Hi,

On Wed, Nov 22, 2006 at 08:10:18PM +0100, Hubert Feyrer wrote:
> On Wed, 22 Nov 2006, David Young wrote:
> >    -I ifaddr
> >            Send multicast datagrams on the network interface specified by
> >            the interface's hostname or IP address.
> 
> How about:
> 
>  -I ipaddr
> 	Send datagrams on the network interface specified by the
> 	interface's hostname or IP address, 

Hmmm, that's not actually what it's doing ("send out on *that* network
interface").  It's just using that IP address, and sending out the
packets via the normal routing table (unless "-r" is set).

More like:

-I ipaddr
       Send datagrams using the specified source IP address.  This option
       can be used to force the source address to be [...]

> and use that as the source address of outgoing packets. 
> On hosts with more than one IP
> 	address, this option can be used to force the source address to be
>  	something other than the IP address of the interface the probe
> 	packet is sent on. If the IP address is not one of this machine's
> 	interface addresses, an error is returned and nothing is sent.
> 
> (taken mostly from FreeBSD; someone please confirm if the error handling 
> is actually true!)

Yep, the error handling works:

gert@delta.greenie.net:/home/gert$ ping -I 96.0.16.1 195.30.0.1   
...
64 bytes from 195.30.0.1: icmp_seq=0 ttl=61 time=1.553 ms
...
gert@delta.greenie.net:/home/gert$ ping -I 96.0.16.2 195.30.0.1
ping: Can't set source interface/address: Can't assign requested address

(96.0.16.1 is an alias on lo0, used for routing/IPSEC tests)

gert

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Gert Doering - Munich, Germany                             gert@greenie.muc.de
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