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Re: Static interface routes for IP address on different subnet doesn't send an ARP who-has

Christos Zoulas wrote:
In article <>, Peter Kieser  
<> wrote:


I have an ISP that requires that I use a subnet mask of (/32) which requires that I add a static interface route for the gateway IP address because it's on a different subnet ( In Linux and FreeBSD this works as intended, and the network stack sends an ARP request for the gateway IP address when a static route is added.

On NetBSD, the network stack seems to make up a random MAC address and I don't see an ARP who-has request sent. Below, you can see that the MAC address of the gateway ( is correct when the subnet is set to /27:

watson# arp -a
? ( at 52:54:00:07:a6:f6 on vioif0
watson# ifconfig vioif0
    address: 52:54:00:24:c2:c3
    inet netmask 0xffffffe0 broadcast
    inet6 fe80::5054:ff:fe24:c2c3%vioif0 prefixlen 64 scopeid 0x1

If I set the subnet and broadcast domain how my ISP wants it, and follow the MAC address is replaced with garbage data:

watson# ifconfig vioif0 inet netmask broadcast
watson# route add -host -link -iface vioif0
add host gateway vioif0
watson# ping
PING ( 48 data bytes
---- PING Statistics----
3 packets transmitted, 0 packets received, 100.0% packet loss
watson# arp -a
? ( at 76:69:6f:69:66:30:00:0e:00:00:00:00 on vioif0 permanent

Now, if I add the MAC address of the gateway (which isn't a reasonable solution, since my ISP has HRSP and other failovers setup) everything works out:

watson# route add -host -link -iface vioif0:52540007a6f6

Does anyone have any idea how to get this configuration to work without the MAC address of the gateway being specified for the route? I feel like this is a bug, as with Linux and FreeBSD this configuration (while I believe it's not particular sane) works just fine, the operating system does an ARP who-has request and you can access the default gateway.

Looks like a bug :-) What is the correct MAC for the gateway?

Christos is right. The problem with a netmask of reminds me
of getting a 3G/4G USB modem to work because that was how the telco was
answering the conversation.

And looking at how you went about getting it to work does not seem right.

In this case the vioif is not a broadcast link (subnet mask is so quite clearly nothing else can be on that subnet), it is a point to point link.

Did you try doing this:

# ifconfig vioif0 inet



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