Cisco IOS XR

According to Cisco's product literature, IOS XR shares very little infrastructure with the other IOS trains, and is instead built upon a "preemptive, memory protected, multitasking, microkernel-based operating system".^[1] The microkernel was formerly provided by QNX;^[2] versions 6.0 up to 7.5.2 use the Wind River Linux distribution.^[3]. From version 7.6.1 and onwards, the kernel has been switched to OpenEmbedded.

IOS XR aims to provide the following advantages over the earlier IOS trains:

• Improved high availability (largely through support for hardware redundancy and fault containment methods such as protected memory spaces for individual processes and process restartability)
• Better scalability for large hardware configurations (through a distributed software infrastructure and a two-stage forwarding architecture)
• Apackage based software distribution model (allowing optional features such as multicast routing and MPLS to be installed and removed while the router is in service)
• The ability to install package upgrades and patches (potentially while the router remains in service)
• A web-based GUI for system management (making use of a generic, XML management interface)

IOS XR was announced along with the CRS-1 in May 2004.^[4] The first generally available version was 2.0.

Some significant releases include the following.

• 3.2 – first generally available version for the 12000 router series
• 3.9 – first generally available version for the ASR 9000 router series
• 5.0 – first generally available version for the NCS6000 series, which is based upon a Linux kernel instead of QNX, and was released in September 2013^[5]
• 6.1.1 - Introduces support for the 64-bit Linux-based IOS XR operating system on ASR 9000 series ^[6]

An example BGP configuration for IOS and IOS XR is shown.

More examples can be found in the Cisco document Converting Cisco IOS Configurations to Cisco IOS XR Configurations.^[7]

IOS

router bgp 109
  no synchronization
  bgp log-neighbor-changes
  neighbor 203.0.113.1 remote-as 109
  neighbor 203.0.113.1 update-source Loopback0
  no auto-summary

IOS XR

router bgp 109
  neighbor 203.0.113.1
    remote-as 109
    update-source Loopback0

• Cisco IOS
• Cisco IOS XE
• Cisco NX-OS

• Cisco Content Hub
• Cisco Feature Navigator
• Cisco IOS XR Support Page
• Cisco Aggregation Services Router 9000 Series Support Page
• Cisco Carrier Routing System Support Page
• Cisco multimedia documentation - covering IOS XR and its supported systems
• Cisco Security Advisories
• HEAnet's New Network and Working with IOS-XR