BFD with OSPF on Cisco ASR9K Series

[zizou6500]

Hi Community,

I need your help to enable BFD with OSPF in ASR 9000 series using the optimal configuration.

Currently using only OSPF isn't enough to have a fast convergence, could you please help me with this?

Thanks in advance.

[MHM Cisco World]

https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k-r7-5/routing/configuration/guide/b-routing-cg-asr9000-75x/implementing-BFD.html#ID1121

check this guide

[pman]

Hi,

The following example shows how to enable BFD for OSPF on a Gigabit Ethernet interface:

RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# router ospf 0
RP/0/RSP0/CPU0:router(config-ospf)# area 0
RP/0/RSP0/CPU0:router(config-ospf-ar)# interface gigabitEthernet 0/3/0/1
RP/0/RSP0/CPU0:router(config-ospf-ar-if)# bfd fast-detect
RP/0/RSP0/CPU0:router(config-ospf-ar-if)# commit
RP/0/RSP0/CPU0:Dec 2 07:06:48.508 : config[65685]: %MGBL-LIBTARCFG-6-COMMIT :
Configuration committed by user 'xxx'. Use 'show configuration commit changes 1000001134'
to view the changes.
RP/0/RSP0/CPU0:router(config-ospf-ar-if)# end
RP/0/RSP0/CPU0:Dec 2 07:06:48.848 : config[65685]: %MGBL-SYS-5-CONFIG_I : Configured from
console by lab
RP/0/RSP0/CPU0:router# show run router ospf
router ospf 0
area 0
interface GigabitEthernet0/3/0/1
bfd fast-detect

The following example shows how to enable BFD for OSPFv3 on a Gigabit Ethernet interface:

RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# router ospfv3 0
RP/0/RSP0/CPU0:router(config-ospfv3)# bfd minimum-interval 6500
RP/0/RSP0/CPU0:router(config-ospfv3)# bfd multiplier 7
RP/0/RSP0/CPU0:router(config-ospfv3-ar)# area 0
RP/0/RSP0/CPU0:router(config-ospfv3-ar)# interface gigabitethernet 0/1/5/0
RP/0/RSP0/CPU0:router(config-ospfv3-ar-if)# bfd fast-detect
RP/0/RSP0/CPU0:router(config-ospfv3-ar-if)# commit
RP/0/RSP0/CPU0:router(config-ospfv3-ar-if)# end
RP/0/RSP0/CPU0:router# show run router ospfv3
router ospfv3
area 0
interface GigabitEthernet0/1/5/0
bfd fast-detect

https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k_r4-2/interfaces/configuration/guide/hc42bifw.html#wp1021342

[zizou6500]

@pman By default the BFD timers values are 450ms(150ms*3), could you please tell me what is the minimum value I could set?

[pman]

Hi,

by cisco 15 is the minimum:

Step 3

bfd minimum-interval milliseconds Example: RP/0/RSP0/CPU0:router(config-ospf)# bfd minimum-interval 6500

Sets the BFD minimum interval. Range is 15-30000 milliseconds. This example sets the BFD minimum interval to 6500 milliseconds.

https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k_r4-2/interfaces/configuration/guide/hc42bifw.html#wp1013098

from my equipment I see the following output:

RP/0/RP0/CPU0:ios(config-ospf)#bfd minimum-interval ?
<50-30000> hello interval in milli-seconds

!

RP/0/RP0/CPU0:ios(config-ospf)#bfd multiplier ?
<3-50> Detect multiplier

[MHM Cisco World]

Sets the BFD minimum interval. Range is 15-30000 milliseconds.

from guide I mention before 
min from 15-30000 mSec.

I think this enough for OSPF 

[paul driver]

Hello

How fast do you want convergence, ospf does have fast detection of its own for loss of neighboring peers without BFD?

int x/x/
ip ospf dead-interval minimal hello-multiplier x

[zizou6500]

Hi @paul driver ,

Yes I know, OSPF fast detection is already enabled but this is not fast enough that's why I'm looking at the BFD config.

[Joseph W. Doherty]

How "fast" lost of OSPF neighbor detection do you wish to achieve?

BTW, cannot say for 9K ASRs, but on lessor Cisco platforms, we didn't find BFD all that much faster that Cisco's fast-hellos.  The huge plus, though, for using BFD, it's much less resource intensive especially if you have lots of instances using it.

Also, since you mention fast OSPF convergence, you do realize there much more to it than just OSPF dropped neighbor detection?  If not, Cisco has (or at least had) a nice white paper explaining their proprietary settings to change to achieve fast(er) OSFP convergence.

I also recall, Cisco's EIGRP can achieve (with tweaking) even faster convergence than OSFP.  (I think that because EIGRP can have a feasible successor route while OSPF has to recalc a change in topology [Cisco's OSPF iSPF feature can help there, sometimes].)