Default gateway - wrong interface. !

[Gleb Smirnoff]

On Sun, Feb 19, 2006 at 03:14:35PM +0000, Josef Karthauser wrote:
J> I'm guessing that this is a bug (or feature!).

This is not a bug, nor a feature. This is a feature, that hasn't
been implemented to the end.

Historically, the routes in kernel were static. And they are static
now. Historically, BSD won't permit you to install same IP addresses,
or even addresses in the same subnet, on different interfaces. Now,
FreeBSD permits addresses in the same subnet. But route entries are
still static, and aren't reconfigring when an interface changes its
flags.

J> I've got a machine with a wlan interface (iwi0), with an ipv4 network
J> address and a default gateway.  I also have an ethernet card in the same
J> machine (em0) with the same IP address.  The idea is that I can bring
J> the wireless down, and the wired interface up to get fast transfers when
J> approriate, and be wireless the rest of the time.
J> 
J> That works fine, apart from the default gateway:
J> 
J>     # ifconfig iwi0 down
J>     # ifconfig em0 up
J>     # arp -ad
J>     # netstat -rn
J>     Internet:
J>     Destination        Gateway            Flags    Refs      Use  Netif
J>     Expire
J>     default            87.74.4.33         UGS         0      123   iwi0
J>     87.74.4.32/27      link#3             UC          0        0    em0
J>     87.74.4.33         00:90:d0:02:3f:16  UHLW        2        1    em0
J>     87.74.4.34         00:d0:b7:88:c8:20  UHLW        1  1191414    em0
J>     127.0.0.1          127.0.0.1          UH          0        2    lo0
J> 
J> Notice, the local subnet is off the em0, but the default route is still
J> wired off the iwi0.
J> 
J>     # route delete default
J>     # route add default 87.74.4.33
J>     # netstat -rn
J>     Internet:
J>     Destination        Gateway            Flags    Refs      Use  Netif
J>     Expire
J>     default            87.74.4.33         UGS         0      123   iwi0
J>     87.74.4.32/27      link#3             UC          0        0    em0
J>     87.74.4.33         00:90:d0:02:3f:16  UHLW        2        1    em0
J>     87.74.4.34         00:d0:b7:88:c8:20  UHLW        1  1191414    em0
J>     127.0.0.1          127.0.0.1          UH          0        2    lo0
J> 
J> The default route is _still_ off iwi0; but should be off em0.
J> 
J> There's obviously something dumb doing on here.  Why does the default
J> route have to be nailed to an interface?  It's clear that 87.74.4.33 is
J> available from em0 as far as the routing table is concerned.
J> 
J> Joe



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