I believe the dhcp spec says you must renew after half of your lease
time has expired.  So, if your lease is 7 minutes, your client will have to
renew after 3.5 minutes.  This is a fairly short time frame, it's possible
not all the network glue that dhclient pastes into your configuration gets
completely settled between renew cycles.  Typical lease times are between
15 minutes and 24 hours.  For really stable environments, lease times of a
week are quite common.  A week is what I use on my home systems, and that
just works for everything I've ever connected, laptops running Windows,
WIFI IP phones, Tivo boxes, other strange stuff.
So, try upping the lease time, and see if that changes the behavior you
get.  I'm not sure why Steven's suggestion works, but it does hint at a bug
somewhere, either in dhclient, or our routing code.
-Brian
On Nov 8,  5:06pm, chandru wrote:
} Subject: Re: Can't assign requested address
} On 08/11/05, Brian Buhrow <buhrow@lothlorien.nfbcal.org> wrote:
} >         What's the lease time on your dhcp address?  What happens if you
} > assign an address manually?  Can you telnet to a port on your MAC
} > successfully?
} >         Two possibilities come to mind:
} >
} > 1.  The lease time on your dhcp address is short enough that dhclient is
} > dropping it before you can connect to anything.  This seems highly
} > unlikely, given your output, but it occurs to me, so I offer it up for what
} > it's worth.
} 
} I just checked and it is about 7 minutes. Quite short I guess. Is this
} usual? I don't know. What is the recommended time for a DHCP server.
} Since this is my home setup I guess I can put it up a bit more.
} 
} > 2.  More likely, the problem is actually on your MAC.  I think if you were
} > to run tcpdump on your fxp0 interface while trying to connect to an outside
} > address, you'd find that the MAC sends back a response which causes errno
} > to be set to 49, which is throwoing you off the scent of the problem.  the
} > MAC is doing the NAT, right, is the ADSL router also doing NAT?  Are you
} > somehow getting tripped up by double NAT?
} >
} >         In any case, a little time with tcpdump on the fxp0 interface on your
} > NetBSD box will, I think, be quite enlightening.  It will answer the
} > question, is the problem local or remote, where remote is the MAC, and
} > remote is in the NetBSD box itself.
} > -Brian
} 
} I did run ethereal on the Mac, but I couldn't actually see any traffic
} other than DNS queries. But Steve's suggestion helped. I manually
} deleted and added the default route and it worked straight away. Still
} a bit of a mystery how it worked!
} 
} thanks for responding.
} Chandru
} 
>-- End of excerpt from chandru