CentOS to Debian migration issue

[Pavlo Astakhov]

Hello, all

I got a weird question. We recently migrated two our routers from CentOS 
7 to Debian 10, installed Bird, placed config files back - and since 
then we are observing BGP flaps.

Moreover, flaps are observed on IPv6 peers only:

Name       Proto      Table      State Since         Info
device1    Device     ---        up     2021-03-18 15:42:27
direct1    Direct     ---        up     2021-03-18 15:42:27
kernel1    Kernel     master4    up     2021-03-18 15:42:27
kernel2    Kernel     master6    up     2021-03-18 15:42:27
static1    Static     master4    up     2021-03-18 15:42:27
static2    Static     master6    up     2021-03-18 15:42:27
UPLINK     BGP        ---        up     2021-03-18 15:42:31 Established
UPLINKv6   BGP        ---        up     2021-03-22 21:11:12 Established
AR1        BGP        ---        up     2021-03-18 15:42:31 Established
AR1v6      BGP        ---        up     2021-03-19 23:42:55 Established
AR2        BGP        ---        up     2021-03-18 15:42:28 Established
AR2v6      BGP        ---        up     2021-03-20 15:37:38 Established
BR2        BGP        ---        up     2021-03-18 15:42:28 Established
BR2v6      BGP        ---        up     2021-03-21 11:03:33 Established
ospf4      OSPF       master4    up     2021-03-18 15:42:27 Running
ospf6      OSPF       master6    up     2021-03-18 15:42:27 Running

Flaps are unregular, currently we saw no coincedences with anything. The 
network is stable, our and peers configs were not changed, Bird version 
too (2.0.7 on both CentOS and Debian).

The only message about this in logs is hold-related:

2021-03-22 21:01:10 <WARN> Kernel dropped some netlink messages, will 
resync on next scan.
2021-03-22 21:04:33 <WARN> Kernel dropped some netlink messages, will 
resync on next scan.
2021-03-22 21:06:10 <WARN> Kernel dropped some netlink messages, will 
resync on next scan.
2021-03-22 21:10:12 <RMT> UPLINKv6: Error: Hold timer expired
2021-03-22 21:10:13 <WARN> Kernel dropped some netlink messages, will 
resync on next scan.
2021-03-22 21:10:15 <WARN> Kernel dropped some netlink messages, will 
resync on next scan.
2021-03-22 21:10:16 <WARN> Kernel dropped some netlink messages, will 
resync on next scan.
2021-03-22 21:10:16 <WARN> Kernel dropped some netlink messages, will 
resync on next scan.

Could you please suggest some way to go except of returning to CentOS?

Thank you in advance.

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