Obtaining IP address automatically vs setting it manually?

[Guest]

What are advantages-disadvantages of setting IP addresses manually against
obtaining them automatically for a basic home network of three computers and
a hub?

 

[Dave]

What are advantages-disadvantages of setting IP addresses manually against
obtaining them automatically for a basic home network of three computers and
a hub?

well, in order to obtain it automatically you have to have a dhcp server
somewhere. you say you have 3 computers and a hub, that would mean one of
the 3 computers would have to be the dhcp server unless you have some other
connection to an isp that will assign you 3 addresses.

if you assign them manually then you are responsible for them getting all
the right addresses.

 

[Kerry Liles]

If you don't have a DHCP server, for Windows-based machines
APIPA comes into play:
the machines auto-assign themselves an address in the reserved
range:
169.254.0.0 - 169.254.255.255

This Automatic Private IP Addressing scheme lets machines
communicate locally without the need to statically set IP
addresses and subnet masks. This obviously may not be suitable
for everyone.

In fact, when I see an IP address like 169.254.1.1 I almost
automatically think "oh, DHCP failed" - this even though I have
seen people who have deliberately set up their network that
way...

You can Google for APIPA and read more about it... I suppose the
one thing it has going for it is the lack of human
involvement... hehe

 

[Guest]

Thanks. In my case the hub is also a router which acts as a DHCP server.

From what yopu are saying, the manusl static setting has the only satback -
the need for manual job.
Is it a big deal to set is manually in a network of 3 PCs?
Once it is set, it has not to be reset, unless I change the system
configuration?

 

[Kerry Liles]

Setting the IP address manually is not big deal - you uncheck
the "obtain an IP address automatically" and then assign your
own IP and appropriate subnet mask. For local networks you
should use address ranges reserved for that purpose:

10.0.0.0 - 10.255.255.255 /8
172.16.0.0 - 172.31.255.255 /12
192.168.0.0 - 192.168.255.255 /16

I presume in all this thread we are talking about computers that
are NOT conected to the outside world? If your hub is also a
router - it's a router. Hubs are a lot stupider <g>

If your router provides DHCP services to the machines behind it,
then I would suggest letting it do it's thing. I presume the
router also provides NAT (network address translation) - that
allows the router to properly associate traffic to/from the
Internet (or the Wan connection on the router) with the machines
behind the router. In this case (letting the router do it's
thing) you don't have to contend with DNS settings and other
things - the router handles that too.

 

[aa]

Actually the hub/router (Vigor2600x) happened to be an ASDL modem and it
indeed is connected to the Internet.
Do you mean that in this case I should not assign static addresses?

 

[Kerry Liles]

Well, I am guessing that the Vigor2600x is an ADSL modem with
built-in router capabilities, so in that case I would let it
manage everything. If you start assigning static addresses on
one or more of the machine behind that device, you may find that
you have to do more than just assign the IP and subnet mask: for
example, you likely will have to fill in the information that
the router is now supplying: dns server IP addresses, domain
suffix etc.

Unless you are experiencing problems, I think you should leave
it as dynamic.

HTH

 

[Jeff Cochran]

What are advantages-disadvantages of setting IP addresses manually against
obtaining them automatically for a basic home network of three computers and
a hub?

Advantage of dynamic IP's is that you can set the config in the DHCP
server and when your TCP/IP config changes, you only change it there.
Kind of a non-issue for just three systems.

Jeff

 

[Dave]

with a router that does dhcp i would let it do its thing unless you have
some compelling reason to assign static addresses. remember also, if you do
assign addresses manually you should tell the router dhcp to not assign the
same address. this shouldn't be a big problem in a 3 computer network, but
the automatic stuff works so well most of the time its hard to justify doing
it manually.

 

[Guest]

I do experience problems, Kerry - it simply does not work, or worse, when it
works, it works unstablly and there is no sound explanations why.
I strated about 6 threads here recently, mainly on the same subject and
still cannot get a working advise. Someone from another NG sugested
swtiching to static addresses and I wanted to know more opinions

 

[Guest]

Dave, as I mentioned to Kerry above, I seem to have compelling reasons - it
simply does not work and with the present setup no-one seems to be able to
offer a solid theory of what is wrong and how to put it right.
I decides to try static addresses simply out of desperation - if it does not
work, it could not be worse.

 

[Guest]

I see. Are there any advantages of the static addresses?
I just inclined to think that with manual settings you do not have to guess
if the DHCP is screwing thing up if they go wrong?

 

[Kerry Liles]

Can you elaborate on "it simply does not work"? Can you not get
to the internet via any of the 3 pc's? Or does your internet
connectivity go up and down? etc.

 

[Guest]

All the three PS have no problems with acccessing Internet. The have
problems accessing each others filders and printers .
They show each others' shared folders, even can open some of them. But
opening the others result in
"unexpected network error" or "specified network name is nolonder available
or "The local device name is already in use"
One of the three computers cannot open anything at all exept CD-ROMs on
other computers (I made them shared).

Also I uninstalled-installed NIC driver on one of the computers and this
caused the IP addresses change on that PC and on one of the others. The
third one remained intact. So much intact that pinging other computers it
still uses their old IP addresses despite I made relevant changes in lmhosts
which use is enabled (althought I suspect that lmhosts which is a Windows
feature might not be relevant to PING command)

 

[Jeff Cochran]

I see. Are there any advantages of the static addresses?

You don't have to have DHCP.

I just inclined to think that with manual settings you do not have to guess
if the DHCP is screwing thing up if they go wrong?

Nope. It's all your fault.

Jeff

 

[DS]

I see. Are there any advantages of the static addresses?

1. You always know the IP address of a machine since it doesn't change,
ever. If your 3 PC's are on all the time, they should just about never
change with DHCP, but if they are always being turned on and off, the IP
could change between the 3. The same 3 IP's just assigned to different
computers.

2. If you have a 'service' of any type (WWW server, FTP server, you want
to remote desktop into one of them maybe), anything you'd need to add a
port map for in the router, if the IP changes, then the mapped service
won't work, unless of course the rtr see's by MAC address that the IP has
changed for the PC that has the service running and adjusts the port map
automatically. I doubt if it would.

3. If the rtr doing the DHCP is a wirless access point, it is just
another security hole. Since AP usually come in the box set up to be wide
open, if encrytion is not enabled & the AP access list by MAC Address is
not enabled & DHCP IS enabled, you're just asking for trouble.

Regards,

DanS

 

[Guest]

Will static addresses eliminate the need for ARP exchange which should
increase the speed?

 

[DS]

Will static addresses eliminate the need for ARP exchange which should
increase the speed?

ARP is ARP and DHCP is DHCP. There would be no speed increase of anything
with static addresses, other than not having to wait for a DHCP address
upon boot up.

DS

 

[Guest]

ARP maps IP address to a herdware address. If IP addresses are subject to
change, them ARP have to be run all the time?

 

[Stephanie Song [MSFT]]

When the MAC address matching an IP address is unknown address resolution
occurs. The resulting information is usually saved in an ARP table for quick
lookup in the future. The entries in the ARP table usually have timeouts
associated with them to cause refresh. Most implementations have means to
flush the ARP table via commands or equivalents.