why doesn't broadcast ping work?

Question

I have Freebsd as a router.
Local network is on interface sk0: inet 10.254.239.1 netmask 0xffffff00 broadcast 10.254.239.255
In my local network I have a computer(windows 7) that gets it's ip(10.254.239.2) from DHCP server on Freebsd.

• Ping to exact address 10.254.239.2 works fine.

When I try to ping bradcast 10.254.239.255 from Freebsd itself nothing happens:

--- 10.254.239.255 ping statistics ---
3 packets transmitted, 0 packets received, 100.0% packet loss

• #arp -a says:
  ...
  ? (10.254.239.255) at (incomplete) on sk0 expired [ethernet]
  ...

• Firewall allows all on this interface

Where to look? What to do to make broadcast working?

Answer 1

Most operating systems simply ignore broadcast ICMP pings by default, for security reasons. You don't "make it work", and it has no effect on other kinds of broadcasts.

---

On FreeBSD, the net.inet.icmp.bmcastecho sysctl toggles this feature.