[wplug] Networking?

[Christopher DeMarco]

On Tue, Oct 18, 2005 at 07:18:29PM -0400, Zach wrote:

> I've been looking at DSL offerings and have seen various ISPs use
> the terms "static IP", "public IP" and "static routable IP"? Are
> these all referring to the same thing? I thought all IPs were
> routable whether static or dynamic. Am I missing something? :-)

Yes, they're all the same.

Yes, you're missing something :b "Public IP" is "publicly routable",
i.e. there is at least one route between it and every other
[properly-configured] public network on the Internet.  In other words,
you can run a public service (web server, email server, etc.) on a
public IP address.

Most "consumer-grade" accounts give you a "private" or "non-routable"
IP address - this is an address within a special block reserved by the
IANA (stfw) for INTERNAL, NON-PUBLIC addresses - in all but very
special cases routers will never pass traffic between these private
addresses and the Internet.  This class of addresses is most-often
referred to as the RFC 1918 private address space (stfw); it was
allocated specifically to allow folks to number their internal
networks without having to worry about address collisions.  When
you've got RFC 1918 addresses you need a NAT firewall (stfw) to
re-write your packets using public addresses.  So if your ISP gives
you private addresses, you can bet that somewhere upstream of you is a
NAT box doing the translation to public addresses - if you've been
allocated public addresses, you're routed directly.

"Static" vs. "dynamic" simply refers to whether your ISP-allocated IP
address[es] are always the same or are dymically allocated.  The
upshot here is that with a dynamic address you've got to go to greater
lengths to reach your network from the outside world - you've got to
(a) find out your IP address (which if it's in the RFC 1918 space can
be a bit tricky) and (b) publish it using one of the dynamic DNS
services e.g. dyndns (stfw).


> On a related note does anyone know of a good open source geared
> book/website/PDF on learning networking? I'd like to learn wireless

The Linux Networking HOWTO at http://tldp.org is pretty good.

O'Reilly's __TCP/IP Networking__ (I think that's the title) is excellent.

The canonical work on the topic is W. Richard Stevens' __TCP/IP
Illustrated Vol. 1__, which will give you more detail than you
probably want, but it's *the* authoritative text.  If you're not
interested in disassembling IP packet headers it's probably overkill.


> classical nuts and bolts side first. It would have to be networking
> on the cheap since I can't afford to buy CISCO routers, PIX firewall
> etc. to learn on :) I know a little but want to learn much more

You don't need anything commercial at this point; a bunch of castaway
beige boxes running Linux, a carton of cheapie 10/100 NICs, a medusa
of CAT-5, and some switches/hubs and you've got a servicable lab.


-- 
Christopher DeMarco <cmd at alephant.net>
Alephant Systems (http://alephant.net)
PGP public key at http://pgp.alephant.net
+1-412-708-9660
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
Url : http://www.wplug.org/pipermail/wplug/attachments/20051017/8b188ab4/attachment.bin