Need clarication on BFD template on single hop

[kossuth78]

Cisco's documentation on a single hop implementation isn't all that great and most everything I've run into covers just multihop configurations.  Need some help on understanding setting up a single hop template with dampening.  In short we are interconnecting into a 3rd party vendor and having some BFD issues.  The Cisco platform is a ISR4k.  BFD comes up and then flaps.  Hoping we can tailor dampening to bring the flapping issue under control.  Does anybody have any documentation to share?

[MHM Cisco World]

are you sure the 3rd party can run BFD?

[kossuth78]

100% certain it does.  This deployment is large and there are routers which are close which have no problems establishing bfd sessions. There are many (not all though) that have issue thus looking how to fix/correct it. 

[MHM Cisco World]

IP Routing Configuration Guide, Cisco IOS XE 17.x - BFD Dampening [Cisco ASR 1000 Series Aggregation Services Routers] - Cisco

single hop is direct connect mutlihop is there is one or more hop between the BFD router  
for damping check the link above (note I think you can apply same config under the ISR4K both use IOS XE)

[paul driver]

Hello
You dont mention what routing protocol you are using and what BFD configuration template you’ve applied for multihop peering reachable over multiple physical links.

in anycase if you peering/adjacency flaps after you have implemented BFD then it seems to suggest BFD is declaring the session dead, due to not receiving its echo packets within it specified rate limit so have you checked your routing paths for any latency

[kossuth78]

Routing is ospf for what matters.  This isn’t multi hop, it’s single hop given there is a /30 tunnel connection between the two endpoints.  As I said I haven’t found any documentation on single-hop that answers my above question. Connections are solid.  A static route without BFD works absolutely fine with no packet loss. Unfortunately for production we MUST use BFD with OSPF due to other requirements in the environment. 

[paul driver]

Hello

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@kossuth78 wrote:

A static route without BFD works absolutely fine with no packet loss. Unfortunately for production we MUST use BFD with OSPF due to other requirements in the environment. 

 BFD comes up and then flaps.  Hoping we can tailor dampening to bring the flapping issue under control. 

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Is BFD enable OSPF globally or interface specific?
I assume the BFD is set the same at both ends of the tunnel ( interval, min_rx) and you haven't turned echo off?

can you share output.
debug bfd events
sh bfd neighbours detail?

[MHM Cisco World]

IOU1#show run
!
bfd map ipv4 3.3.3.3/32 1.1.1.1/32 mhm
bfd-template multi-hop mhm
interval min-tx 50 min-rx 50 multiplier 3
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface Loopback10
ip address 11.11.11.11 255.255.255.255
!
interface Ethernet0/0
ip address 100.0.0.1 255.255.255.0
!
router bgp 100
bgp log-neighbor-changes
network 11.11.11.11 mask 255.255.255.255
neighbor 3.3.3.3 remote-as 300
neighbor 3.3.3.3 ebgp-multihop 255
neighbor 3.3.3.3 update-source Loopback0
neighbor 3.3.3.3 fall-over bfd multi-hop
!
ip route 0.0.0.0 0.0.0.0 100.0.0.2
ip route 3.3.3.3 255.255.255.255 100.0.0.2

IOU3#show run
!
bfd map ipv4 1.1.1.1/32 3.3.3.3/32 mhm
bfd-template multi-hop mhm
interval min-tx 50 min-rx 50 multiplier 3
!
interface Loopback0
ip address 3.3.3.3 255.255.255.255
!
interface Ethernet0/0
no ip address
shutdown
!
interface Ethernet0/1
no ip address
shutdown
!
interface Ethernet0/2
no ip address
shutdown
!
interface Ethernet0/3
no ip address
shutdown
!
interface Ethernet1/0
no ip address
shutdown
!
interface Ethernet1/1
ip address 200.0.0.3 255.255.255.0

!
router bgp 300
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 ebgp-multihop 255
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 fall-over bfd multi-hop

this simple example of using multi hop 
IOU1 and IOU2 run bgp there are not direct connect there is one hop inbetween 
so we need multi-hop 
bfd map & bfd-template multi-hop to make BGP use BFD to detect neighbor failed 


for single hope, in simple word you have 10 interface  for direct connect neighbor (single hop) and you need to config same interval/max/min/echo.. for all, it better to config one bfd-template and then only under each interface named ther bfd-template you want
that it.