Re: Cisco VPN client gives the following status: Not Connected

Walter Roberson wrote:

:There is no such thing as unroutable IP address. Even 127.0.0.1 is
:routable. You possibly meant IP address from private and reserved
:address spaces.
You would appear to be incorrect on both points.


Well, not exactly:

"RFC 3927 - Dynamic Configuration of IPv4 Link-Local Addresses"
   This document uses the term "routable address" to refer to all valid
   unicast IPv4 addresses outside the 169.254/16 prefix that may be
   forwarded via routers.  This includes all global IP addresses and
   private addresses such as Net 10/8 [RFC1918], but not loopback
   addresses such as 127.0.0.1.


Please note phrase "this document".

Process of "routing" a packet, is finding longest destination match in
routing table and queuing this packet on the looked up destination
address. This process is not specially different for any public IP
(62.111.150.246 being my actual IP for example) and for any from
the RFC1918 *if* we let things like keeping Internet clean and filtering
private address spaces aside. Router gets a packet, look ups the
RIB for longest-prefix match and forwards packet, if nothing gets in
the way.

It's true of course, that most of the systems usually treat 127/8
traffic in a special way on a low-level, but it's still
routable - meaning it can be found in a RIB and it can be used.
And I don't know any (I've just browsed NetBSD/OpenBSD/FreeBSD and
Linux kernel sources just to be sure) that treats RFC1918 lookups
differently than any other destination addresses.

And, as far as we're speaking about that - many ISPs still don't
filter RFC1918 address space, and You can still see 10/8, 172.16/12,
192.168/16 or even sometimes 169.254/16 packets wild in the Internet.
If they wouldn't be routable, how could they appear in Internet?

   127.0.0.0/8 - This block is assigned for use as the Internet host
   loopback address.  A datagram sent by a higher level protocol to an
   address anywhere within this block should loop back inside the host.
   This is ordinarily implemented using only 127.0.0.1/32 for loopback,
   but no addresses within this block should ever appear on any network
   anywhere [RFC1700, page 5].


....yes, and quoting my post: "Even 127.0.0.1 is routable" means,
127/8 network is usually in the RIB. You don't have it?

As far as speaking about what is 'private address space' and
'public address space' please see RFC1918:

  http://www.faqs.org/rfcs/rfc1918.html

And You'll notice official terminology is 'private/public address
space', not 'routable/not routable IP address'. RFC3927 is using
the term 'routable' to differentiate link-level address space of
IPv4 (169.254/16) from other address spaces. Only other place within
RFC/BCP etc. besides RFC3927 I see term 'routable IP address' is with
suffix 'globally' which makes obvious sense but You didn't add it in
Your post.

However, I do think this discussion is purely academical - I'll just
made a comment about terminology that's all. I won't try to push my
humble opinion down Your throat ;)

Regards,
--
this space was intentionally left blank    |            Łukasz Bromirski
you can insert your favourite quote here   |        lukasz:bromirski,net
.