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Ask the Expert: Introduction to Cisco IOS XR Software

Community Manager
Community Manager

Welcome to this Cisco Support Community Ask the Expert conversation. This is an opportunity to learn and ask questions about basic fundamental difference between Cisco IOS Software and Cisco IOS-XR Software with Cisco subject matter expert Anilkumar Dantu.

Anil will explain how Cisco IOS-XR Software as an operating system is packaged, the boot-up procedure in Cisco IOS-XR Software, basic configuration, and configuration file system difference between Cisco IOS Software and Cisco IOS-XR Software. Additionally, Anil will cover troubleshooting approaches on Cisco IOS-XR Software nodes.

For more information to go IOS XR Introduction.

Anilkumar Dantu is a customer support engineer in High-Touch Technical Services at Cisco specializing in service provider technologies and platforms. He serves as a support engineer for technical issues supporting Cisco IOS XR Software customers on Cisco CRS and Cisco XR 12000 Series Routers. Anil has more than 10 years of experience in the IT industry and holds CCIE certification (22536) in routing and switching.

Remember to use the rating system to let Anil know if you have received an adequate response. 

Because of the volume expected during this event, Anil might not be able to answer every question. Remember that you can continue the conversation in the Service Providers community, under subcommunity XR OS and Platforms, shortly after the event. This event lasts through July 3, 2014. Visit this forum often to view responses to your questions and the questions of other Cisco Support community members.

1 Accepted Solution

Accepted Solutions

Hi Ashvin,

                 Thanks for your kind comments. Please see my answers inline.


==> When you were changing the OS from IOS to IOS XR.. at that time you have shown the boot image with  sh dir command and the IOS XR was place in the disk 0:

My question is .. from where did you get this IOS XR placed in disk o:?   Was it already there in router? or did you save in router from TFTP server?


Anil:  Prior to IOS to XR conversion. My GSR lab router was booted from bootflash: and I had copied the .vm files to disk0: using TFTP.


Normally prior to planning IOS to XR conversion , you need to make sure that your mini.vm file is available on one of the disks (disk0: or disk1; or compact flash) or you can also load them from TFTP server (proper TFTP setting needed in romon for this).


TURBOBOOT=on,disk0          - This command in romon, says that during turboboot process extracted packages from mini.vm file will be stored in disk0 location. Even your future PIE files , SMU files you wish to install will also be extracted and copied to disk0: location. So disk0: in above TURBOBOOT command mentions your destination location where extracted packages of mini.vm file, extracted PIE files & extracted SMU files will get installed.


++while second command (boot disk0:c12kmini.vm) is used to point towards source location where your unextracted mini.vm files, PIE files & SMU files  are present. In my video I have  loaded un-extracted c12kmini.vm file in disk0: (as I had only single disk0: as it was a test lab router). But in case you have have mutliple disks (which is normally the case with production routers) you will be keeping your source files (c12kmini.vm , PIEs & SMU) in one disk or use TFTP and loading the extracted files to other disk (disk0: or disk1; or compact flash).


In summary:

TURBOBOOT=on,disk0         -- disk0: points to destination where extracted files after turboboot will be copied.


boot disk0: or boot disk1: or boot compactflash: or boot tftp:    -----This command points to location where your source files (c12kmini.vm , PIEs & SMU) are stored.





=== > What is SDR and what is it's importance in IOS XR?

Anil : SDR is secure domain router. In XR we have capability of logically dividing a physical router into logical routers. Each of these logical routers will be acting as individual routers & will be having separate configs. You can carve out SDRs from Admin mode by grouping RPs & LC into individual SDRs. Incase no SDRs are configured then router acts as a single SDR router. Please note RPs & LC only belongs to individual SDRs while your fabric cards, power supply, alarms cards etc will be part of admin resources & remain common to all SDRs.




=== > If we buy a brand new GSR router then what would be the default IOS in flash? Will it be IOS or IOS XR as it supports IOS & IOS XR both.. 


Do we need to check in flash file whether which one is set as boot file in flash? 


Anil:  Default OS in flash will depend on what OS (IOS or XR) is purchased from Cisco.  Please note that  XR package when unpacked will have hugh size (approx 1 to 1.5 GB),  hence will be normally loaded in disk0 or disk1 or compactflash which are normally in 4GB range in PRP-2 or PRP-3 processor cards in GSR.


Yes.. in case you are converting a node from IOS to XR, then in romon, you need to first unset the boot variable prior to start of TURBOBOOT process.. Then TURBOBOOT process will automatically set the boot variable to load XR from disk as part of the process itself.


=== > Can we keep both IOS & IOS XR in the same disk ( for exp disc 0:) if it has sufficient space available?

Anil:  Yes... you can. As part of TURBOBOOT process boot variable will getting changed to load XR. This is not an issue. But normally we will be using a dedicated disk. As all OS & config files will be stored in disk in case of node running XR while in IOS- all OS & config files are in memory while node is running.







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13 Replies 13

Hello Anil,

How do I identify in XR whether a process is a kernel process or non-kernel process?  And whether it is a critical process for node to be up and running; so that  care can be taken while manually restarting a process? Appreciate your help on this.


Thank you,


Hi Lisa,

            Greetings. In IOS XR- Microkernel & the process manager together form PROCNTO process. Procnto process is a main kernel process in XR.  Apart from these there are few kernel services which assist in kernel operations are part of Kernel processes. As discussed in the trai