Re: Duplicates IP packets when using CARP and ECMP routes.

Reply: Arnaud Houdelette-Langlois : "Re: Duplicates IP packets when using CARP and ECMP routes."
In reply to: Arnaud Houdelette-Langlois : "Duplicates IP packets when using CARP and ECMP routes."
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From: Alexander Chernikov <melifaro_at_FreeBSD.org>
Date: Sat, 29 Apr 2023 21:44:02 UTC


On Sat, 29 Apr 2023, at 11:01 AM, Arnaud Houdelette-Langlois wrote:
> Hi.
> 
> We got a freebsd router with both ospf/bpg and multipath routes (ECMP) (using the new bird2 with netlink) .
> 
> The router got an interface with carp enabled on it (gateway for admin vlan).
> 
> Packets received on the carp address gets routed on all known routes towards destination. Thus, the destination host receives duplicates ip packets. (which disrupts most udp based protocols)
> 
> Using a simple alias instead of carp solve the problem. Is this a known problem, or should I fill a PR ?
> 
No, that’s not a known problem. 
Please do open the PR with details.
> -- 
> Arnaud Houdelette-Langlois
> Administrateur des infrastructures systèmes et réseaux
> Normandie Université
> +33 2 31 56 69 54
> 

/Alexander