Re: Can't Access Printer!!!

On Tue, 15 Jul 2008 04:53:36 -0400, gmark wrote
(in article
<2aec2d29-9ce9-4284-8f5e-44a0d043871c@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>):

On Jul 15, 12:10 am, J.J. O'Shea <try.not...@xxxxxxxxxxx> wrote:
On Mon, 14 Jul 2008 23:26:53 -0400,gmarkwrote
(in article
<a3f91769-4b30-4963-bd3f-fa6c9d15e...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>):



Wow -- thanks! Some questions below--vvv

On Jul 14, 6:11 pm,gmark<gm...@xxxxxxx> wrote:
On Jul 14, 5:39 pm, Chris Ridd <chrisr...@xxxxxxx> wrote:

On 2008-07-14 22:02:46 +0100,gmark<gm...@xxxxxxx> said:

On Jul 14, 9:00 am, J.J. O'Shea <try.not...@xxxxxxxxxxx> wrote:
On Mon, 14 Jul 2008 04:54:00 -0400,gmarkwrote
(in article
<5015038f-5333-4786-8381-a22be41bf...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>):

I've got a cable modem which goes to a router, which is, in turn,
connected via ethernet cables to a hub upstairs which goes to two
macs.  My macbook is in the downstairs office, and connects to the we
b
via an airport link.  That link -- via a Netgear WPN824 -- connects
via ethernet cables to the upstairs hub.

I used to be able to access my Color Laserjet HP 2605 flawlessly, but
no more.  I thought having the entire IP address of theprinterwould
allow me to access it, regardless of the IP address theprinterwas
assigned after resetting. Now, jobs just get rejected from my Macbook,
even though the computers upstairs have no problem accessing the
printer.

Any ideas?

What is the _exact_ error message?

All the information is below.  I don't see why I can't access this
printerwith the full IP address -- I suppose the router is the
problem -- maybe the subnet mask?  I really appreciate any help.  I've
been unsuccessful reading all sorts of IP troubleshooting material off
the web, so it might be something basic and trivial enough that they
just don't bother touching on it.  Don't hold back any details, no
matter how obvious it may see  to you.

Thanks!! (data below)

[...]

Main Router (off cable modem)
-------------------
MAC Address:  00-15-e9-79-ac-f6
IP Address:  192.168.0.1
Subnet Mask:  255.255.255.0
DHCP Server:  Enable

[...]

Color Laser HP 2605dn (off Main Router)
-------------------
IP Address:  169.254.23.24
Subnet Mask:  255.255.0.0
Default gateway:  169.254.23.24

There's your problem - theprinter'susing a link-local IP address that
is outside of the subnet of your main router, so it is routing
yourprinterconnection attempts to your ISP instead.

I would reconfigure theprinterso that it has a 192.168.0.x IP address.

I tried that -- last set it to 192.168.0.103/102/148 -- none of which
worked. Is it possible that thatprinter(or some attached system) has
to explicitly do something to make the system aware of the new IP?
I'd heard that theprinteritself had to request a DHCP update.

If I have the actual, complete IP address of theprinter(as I do,
obviously), why can't the router find thatprinter?  Does the router
automatically limit accesses to some subnet, and is that subnet
defined by the mask?  And if so, does the router or theprinterhave
to be forced to make an update?

Thanks!

Mark

As an aside, I've been looking over the web for a good summary of IP
networks -- DHCP, NAT, etc. -- and it doesn't seem there's one to be
found.  They all seem to be missing the "summary" part.

Anyone have any recommendations?

Thx!

DHCP is fairly simple. A DHCP server automatically assigns IP addresses to
nodes (printers, computers, etc.) attached to it, by Ethernet or by
wireless.
These addresses are assigned from out of the DHCP pool. Private networks,

So the DHCP server (one of the computers always, or could it be in the
router?)

You could start up a DHCP service on a computer, but it ould be easier to
just use the built-in service that ships with the router.


keeps track of the IP addresses it assigns a device?

yes.

And the device
also remembers
this.

The device gets an IP from the first DHCP server it sees. This is why it is a
Very Bad Idea(tm) to have two or more DHCP servers on a single subnet.


such as yours, usually use DHCP pools from one of the three private address
ranges: Class A, 10.x.x.y, where 'x' is 0 to 255 and 'y' is 1 to 254; Class
B
172.16.x.y to 172.31.x.y, and Class C, 192.168.x.y. That's one Class A
range,
16.8 million IPs, plus 16 Class B ranges, 65 thousand IPs each, and 256
Class
C ranges, 254 IPs each. Typically the router is assigned either the very
first or the very last available IP, something like 192.168.0.1 or
192.168.0.254. (192.168.0.0 is the 'network' IP, and is reserved;
192.168.0.255 is the 'broadcast' IP, and is also reserved.) You can restrict
the size of the DHCP pool; on my network, I have blocked off the first 50
IPs, for use as fixed IPs if necessary. (This is called 'excluding' IPs.)
You
can tell the DHCP server to always give a certain IP to a certain device;
this is called 'reserving' an IP. On my home net, my server and my network
printers are all assigned fixed IPs from the excluded block. My workstations
all have reserved IPs. (The office net also has the servers and printers
given fixed IPs, but there's no way that I'd go to the trouble of reserving
IPs for all the workstations, there's far too many of them.)

If I were you I'd exclude a block of IPs from the DHCP pool generated by
your

This is done via the subnet mask?

Not quite. The subnet mask definles your network. In classical TCP/IP
networks, what's used is ClassfulAddressingg: Class A, B, C. There's also D
and E, but you'll never see them. The subnet mask for Class A is always
255.0.0.0, for B is 255.255.0.0, and for C is 255.255.255.0. The '255' parts
identify the network part of the IP, the '0' parts identify the host part. IP
v4 addresses are specified using 'dotted decimal' notation: 10.0.0.1, for
example. There are four octets, written in base 10 (decimal) and separated by
dots. The classes are defined by the first octet. Class A is 1 to 126, 127 is
reserved, Class B is 128 to 191, Class C is 192 to 239. That means that in
all the world there are a total of 126 Class A networks, and one of those,
the 10.x.x.y network, is held back as a private network.

The 172.16.x.y through 172.31.x.y networks are Class B networks which are
private nets. The 169.254.x.y network is reserved for APIPA. The 127.x.x.y
network is, officially, a Class A, but is never used for anything but
loopback and is a special case. The 192.168.x.y networks are Class C private
networks.

Class A networks have 16.8 million IPs. (16 million, 770+ thousand, actually,
but who's counting?) Class B networks have 65,000 IPs. (65,000 and some
change, actually, but again who's counting?) Class C networks have 254 IPs.
(256 minus the network and broadcast IPs)

It is entirely possible to use different subnet masks and a technique known
as Classless Addressing. This gets complicated real fast. Unless you know
what you're doing and have a good reason, just stick with Classfull
Addressing and have done. Screwing around with the subnet masks is a good way
to split your net into lots of different nets, which may not be what you
want.


Netgear, and assign one IP to theprinter, but would let the Netgear hand out
IPs using DHCP to all your computers.

Any reason not to used fixed IPs for the computers?

If you have only a few, then no problem. Once you get past a couple dozen
machines then remembering or writing down the IPs for all of them gets old
fast. Having the system assign IPs is easiest.

Seems if I wanted
to communicate
with them, I'd like them to be static so I could remember them. Or do
people generally
use symbolic addresses (e. g., <computer-name>.local ) ?

That usually works.


NAT is also fairly simple. What it does is it uses your router so that your
entire local network pretends to be just one IP on the Internet. The router
has a WAN IP (in your case, 24.15.121.159) and is set up as a gateway using

Where did that IP address (24.15.121.159) come from? The standards
docs?

That IP is the one assigned you by your ISP.


the address 192.168.0.1 on your local net. Any device which is on the local
net and which knows the address of the gateway can use the gateway to
connect
to the Internet. The Internet sees only the gateway. You could have all 254
nodes of a Class C private network set up behind the gateway, and the only
evidence that might point that way would be the traffic going in and out of
the gateway. The router knows which local device made which request, so it

Where is the data to identify the request a particular packet is
associated with?
Somewhere in the header?

Yes.


knows where to send the reply when it gets it.

It seems to me that one of the computers on my network should be
providing the
DHCP functionality and is turned off. (Or perhaps the router used to
provide this?)

It would probably be the router.


Now, if the laser printer used to request a DHCP assignment, it may
also have been
disabled inadvertently.

Mark

--
email to oshea dot j dot j at gmail dot com.




--
email to oshea dot j dot j at gmail dot com.

.

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