Subject: LL usage example: LL-only homenetwork with single global address + NAT

From: Markku Savela <[email-masked]>
Date: Thu, 13 Feb 2003 00:40:09 +0200

This not related specifically to any issue, but I just thought to
remind of this potential usage of Ipv4 link local (probably this has
be mentioned here):

 - a home network with multiple machines (printers and maybe others)

 - nodes at home network are LL only (automatic configuration, just
   plug in the devices). Easy to use.

 - then they get link to internet, but the nasty ISP gives only one
   global IP-address.

Thus, the user gets

 - a gateway router perfoming the ugly NAT service for outbound
   connections

Above configuration would "break" a few points that have been
discussed here:

 - nodes DO NEED to packets with LL-source and global destination to
   the NAT/Router/Gateway for FORWARDING.

 - LL-only nodes need to install default route for the gateway (does
   rendezvous have a feature for this: find the default router?).

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From: Keith Moore <[email-masked]>
Date: Wed, 12 Feb 2003 18:10:45 -0500

On Thu, 13 Feb 2003 00:40:09 +0200

>    plug in the devices). Easy to use.

easy to use, and dysfunctional.  when vendors make broken devices you
cannot expect them to work well.

>  - then they get link to internet, but the nasty ISP gives only one

not something that this group can fix.  IPv6 helps a lot, and it already
has a good solution for configuration.  local router can support IPv6
and IPv4+NAT on local net, native IPv6 or IPv4+6to4 or Teredo on
external connection.  IPv6 device configuration already works better
than v4LL.

>    the NAT/Router/Gateway for FORWARDING.

no they don't.  if anything, nodes on such a network should get routable
(RFC 1918) addresses from the evil NAT's DHCP server.  as bad as it is,
it's better than trying to figure out how to make nodes originate
traffic with an external destination and an LL source.

this just illustrates that LL-only nodes are a bad idea.

---

From: "Philip Nye" <[email-masked]>
Date: Wed, 12 Feb 2003 23:35:01 -0000

> this just illustrates that LL-only nodes are a bad idea.

And that LL addresses are not just an autoconfigured equivalent of 1918
addresses and do not have the same functionality.

Philip

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From: Robert Elz <[email-masked]>
Date: Thu, 13 Feb 2003 17:24:32 +0700

Date:        Thu, 13 Feb 2003 00:40:09 +0200
    From:        Markku Savela <[email-masked]>
    Message-ID:  <[email-masked]>

  |  - nodes DO NEED to packets with LL-source and global destination to
  |    the NAT/Router/Gateway for FORWARDING.

If this was ever to actually happen (I suspect that switching to use
1918 addresses on the internal link is what would normally be expected,
the NAT/Router/Gateway normally does DHCP as well...) then the solution
for this would be for the NAT/Router/Gateway to also proxy ARP.

Then the end node believes that it is communicating directly with the
destination, and not forwarding through a router, and no rules are broken.

Also ...

  |  - LL-only nodes need to install default route for the gateway

would no longer be true.

kre