bhyve and arp problem

[Rodney W. Grimes]

> > On 2 Apr 2018, at 15:33, Harry Schmalzbauer <freebsd at omnilan.de> wrote:
> > 
> > Bez?glich 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]
> > 
> 
> the above 2 lines are on the host running bhyve (server?) and the MACs belong to the client, and they are identical,
> there is no complaints.
> (BTW, did you change the ip?s?)
> 
> > Initially, you reference two MAC-addresses with xxxx and yyyy.
> this is on the client, where the MAC are different (it?s of the hosting computer).
> 
> > 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!!!
> > 
> I do want to know if there are ip/mac issues, it usually happens when more than one host has the same ip,
> which is not the case here :-(

Are you trying to use the HOSTS ip address in the GUEST?
And how do you have an mlxen interface in a GUEST?
Is this being done with PCI passthrough?


-- 
Rod Grimes                                                 rgrimes at freebsd.org