Re: 2 ip numbers on 1 computer

Steve Winograd [MVP] wrote:
In article <uiISno9SHHA.4276@xxxxxxxxxxxxxxxxxxxx>, "Jack
\(MVP-Networking\)." <Jack@xxxxxxxxxxxxxxxxxxx> wrote:
Hi

You can assign an alternative IP, as mentioned in Steve's post.

However a choice has to be made which one you are using, you cannot use one card with two IPs at the same time.

Putting a second card in your computer and using it with a second IP does
nothing either as far as Internet surfing goes.

Two external IPs can be useful in special situations when you use few
devices/computers and one device has to be directly on the Internet while
the other computers are behind a Router, or similar concoction.

As matter of fact, the multiple dynamic IPs given by some ISPs is useless in
almost all cases since it is not providing more Bandwidth (speed), and it
acts against the concept of having a private LAN.

Jack (MVP-Networking).
XP has an "Alternate Configuration" in the TCP/IP properties, but
that's not what I mentioned. Alternate Configuration lets you specify
a static IP address to use if no DHCP server is available.

The configuration that I mentioned gives two static IP addresses to a
single network connection, and you can use both IP addresses at the
same time. The two IP addresses have to be in different subnets,
though, to be useable.
There is a focus to this discussion.
As far as I can understand the intention of the OP is to use it with one available Internet connection.
Connecting one computer with two NICs to a single Broadband modem (with a switch or whatever) does not yield the results that the OP is looking for.
Jack (MVP-Networking).

The OP mentioned getting 5 IP addresses from his ISP. If they're
static, which is possible, he can assign two of them to a single NIC.
I don't understand his question well enough to know whether that will
accomplish what he wants.

However, I feel that your statement "you cannot use one card with two IPs at the same time." is too broad, because I had
already pointed out a way to do exactly that in some circumstances.

Steve,

I understand _how_ to add multiple static IPs to a single NIC, but _why_
would one do this, and how does it work?

If a NIC has multiple IP addresses assigned, what gets placed in the "source IP address" portion of the IP header of packets sent by that NIC? The top-most IP address in the list? I wouldn't think that it would duplicate each outgoing packet for each separate IP address.

I assume that if I configure my NIC with:

192.168.0.101 and
192.168.1.101

I can _receive_ packets from other computers on either the 192.168.0.x subnet or the 192.168.1.x subnet (without the need for a router).

What happens if my 2-IP address NIC transmits packets? Who can receive them (without going through a router)?

--
Lem MS MVP -- Networking

To the moon and back with 64 Kbits of RAM and 512 Kbits of ROM.
http://en.wikipedia.org/wiki/Apollo_Guidance_Computer
.

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