Date: Mon, 02 Apr 2018 14:33:44 +0200 From: Harry Schmalzbauer <freebsd@omnilan.de> To: Daniel Braniss <danny@cs.huji.ac.il> Cc: freebsd-virtualization@freebsd.org Subject: Re: bhyve and arp problem Message-ID: <5AC22328.8060306@omnilan.de> In-Reply-To: <DEA10FBE-E8F8-46C3-816C-DB61421BF0A5@cs.huji.ac.il> References: <DEA10FBE-E8F8-46C3-816C-DB61421BF0A5@cs.huji.ac.il>
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Bezüglich Daniel Braniss's Nachricht vom 30.03.2018 13:16 (localtime): > hi, > this is my first attempt at bhyve, and so far all seems ok, except > in my guest, the mac address of the hosting keeps flipping, ie, every 20 minutes > i see a message : > … arp: nnn (the hosting ip) moved from xxxx to yyyy > on both the host and guest I’m running a very resent -stable. > the yyyy is the mac of the host nic, while the xxxx is the tap0 > > i know this looks harmless, but it’s annoying You can calm it with 'sysctl net.link.ether.inet.log_arp_movements=0' There's also "net.link.ether.inet.log_arp_wrong_iface" and "net.inet.ip.check_interface" which influence related behaviour. You also posted (documentationized IP-addresses): > I think the problem starts with the host seeing the client/guest on 2 interfaces, the nic (mlnxen0) and the tap(tap0) > on the host: > > arp -a > ... > bhv-00.cs.huji.ac.il (192.0.2.246) at xx.xx.xx.xx.xx on tap0 expires in 1001 seconds [ethernet] > bhv-00.cs.huji.ac.il (192.0.2.246) at xx.xx.xx.xx.xx on mlxen0 expires in 644 seconds [ethernet] Initially, you reference two MAC-addresses with xxxx and yyyy. The recent post indicates non-different MAC-addresses. If xxxx and yyyy - resp. xx.xx.xx.xx.xx - are equal (but seen on different interfaces), this wouldn't get logged I think. But it was the only harmless case for straight forward setups. Even with STP/LACP/CARP/etc. in place, "arp: IP-address moved" always indicates a misconfiguration and I don't know any example where the two different MAC-Addresses for one IP-address were harmless. While using a single (locally administrated?) MAC address more than once sitewide _can_ make sense, having two interfaces on one host which both are on the same ethernet segment like the two interfaces with the same MAC address, looks like an unintended setup. So I strongly suggest to analyze your setup before altering the mentioned sysctl!!! -harry
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