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Multiple IP Address on single NIC

Last response: in Networking
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July 24, 2007 4:32:58 PM

First I want to mention I have searched this form and a number of other places to find this. Having said that there are some similar instances of this but not quite what I want to do.
I have an existing T1 using 64X12 for data with a public outside thru a pix to 192.168.0.** inside for 20 pc's
I have 25 remotes in 5 offices conecting to a Terminal Server which connects to the app server.

I have ordered comcast with 6meg down 768up to speed up our connection.

My idea: Comcast ->inside = 192.168.5.** / 192.168.5.1 GW

DHCP is turned off everywhere. All computers inside have static address

Existing T1 - TServer = 192.168.0.10 / GW 192.168.0.1
New Ccast - I want to add TServer = 192.168.5.10 / GW 192.168.5.1

However I want to do this on a single network card. The question is will this cause caos on the Lan w/ two different ipaddress on the same ethernet cable structer?
July 25, 2007 12:45:46 AM

Sound pretty complicated but I have heard of this working. The problem is that I don't think one ip range can fileshare talk etc with the other. Here is what I would personnally do is set up a load balancing server that recieves both connections and spreads out the bandwidth as needed. I'm sure this is possible in linux with a bit of work or you could just purchase a server that does that for you. I've seen servers that do this with 6 T1 lines. I know it is possible. As for the two IP addresses on the same network card. The only way I've seen that work is with vmware.
July 25, 2007 9:06:40 PM

Actually I set this up on a test network using 2 actual ISP's and it worked just fine. I just pointed one address at one IP on one pc with the server having both and I could talk to the server and surf. I let it run for a couple days w/o any problems. But tommorow we go live with a bunch of pc's and I guess that will be the telling tale.

I am aware of using two NIC's and setting up routing services ect but my opinion there is so little use made of a gigabit connection on an internet connection I thought this would be fun to try
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July 27, 2007 2:12:18 PM

Good glad you proved me wrong. Learn something everyday. So let me get this straight you had two network gateways on the same network and would just pick which computer went to which gateway. I'm trying to figure out where the two ips on the same network card came into play.
Anonymous
July 27, 2007 9:39:25 PM

I'm still trying to figure out how 2 ips can be assigned to the same NIC.

Grumpy
July 31, 2007 1:38:10 AM

Some network cards can have multiple IP addresses.

I think this is when a single NIC is a member of more than 1 VLAN. The NIC would have 2 or more IPaddresses, but each IP address would be a member of a seperate VLAN. To do this you need a card that supports VLAN tagging. I know that the Intel Gigabit Pro GT PCI cards will do this. I think that most of the other Intel gigabit network chipsets support this as well. As far as I know they will do this on a normal 10/100BT connection.

The problem would be getting a switch that supports multiple VLANs on one port. You would need to check that switch and the NIC used support this. If you need commications across the 2 or more VLANS then you will need a router or a Layer 3 switch. Standard Layer 2 switches may support VLANs, but will not switch traffic between those VLANs.

The VALN tagging addes a few extra bytes to the Ethernet frame, and this does mean that many ethernet adapters will not read tagged frames. This would mean that the VLANs with the tagged frames would have to be kept to VLANs with ethernet adapters that support tagged frames. This rules out ~90% of existing 10/100 ethernet adapters.

Rob.

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