Re: panic.log on Intel?
Re: panic.log on Intel?
- Subject: Re: panic.log on Intel?
- From: Peter Lovell <email@hidden>
- Date: Fri, 20 Oct 2006 14:19:53 -0400
On Oct 19, 2006, at 10:59 AM, Derek Kumar wrote:
As I noted the last time this came up (and that thread involved the
same participants, as I recall :), RFC 1812's router forwarding
algorithm requires compliant implementations to forward packets to
the appropriate interface (where the most specific or "longest"
network prefix matches that of the packet's destination) regardless
of the origin of the packet; empirically, routers at places such as
Apple, Oracle, Cisco, nVidia, MIT and my comcast cable modem don't
seem to have any trouble doing this. Certain installations aren't
configured to do this, but unless you encounter this configuration,
I wouldn't make any assumptions about the necessity of a second
subnet etc.
Hi Derek,
yes - the same participants !
I did some investigation after our earlier discussion. Since I don't
write router-type code, I asked a Mac developer who does it for a
living.
He commented ...
>Not forwarding packets back out the same interface they arrived on is
>actually a feature of many advanced routers. Open Transport had three
>IP Forwarding settings: (1) off; (2) automatic; and (3) forward. The
>"automatic" setting was added to provide just the behavior above which
>is generally seen as more robust.
>
>The reasons are:
>(1) The packet can be delivered directly and the administrator may
>prefer the router to send an ICMP redirect to tell the sender to do so
>as this makes better use of the routers interface bandwidth.
>(2) A packet may arrive at the wrong interface due to a network
>configuration error, unintended routing loop, or malicious attack. By
>not forwarding such packets, we prevent a common class of packet
storms
>or routing errors that might escalate into more serious problems.
This
>is similar to the concept of "Split Horizon Routing" <http://
>www.webopedia.com/TERM/S/split_horizon.html>
>
>Advanced routers should provide an option to select the RFC compatible
>forwarding behavior, but the "automatic" mode has become so widely
>deployed and recommended, I'm not surprised to hear some small routers
>just implement it by default.
The default gateway at my day-job is a CheckPoint firewall and it is
indeed configured this way.
I also tried three of the small routers commonly used for home or
SOHO, from Linksys, D-Link and an older MacSense. None of these would
forward a packet to the incoming interface.
Regards.....Peter
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