Re: Should ipaliased IP addresses answer broadcast packets?

From: Pekka Savola (
Date: Sun Jan 20 2002 - 08:30:49 EST

On Sun, 20 Jan 2002, Rob Fulton wrote:
> The game client has however been unable to connect to the server, using
> tcpdump I can see the request from the server going to the broadcast address
> as shown below.
> 11:53:01.315928 kryten.1480 > udp 16
> The server however, never replies. When pinging the broadcast address, the
> ip address of the interface replies as shown below but none of the aliased
> addresses reply to the broadcast ping. Is this normal behaviour? Should
> aliased addresss reply to pings?
> 64 bytes from icmp_seq=2 ttl=255 time=0.0 ms

When pinging the main IP address should answer. This is
the same as when pinging Check your firewalling rulesets,

IP aliases in BSD are defined as follows:

 - a.b.c.d/ if there is one "main" address in the same
network (which will respond to broadcasts)
 - a.b.c.d/ (or something else) if there are no other
addresses in the same network

In Linux, all aliases can be defined as below and they "just work".

Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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