"Reserved" IP vs. manually-assigned?
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Subject Author Date
"Reserved" IP vs. manually-assigned? SparkyGuy 07-26-2007
Posted by Rod Dorman on July 27, 2007, 2:38 pm
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>> What's "DMZ"?
>
>It means 'demilitarized zone'.
>The concept is that the router will take specific internet requests that it
>receives,
>such as port 80 (web servers) and forward these requests to one specific
>machine.
> This way you can run a web server on that one machine, and make it open
>to the public without placing your whole network at risk.

I would have described a DMZ as a network (not limited to only one
machine) segment outside the firewall protecting your internal LAN.

The main point being if your web/ftp/whatever server is compromised
your internal LAN is still protected.

--
                                        -- Rod --
rodd(at)polylogics(dot)com

Posted by Bill Kearney on July 31, 2007, 8:32 am
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> The main point being if your web/ftp/whatever server is compromised
> your internal LAN is still protected.

Unfortunately too many folks configure their firewall to let DMZ devices get
into the internal network. Thus compromising a DMZ device often provides an
*easier* attack vector than taking the firewall head-on. If you're going to
use a DMZ setup, make sure that whatever firewall rules exist for it (and
programs running on it) have VERY strict controls on where it can connect
internally (if at all).


Posted by Bill Kearney on July 31, 2007, 8:29 am
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> *DHCP requires you to physically go and find a computer's IP address.* If
> you want to ping or remote into a computer, you have to go and finds it's
> address. With a static IP, you can ping into the name of the computer (if
> you have a text file of all the computer names).

This is incorrect, or at the very least, incomplete. You can setup DHCP to
reserve addresses based on MAC address. The same hardware will get the same
DHCP lease every time. Yes, if you change the hardware in the computer it
will require configuring a new lease reservation on the DHCP server. But
you'd also have to manually reconfigure it if it was static.

When using a Windows Active Directory domain the DHCP server is integrated
with DNS. So the name of the Windows machine can be automatically
propogated into the internal DNS. It's also easy to use the GUI to check on
what addresses are allocated. Some text-based DHCP servers do not make it
this easy and also wonn't integrate with DNS.

But in either case it's a simple matter of speaking with the user and asking
them to run the command "ipconfig" or "ifconfig" if they're not on windows
box (linux, etc...) to get the unit's current IP address. So it's not like
you have to lay hands on it directly.

> *Some applications can only use a static IP* Lets say you have a server,
> video camera, or need to remote into a computer on your LAN from the
> outside. You need to set Network Address Translation (NAT) in your DSL
> modem and/or router. If you computers are set to DHCP, your computers'
> addresses may be unpredictable.

Again, incorrect if the device CAN use DHCP. Setup a lease for that
hardware MAC (Media Access Control, not Macintosh) address and it will
always have the same one. Most devices that do not have a user interface
(no buttons, no screens) will default to using DHCP out of the box.
Manually changing this to something else only complicates your support
efforts if/WHEN you have to replace the unit. Otherwise you just read the
MAC address off the back of the box when installing it and setup a lease for
it.

I do find it useful to setup the DHCP ranges starting above 64 or so. Only
to lease the lower addresses free for devices that actually DO require
static ones.


Posted by DLR on July 31, 2007, 3:38 pm
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Bill Kearney wrote:

> But in either case it's a simple matter of speaking with the user and asking
> them to run the command "ipconfig" or "ifconfig" if they're not on windows
> box (linux, etc...) to get the unit's current IP address. So it's not like
> you have to lay hands on it directly.

"simple matter"

Yeah, right. ;)

Posted by Gerard Bok on July 26, 2007, 2:14 pm
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On Thu, 26 Jul 2007 08:58:35 -0700, SparkyGuy

>Netgear RP614 router.
>
>Under the LAN configuration menu there are, among others, options for DHCP,
>and Manually-assigned IP addresses. Under DHCP there is also a table for
>reserving IP addresses. This feature allows you to use DHCP to dynamically
>assign addresses except that for each MAC address you specify, the router
>will assign a particular IP (specified by you).
>
>Is there any difference between reserving an IP address under DHCP, and
>manually assigning one?

Yes. If you instruct your DHCP server to issue 'static'
addresses, you still get all the benefits of using DHCP.

If you decide to assign static addresses, you'll need to visit
all hosts if you want to change a simple thing like the DNS
server :-)

--
Kind regards,
Gerard Bok


other useful resources:
The Federal Communications Commission (FCC)
Telecommunications Industry Association
Electronic and Software Security Products and Services
International Telecommunication Union

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