[ILUG] Ubuntu networking questions

[Paul Jakma]

On Thu, 23 Feb 2006, Colm MacCarthaigh wrote:

> Sub-interfaces can be bonded to for example, which allows 
> applications to listen on a sub-set of addresses, or to prefer a 
> specific source address, without having to specify a list of which 
> addresses. This is probably the biggest effect/difference.

This doesn't ring true to me.

Selecting "interfaces" is typically done either by local address or 
else by ifindex (see, e.g. the multicast sockopts). I can't think of 
a sockopt that passes in or back device labels[1].

Addresses with labels do not have a distinct ifindex, you could only 
ever 'pick' them by address. For which it doesn't matter whether or 
not the address has a label.

'virtual interfaces' simply don't exist as far as userspace ought to 
be concerned, not on Linux, not on BSD.

The only system I know of where additional addresses actually /do/ 
come wrapped up with additional interface structures is Solaris. (And 
even there the sanest way for userspace to deal with it is to think 
of it as behaving just like BSD - simply because other parts of 
Solaris kernel do so, e.g PF_ROUTE - if you intend to make use of 
it.).

1. I can think of ioctls where the 'label' matters, but only on 
Solaris.

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
Fortune:
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