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

Manage IOS XR interfaces through Linux

Updated: June 12, 2026

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Linux-managed interfaces allow standard Linux automation tools to configure and manage IOS XR interfaces, enabling IP address changes, MTU settings, and state management to propagate bidirectionally between Linux and IOS XR.

A Linux-managed interface is an IOS XR exposed XR interface (EXI) that is configured to accept management input from Linux rather than from the IOS XR configuration. Key characteristics include:

By default, all IOS XR interfaces are managed through IOS XR configuration (CLI or YANG models), with attributes such as IP address, MTU, and state inherited from the IOS XR configuration and interface state.
When an interface is set to Linux-managed mode, standard Linux automation tools on Linux servers can manage IOS XR interfaces directly, and configuration changes made from Linux propagate back to IOS XR.
Secondary IPv4 addresses cannot be managed from Linux; only primary addresses are supported in Linux-managed mode.

Linux-managed interface capabilities

Each network namespace in the Linux system contains a set of interfaces that map to IOS XR interfaces. When an interface is Linux-managed, you can:

Configure new IP addresses on the interface from Linux using the ip addr add command.
Configure a custom MTU using the ip link set mtu command, which propagates the change back to the IOS XR configuration.
Bring the interface up or down using ifconfig commands, with state changes reflected in IOS XR.

Configure an interface to be Linux-managed

Use this procedure to expose a router interface to Linux so that the interface is accessible for packet management, routing, and diagnostics from the IOS XR bash shell.

Procedure

	1.	Check the available exposed-interfaces in the system. Example: Router(config)#linux networking exposed-interfaces interface ? Bundle-Ether Aggregated Ethernet interface(s) \| short name is BE FiftyGigE FiftyGigabitEthernet/IEEE 802.3 interface(s) \| short name is Fi FortyGigE FortyGigabitEthernet/IEEE 802.3 interface(s) \| short name is Fo FourHundredGigE FourHundredGigabitEthernet/IEEE 802.3 interface(s) \| short name is FH GigabitEthernet GigabitEthernet/IEEE 802.3 interface(s) \| short name is Gi HundredGigE HundredGigabitEthernet/IEEE 802.3 interface(s) \| short name is Hu Loopback Loopback interface(s) \| short name is Lo MgmtEth Ethernet/IEEE 802.3 interface(s) \| short name is Mg TenGigE TenGigabitEthernet/IEEE 802.3 interface(s) \| short name is Te TwentyFiveGigE TwentyFiveGigabitEthernet/IEEE 802.3 interface(s) \| short name is TF TwoHundredGigE TwoHundredGigabitEthernet/IEEE 802.3 interface(s) \| short name is TH
	2.	Configure the interface to be managed by Linux. Example: The following example shows how to configure a HundredGigE interface to be managed by Linux: `Router#configure Router(config)#linux networking exposed-interfaces interface HundredGigE 0/0/0/24 linux-managed Router(config-exi-if)#commit`
	3.	View the interface details and the VRF. Example: The following example shows the information for HundredGigE interface: `Router#show run interface HundredGigE0/0/0/24 interface HundredGigE0/0/0/24 mtu 4110 vrf blue ipv4 mtu 4096 ipv4 address 10.1.1.10 255.255.255.0 ipv6 mtu 4096 ipv6 address fe80::7ae7:e8ff:fed3:20c0 link-local !`
	4.	Verify the configuration in XR. Example: The following example shows the configuration for HundredGigE interface: `Router#show running-config linux networking linux networking exposed-interfaces interface HundredGigE0/0/0/24 linux-managed ! ! !`
	5.	Verify the configuration from Linux. Example: The following example shows the configuration for HundredGigE interface: Router#bash Router:Aug 1 17:40:02.873 UTC: bash_cmd[67805]: %INFRA-INFRA_MSG-5-RUN_LOGIN : User vagrant logged into shell from vty0 [ios:~]$ip netns exec vrf-blue bash [ios:~]$ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) 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 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) [ios:~]$ifconfig -a Hu0_0_0_24 Link encap:Ethernet HWaddr 78:e7:e8:d3:20:c0 BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) 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 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

Configure a new IP address on a Linux-managed interface

Use this procedure to configure a new IP address on a Linux-managed interface from the Linux shell. Changes made from Linux are propagated automatically to the IOS XR configuration for the interface.

Before you begin

Before you begin, configure the interface as Linux-managed. For details, see Configure an interface to be Linux-managed.

Procedure

Configure the IP address on the interface from the Linux shell.

Example:

[ios:~]$ip addr add 10.1.1.10/24 dev Hu0_0_0_24
[ios:~]$Router:Aug 1 17:41:11.546 UTC: xlncd[253]: %MGBL-CONFIG-6-DB_COMMIT : Configuration
committed by user 'system'. Use 'show configuration commit changes 1000000021' to view the changes.

The system log confirms that the IP address change has been committed to the IOS XR configuration automatically.

Verify that the new IP address is configured on the interface.

Example:

[ios:~]$ifconfig Hu0_0_0_24
Hu0_0_0_24  Link encap:Ethernet  HWaddr 78:e7:e8:d3:20:c0
            inet addr:10.1.1.10  Bcast:0.0.0.0  Mask:255.255.255.0
            BROADCAST MULTICAST  MTU:1500  Metric:1

The IP address 10.1.1.10 appears on the interface, confirming that the configuration was applied successfully.

The new IP address is configured on the Linux-managed interface and the change is automatically committed to the IOS XR configuration.

Configure custom MTU setting

Use this procedure to set a custom maximum transmission unit (MTU) on a Linux-managed interface and confirm that the updated MTU is reflected in both the Linux interface configuration and the IOS XR running configuration.

Procedure

Configure the MTU setting.

Example:

[ios:~]$ifconfig Hu0_0_0_24 up

[ios:~]$Router:Aug 1 17:41:54.824 UTC: ifmgr[266]: %PKT_INFRA-LINK-3-UPDOWN : Interface
HundredGigE0/0/0/24, changed state to Down
Router:Aug 1 17:41:54.824 UTC: ifmgr[266]: %PKT_INFRA-LINEPROTO-5-UPDOWN : Line protocol on
Interface HundredGigE0/0/0/24, changed state to Down
Router:Aug 1 17:41:56.448 UTC: xlncd[253]: %MGBL-CONFIG-6-DB_COMMIT : Configuration committed by
user 'system'. Use 'show configuration commit changes 1000000022' to view the changes.
Router:Aug 1 17:41:56.471 UTC: ifmgr[266]: %PKT_INFRA-LINK-3-UPDOWN : Interface
HundredGigE0/0/0/24, changed state to Up
Router:Aug 1 17:41:56.484 UTC: ifmgr[266]: %PKT_INFRA-LINEPROTO-5-UPDOWN : Line protocol on
Interface HundredGigE0/0/0/24, changed state to Up
Router:Aug 1 17:41:58.493 UTC: xlncd[253]: %MGBL-CONFIG-6-DB_COMMIT : Configuration committed by
user 'system'. Use 'show configuration commit changes 1000000023' to view the changes.

[ios:~]$
[ios:~]$ip link set dev Hu0_0_0_24 mtu 4096
[ios:~]$
[ios:~]$Router:Aug 1 17:42:46.830 UTC: xlncd[253]: %MGBL-CONFIG-6-DB_COMMIT : Configuration
committed by user 'system'. Use 'show configuration commit changes 1000000024' to view the changes.

Verify that the MTU setting has been updated in Linux.

Example:

[ios:~]$ifconfig
Hu0_0_0_24 Link encap:Ethernet HWaddr 78:e7:e8:d3:20:c0
inet addr:10.1.1.10 Bcast:0.0.0.0 Mask:255.255.255.0
inet6 addr: fe80::7ae7:e8ff:fed3:20c0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:4096 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:648 (648.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
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
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

Check the effect on the IOS XR configuration with the change in MTU setting on this interface.

Example:

Router#show running-config int HundredGigE0/0/0/24
interface HundredGigE0/0/0/24
 mtu 4110
  vrf blue
  ipv4 mtu 4096
  ipv4 address 10.1.1.10 255.255.255.0
  ipv6 mtu 4096
  ipv6 address fe80::7ae7:e8ff:fed3:20c0 link-local
  !
 !
!
Router#
Router#show ip int br | i HundredGigE0/0/0/24
HundredGigE0/0/0/24 10.1.1.10 Up Up blue

The output indicates that the interface acts as a regular Linux interface, and IOS XR configuration receives inputs from Linux.

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