BFD-triggered Fast Reroute (FRR) in IOS XR

Answered Question
Aug 19th, 2010
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I'm migrating the configuration from a Cisco 12416 router running Cisco IOS, to a CRS1 router running IOS-XR.

In IOS I have configured the following command for FRR "ip rsvp signalling hello bfd". I cannot find the way to configure this parameter using IOS-XR.

I don't know if anyone can help me with this request.

Thanks.

Jose.

Correct Answer by Atif Awan about 6 years 11 months ago

In IOS-XR BFD triggered FRR is enabled under the mpls traffic-eng configuration mode. A sample is:



mpls traffic-eng

interface POS0/0/0/0

  backup-path tunnel-te XXXX

  bfd fast-detect

!

bfd minimum-interval 150

bfd multiplier 3

!


I will suggest you read the IOS-XR BFD configuration guide just to get up to speed with the details:


http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.6/interfaces/configuration/guide/hc36bifw.html (Release 3.6 ... You can find this for subsequent releases on Cisco's website as well using the master link http://www.cisco.com/en/US/products/ps5845/products_installation_and_configuration_guides_list.html)



Atif

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Correct Answer
Atif Awan Thu, 08/19/2010 - 22:32
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  • Cisco Employee,

In IOS-XR BFD triggered FRR is enabled under the mpls traffic-eng configuration mode. A sample is:



mpls traffic-eng

interface POS0/0/0/0

  backup-path tunnel-te XXXX

  bfd fast-detect

!

bfd minimum-interval 150

bfd multiplier 3

!


I will suggest you read the IOS-XR BFD configuration guide just to get up to speed with the details:


http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.6/interfaces/configuration/guide/hc36bifw.html (Release 3.6 ... You can find this for subsequent releases on Cisco's website as well using the master link http://www.cisco.com/en/US/products/ps5845/products_installation_and_configuration_guides_list.html)



Atif

jbaraona Fri, 08/20/2010 - 08:26
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Thanks a lot for your help Atif.

I will test the configuration in my lab environment and post the results.


Thanks again for your help.


Jose

smailmilak Wed, 09/21/2011 - 12:52
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Hi,


and results?

How was the test and have you got sub-second failover?


I am trying to achieve fast convergence with IP fast reroute (IP FRR) without MPLS TE.

The problem is that I don't know how to test it. With ICMP I don't get any packets lost when I shut down the interface

that is forwarding the traffic. But I don't know how to find out the time for reconvergence.

I am using BFD, too, but looks like that I get the same failover time without BFD.


The OSPF timers are these on CRS8 IOS-XR 4.0.3:

timers throttle lsa all 0 20 5000

timers throttle spf 24 24 5000

timers lsa min-arrival 20

jbaraona Thu, 09/22/2011 - 23:25
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Hello,

I you want convergence times of 10-20ms you need MPLS TE.

we also change OSPF timers to have fast IGP convergence, this is the configuration we use based on Cisco recommendations:


!

router ospf

ispf

nsf ietf

mpls ldp sync

timers throttle lsa all 0 20 5000

timers throttle spf 50 50 5000

timers lsa arrival 15

timers pacing flood 15

!

mpls ldp igp sync holddown 60000

!


hope this helps.

smailmilak Thu, 09/22/2011 - 23:37
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Thank you for the config.


We have similar timers, but I deleted timers pacing flood because I read that it is not recommended to change it.


Do you lose a packet after a failover? When I do an ICMP test and after I administravly shut down the forwarding interface no packets get lost, but when I simulate a link down so that I shut down the interface on the other side I lose one packet.

Maybe my understanding of sub-second convergence is wrong, maybe it is ok that a packet gets lost!


OSPF needs only 28msec to steer the traffic over the backup path but I can not measure the link down time detection. 

jbaraona Fri, 09/23/2011 - 00:19
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Hello,

You have to combine other things like:


ip routing protocol purge interface (global configuration)


interface GigabitEthernet x/y

carrier-delay up msec 500

carrier-delay down msec 0


let me know how that works.

smailmilak Fri, 09/23/2011 - 01:02
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Hi,


still one packet loss. I typed carrier-delay on both routers IOS and IOS-XR but "ip routing protocol purge interface" only on IOS because I could not find it on IOS-XR.


I have to say that the router are connected via DWDM and distance is maybe 30km, not sure if this is that important?

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