what will happen if I put another network card in my PC?

Hi all

I'm connected to the LAN, what will happen if I put another network card in my desktop and connect it to the same hub that is connected to the wall accessing the LAN. (so theres two cards in same PC on the LAN)

Will there be an IP conflict?
Will bandwidth increase?
Is there anything that can be doen with two cards?
Is this a stupid and pointless thing to do?

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depends - probably

You can do all sort of things with two network cards in one box.  You can setup the machine as a proxy server, router, gateway, etc.  The only way you would have an ip conflict would be if you set up the ip addresses on the machine to be static and gave both cards the same ip address.  When you install a new card it will show up in your network properties and you will have to set the settings for tcp for it as well.  You shouldn't have a conflict.
It's only pointless if you don't plan on using the card.  The extra card could be used for nothing more than a redundant connection to the network.
Pete LongTechnical ConsultantCommented:
>>You can setup the machine as a proxy server, router, gateway
I dont think that is the poster intention, i think they need to replace their possible 10 mbps hub with a 10/100 switch or put the spare network card they have come across in the top drawer as a spare.


good answer :0)

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>>>Will there be an IP conflict?

Not necessarily. Only if they get configured with the same IP addresses.

>>>Will bandwidth increase?

Possibly,  only by the use of adapter teaming.

>>>Is there anything that can be doen with two cards?

As said above you have the routing/firewalling options PLUS setting up an adapter team if your switch supports it. This will increase the bandwith of your system by using both cards bandwith together, but has to e configured correctly and has to be connected to a switch which supports this feature.

>>>Is this a stupid and pointless thing to do?

If your not looking at any of the above solutions, then maybe. Stupid? At worst, you're going to loose connectivity which will be obvious immediately. This can be rectified by disabling the new card. Pointless? You may want the card there as a spare incase the first one fails. This can be brought online if the otherone fails very quickly. This is certainly not a pointless exercise.
>Will there be an IP conflict?

Only if you configure it so.

>Will bandwidth increase?

Only under very specidfic conditions for which you would have to configure.

>Is there anything that can be doen [sic] with two cards?

Well, you could run two networks on the same wire (not generally advisable) - the second card could be used for inclusion in a maintenance network.  The failover option has been mentioned already.  Also, you could use it to increase bandwidth if the first card is known to be a bottleneck and you have special software configured and running (also already mentioned).

>Is this a stupid and pointless thing to do?

Without a specific goal?  Probably.


>Will there be an IP conflict?
DHCP assigns addresses based on the MAC address of a card, so you wouldn't have a conflict unless your explicitly set the addresses the same. Some sites with tight security administer their DCHP servers so that unauthorized machines can't get an address. Guessing an address in a DHCP environment is a good way to create a conflict.

>Will bandwidth increase?
There are schemes to 'team' or 'load balance' two (or more) cards. This can be an operating system feature or a feature of the card's drivers. Some require a special configuation on the switch they're connected to, such as Fast Ether Channel.
The device you're connected to would have to have bandwidth available, if you're on a hub with a 10Mbit uplink, there's no additional bandwidth to take advantage of. If you're on a switch, there would have to be something upstream with more bandwidth than one of your cards to do you any good.

>Is there anything that can be doen with two cards?
Two cards can also be put into 'failover' mode, wherein you use one card normally, but if there is a fault, the other card will take over. Two cards can also be used to route traffic between them. Internet Connection Sharing is one example of this configuration. Using a machine as a general router, proxy or firewall are others.

>Is this a stupid and pointless thing to do?
It depends on your motive. If you're in a corporate environment I'd suggest against it as somebody will come knocking.
If you're at home, it might be educational.

Huseyin1Author Commented:

Thanks for all your comments.

I was just thinking on the theory of increasing bandwidth, thats my gole, I was thinking connecting both NIC to the SAME network to do this, I dont want a spear card just sitting in my PC, im the tech guy here in the building, and we have about 100 NIC spear in the store/test room.

so, I have to allocate 2 different IP addresses to access the same network and whats adapter teaming?

thanks again all.

Adapter teaming enable you to combine the 2 ethernet connections into 1 etherchannel. This will enable you to increase your bandwith. the other option with teaming is for fault tolerance which doesn't sound like your goal.

Preferably, you need adapters of the same make, but this isn't a prerequisite.
>I was just thinking on the theory of increasing bandwidth, thats my gole
What kind of switch are you connecting to?
What kind of cards?

Huseyin1Author Commented:
the cards are 3Com EtherLink III ISA (3C509b-TPO) in PnP mode,
Switch, erm,,,,,, we have routers and hubs in the basement , sorry. I'd like to read up on adapter teaming, any links?
Ooops. I don't think these cards will support it.
I haven't seen one of these for years. I thought people had stopped using them.
Anyway, for some info on adapter teaming try
http://www.intel.com/support/network/adapter/ans/teaming.htm for intel specific information.

I can't find anything on 3com yet, but will post it when I can. ;-)

http://support.microsoft.com/default.aspx?scid=http://support.microsoft.com:80/support/kb/articles/q254/1/01.ASP&NoWebContent=1 for Microsofts OS information.

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From what I can tell, 3COM don't produce an adapter teaming solution except for the 3C996 gigabit ethernet card which is based on the broadcom chipset. As broadcom supported this feature on this NIC, then this card will support it.
There is information in the documentation on how to configure teaming.

see http://www.networkcomputing.com/914/914r2side1.html

for a theoretical discussion, but

You have 10Mb cards.
You're connected to a hub.
Unless the hub has a 100Mb uplink, the total bandwidth on the hub equals the bandwidth of one of your cards, so you're not going to see any benefit.

You have to look at the whole upstream network.
If you could get each NIC on a seperate hub that was fed by different switch ports you might see some gains, but you can't aggregate the bandwidth on those cards on hubs, any one connection will use only one card, so you'll never see more than 10Mbps on any sessions anyway.

Huseyin1Author Commented:
thanksm all

good link

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