Cisco IOS XR


IOS XR is a release train of Cisco Systems' widely deployed Internetwork Operating System (IOS), used on their high-end Network Convergence System and carrier-grade routers such as the ASR 9000 series and Carrier Routing System series of routers.

Architecture

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". The microkernel was formerly provided by QNX; versions 6.0 up to 7.5.2 use the Wind River Linux distribution. 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:
IOS XR was announced along with the CRS-1 in May 2004. 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
  • 6.1.1 - Introduces support for the 64-bit Linux-based IOS XR operating system on ASR 9000 series

    Differences between IOS and IOS XR

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.
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