Date: Wed, 08 Aug 2001 16:32:01 -0400 From: Mike Tancsa <mike@sentex.net> To: Jun-ichiro itojun Hagino <itojun@iijlab.net> Cc: freebsd-net@freebsd.org Subject: Re: gif MTU of 1280 ? Message-ID: <5.1.0.14.0.20010808162550.0433abb0@marble.sentex.ca> In-Reply-To: <20010808202655.893BF7BC@starfruit.itojun.org> References: <mike's message of Wed, 08 Aug 2001 16:18:53 -0400. <5.1.0.14.0.20010808161744.0495abf0@marble.sentex.ca>
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At 05:26 AM 8/9/01 +0900, Jun-ichiro itojun Hagino wrote:
> >But where would the PMTU source address come from ? If someone is rejecting
> >all RFC 1918 space at their border, if a ICMP message originates with such
> >source address, would this not be problematic ?
>
> I don't understand what you are trying to discuss. diagram please.
>
>itojun
172.16.1.1/24 <--> 10.0.0.1/30 - - - 10.0.0.2/30<--->192.168.1.1
With 192.168.1.1 and 172.16.1.1 being non RFC 1918 addresses in this
example and the 10.0.0.1 IPs being the internal addresses.
Lets say a machine (216.136.204.21 wants to get to 192.168.1.1, and it
comes in via the public gateway 172.16.1.1. To get to 192.168.1.1, it must
be fragmented. The question is, when the ICMP message is sent out, with
what source address does the packet leave ? e.g. if 216.136.204.21 is
configured to ignore all traffic from the RFC 1918 space, and the ICMP
message goes out with a source address of 10.0.0.1 or 10.0.0.2, then
216.136.204.21 will never hear it.
---Mike
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