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Hi
The only situation where I can imagine this happening is a PVE host that has
Proxy ARP enabled.
This is not enabled by default AFAIK.
root@pve5:~# sysctl net.ipv4.conf.all.proxy_arp
net.ipv4.conf.all.proxy_arp = 0
On my PVE7 hosts, all the kernel’s ARP features are in fact off (by default).
root@pve5:~# sysctl -a | fgrep arp | grep -vc ' = 0$'
0
> Somehow, the other physical servers connected to ens19 get an ARP reply with
> the mac address of ens19 for the IP on vmbr1 (which, again, has no physical
> interface).
Even if Proxy ARP were configured on your PVE7 hosts, your servers would
normally only get an ARP reply when they send a specific ARP request e.g. “who
has 10.A.B.C, tell 10.A.B.D”.
Here are questions you should ask yourself:
Why would your servers configured with IP 10.X.Y.Z and connected to vmbr2 via
ens19 send ARP requests for 10.A.B.C/24 on that link?
Why do they? How do the requests look like (who is asking)?
Hope that helps in tracking it down.
Stefan
> On Nov 23, 2021, at 20:58, ic <[email protected]> wrote:
>
> Hi,
>
> I’m running PVE 7.0 on a bunch of servers. I noticed something strange.
> There is a vmbr2 containing one physical interface (ens19) with an IP
> (10.X.Y.Z/24).
> There is a vmbr1 containing NO physical interface with another IP
> (10.A.B.C/24) (outside of the range of vmbr2, even if this is irrelevant for
> this problem).
>
> Somehow, the other physical servers connected to ens19 get an ARP reply with
> the mac address of ens19 for the IP on vmbr1 (which, again, has no physical
> interface).
>
> In an “ip a” output, this mac address appears only in ens19 and vmbr2. vmbr1
> has its own mac (different from the physical mac of ens19/vmbr2).
>
> What am I missing?
>
> In my setup I need vmbr2 to have the same IP on each physical host and not
> leak on the outside network so this is pretty annoying :(
>
> BR, ic
>
>
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