[c-nsp] Link down affecting BGP peer

[Hank Nussbacher]

On 18/05/2022 17:36, Blake Dunlap wrote:

Others have explained this.  Basically, a BGP peer gets locked onto one 
of the LAG links and will migrate to another link in the event that the 
specific link goes down.  This is normal behavior.

-Hank

> Is it about 4000 msec of flapping? Perhaps the bundle member in question 
> is delaying to go down for some reason?
> 
> On Thu, May 5, 2022, 11:07 Hank Nussbacher <hank at interall.co.il 
> <mailto:hank at interall.co.il>> wrote:
> 
>     I have 4 individual links defined as part of a Bundle-ether (IOS-XR
>     5.3.3 on ASR9010):
> 
>     interface TenGigE0/2/0/1
>        bundle id 2 mode active
>        flow-control bidirectional
>        carrier-delay up 100 down 4000
>     ! They are all part of a bundle...
>     interface Bundle-Ether2
>        mtu 9192
>        bundle minimum-active links 2
> 
>     When I shut off just 1 of these 4 links - the bundle stays up yet
>     certain BGP sessions flap for about 5 seconds - different peers
>     depending on which of the 4 links gets turned down.
> 
>     My BGP config:
>     router bgp 378
>        rpki server x.139.197.151
>         transport tcp port 8282
>         refresh-time 600
>        !
>        bgp log neighbor changes detail
>        address-family ipv4 unicast
>         bgp dampening 5 750 3000 10
>         bgp attribute-download
>     !
>        neighbor x.x.125.1
>         remote-as xxxx5
>         address-family ipv4 unicast
>          send-community-ebgp
>          soft-reconfiguration inbound
> 
>     What could be causing the bgp peer to flap even though the LAG stays up?
> 
>     Thanks,
>     Hank
> 
> 
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