Procedure

1.

Access the IOS XR console from your Linux host using SSH.

Example:

cisco@host:~$ ssh root@192.168.122.188
root@192.168.122.188's password:
Router#
2.

View Ethernet interfaces on IOS XR to confirm their status.

Example:

Router#show ip interface brief
Interface                      IP-Address      Status          Protocol Vrf-Name
FourHundredGigE0/0/0/0         unassigned      Shutdown        Down     default
...
HundredGigE0/0/0/24            10.1.1.10       Up              Up       default
MgmtEth0/RP0/CPU0/0            192.168.122.22  Up              Up       default
Note

Use the ip addr show or ip link show commands to view all corresponding interfaces in Linux. Interfaces in the IOS XR admin-down state also show a Down state in the Linux kernel.
3.

Check the IP and MAC addresses of interfaces in the Up state. In this example, HundredGigE0/0/0/24 and MgmtEth0/RP0/CPU0/0 are in the Up state.

Example:

Router#show interfaces HundredGigE0/0/0/24
HundredGigE0/0/0/24 is up, line protocol is up
  Hardware is HundredGigE0/0/0/24, address is 0000.5e00.5301 (bia 0000.5e00.5301)
  Internet address is 10.1.1.1/24
  MTU 1514 bytes, BW 1000000 Kbit (Max: 1000000 Kbit)
4.

Verify that the bash command runs in the global VRF to view network interfaces.

Example:

Router#bash -c ifconfig
Hu0_0_0_24  Link encap:Ethernet  HWaddr 00:00:5e:00:53:01
            inet addr:10.1.1.10  Bcast:0.0.0.0  Mask:255.255.255.0
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
to_xr       Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
            UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1

The to_xr interface indicates access to the global VRF.
5.

Access the Linux shell.

Example:

Router#bash
[ios:~]$
6.

(Optional) View the IP routes associated with the to_xr interface in Linux.

Example:

[ios:~]$ip route
default dev to_xr scope link metric 2048
192.0.2.0/24 dev Mg0_RP0_CPU0_0 proto kernel scope link src 192.0.2.41
10.1.1.0/24  dev Hu0_0_0_0     proto kernel scope link src 10.1.1.1
172.17.0.0/16 dev docker0      proto kernel scope link src 172.17.0.1 linkdown
Note

You can enter the global VRF directly after logging in to IOS XR using the run ip netns exec vrf-default bash command.

IOS XR interfaces appear in the Linux kernel, the global VRF is accessible from the bash shell, and the to_xr interface is present in the routing table, confirming that Packet I/O infrastructure is operational.