Default route doesn't change to wireless device (ath0)

Lars Erik Gullerud lerik at
Fri Sep 9 02:24:00 PDT 2005

On Thu, 8 Sep 2005, Jon Dama wrote:

>> Bringing an interface down then back up is usually one of the "try this
>> first" operations when troubleshooting all platforms I normally work on,
>> exactly because it _does_ (normally) clear a lot of state info that you
>> don't want around to confuse you (like the ARP cache and routing table
>> entries).
> Yes but surely you'd recognize a difference between a link state change
> and issuing ifconfig ... down
> In the latter case, I expect state to be flushed.  In the former, I expect
> everything to resume when the link is restored.  Imagine having to
> manually reinit your interfaces just because some joker temporary
> unplugged your ethernet cable!

No, quite the opposite - a link state change is is when you REALLY want 
state (particularly ARP) to be flushed. If someone unplugs your ethernet 
cable, and the link subsequently returns, you have no way of knowing you 
are on the _same network segment_. You may plug out your cable and plug 
it into a different network, in which case you do NOT want old ARP 
entries to remain. I.e. the new network may use the same IP addressing, 
but obviously ARP will point to different macs - in which case you will 
get no traffic because your host will not re-ARP IP-addresses for which 
it already has a cache entry. ARP cache should _always_ flush on link 
state change.


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