CentOS to Debian migration issue

[Honghao Zeng]

We had a similar issue when we migrated to debain a while back; flapping sessions, weird timeouts, etc. Tweaking `net.ipv6.route.max_size' helped. Some clues:

- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=861115#10
- https://bird.network.cz/pipermail/bird-users/2020-February/014270.html

Regards,
Honghao Zeng

> On Mar 22, 2021, at 4:29 PM, Pavlo Astakhov <jared at jared.kiev.ua> wrote:
> 
> 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.
> 
> --