NIC conflict
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Thread: NIC conflict

  1. #1
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    NIC conflict

    Just wanted to know if 2 NIC's could "conflict" with each other.

    i am setting up a simple network (2pc's) and i figured a NIC is a NIC. i mean they both have RJ45
    ports so what could go wrong?

    anyway, could these NIC's just not like each other very much or should i be looking for another problem?

  2. #2
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    Drew, what do you mean? DO you have one box with 2 Nic's in it? Then make sure (if they are ISA) that they do not use the same resources (IRQ , I/O). Best way to resolve this is if they use jumpers, search the nic manual and set the jumpers correct. Or if it's without jumpers or soft-config, use the NIC config program in a dos environnement. Start with a bootable floppydisk with the prog on it. If the NIC's are PCI they are normally recognized by your motherboard and configured.

    Are you talking about different pc's connecting to each other? You wonder if nic's are nic's? You are talking about ethernet . Normally they can all talk with each other. The difference is the maximum speed they can communicate 10 / 100 or 1000 (gigabit).
    You say they both use RJ45. If it are older cards, or cards you got from some1 make sure you are not confusing a token ring card with a ethernet nic or with a ISDN modem. So, it's not cause it has a RJ45 port that it's a ethernet NIC.

    But if it are 10BaseT or 100BaseTX or Gigabit compliant Nic's, they normally 'talk' with each other. Make sure the nic can work with your OS's. If you still encounter probs, check the cabling.

  3. #3
    AO übergeek phishphreek's Avatar
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    VictorKaum: Very good answer.

    I just wanted to add one thing.
    Though the probablility of this happening is very low... it can still happen.

    If you have an older NIC and a new NIC made by the same manufactuerer, then there is a chance that they have the same MAC addresses.

    What happeded was, manufactureres ran out of MACs to assign to NICs so they just started reusing them.

    To fix that problem, if it ever occurs, visit the manufacturers' web site and under support/downloads you should be able to find a utility to change the MAC to your NIC.

    Or simply install a new NIC. They are a dime a dozen these days and the time it would take to reconfigure an old NIC you could have already installed a new one.

    Like I said... the probablility of this happening is slim to none, but I just wanted to add that.
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    "If you have an older NIC and a new NIC made by the same manufactuerer, then there is a chance that they have the same MAC addresses.

    What happeded was, manufactureres ran out of MACs to assign to NICs so they just started reusing them. "

    Woah, WOah reusing macs? I though that not suppose to happend, each NIC has its Own Unique ID, the Burned in Address in the card, that should never happen. on the top of that, if you do have 2 nics with the same mac, even if its in the same computer or the same LAN Topology then two of those computers cannt perform, thus being a MAC Conscrep. its just like having 2 computerswith the same IP...

    Anyhoo i got to 2 NICS in my PC just for the sake of being board, there both PCI, there is no HUGE ISSUE with doing that except if they share the same IRQ like VICTOR said.

    So yeah go for it, even though its stupid to do that, and you should just buy hub. it will save you alot of time, and in networking time is precious... use that extra NIC towards another PC.
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    thanx for the help guys.
    i am using 2pc's so it's one nic for each pc. what i ment in my post is that they are both ethernet nics. i played around and this is where i'm at...

    i know the nics + cable all "work" because i can ping 127.0.0.1 and...
    my xp machine SOMEHOW "found" the other pc. it's part of the network but not accessable for some reason. i KNOW that SOME information made it's way accross the wire as the name of the 2nd pc shows up on the first pc. i can't ping anything xcept loopback so this is strange.
    i don't know what's wrong exactly, i have the same network number but different host numbers [192.168.0.1] and [192.168.0.2] ... i also tried .4 and .8 though there was no difference.
    i am now thinking problem at the "upper layers" as cisco has helped me to test my network from the bottom up to find errors.

    btw ... bout the same MAC's we already went over that in class, although i've never come accorss that problem before, ill check just incase.

    any more thoughts?

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    Drew,
    What OS are you running on the other machine? I know that to access an XP share from a non-XP machine, the guest account has to be activated. I am assuming this is also true from an XP machine to an XP machine. Give that a try, if you can see the PC in network neighbourhood but cannot access it.
    Good luck!
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  7. #7
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    if you are running XP one thing you have to do is turn off the "firewall" that XP uses by default or you won't be able to browse it or ping it. The XP box can see other OS's and share on other machines fine, but nothing will be able to see it or use stuff on that box.

    You can find that setting under the network properties file, I think it was under the advanced tab but since I don't have an XP machine here in front of me I can't be 100% certian.




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  8. #8
    AO übergeek phishphreek's Avatar
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    know the nics + cable all "work" because i can ping 127.0.0.1 and...
    my xp machine SOMEHOW "found" the other pc. it's part of the network but not accessable for some reason. i KNOW that SOME information made it's way accross the wire as the name of the 2nd pc shows up on the first pc. i can't ping anything xcept loopback so this is strange.
    i don't know what's wrong exactly, i have the same network number but different host numbers [192.168.0.1] and [192.168.0.2] ... i also tried .4 and .8 though there was no difference.
    i am now thinking problem at the "upper layers" as cisco has helped me to test my network from the bottom up to find errors.
    I know that you've probably already thought of this... but

    Are you using any personal firewall? I know that in order for me to talk back and forth on my home network, I had to include the ip scheme that was trusted.
    I'm using Norton Internet Security on the m$ box(s) and the built in firewall on linux and I have a firewall at my border too. (I guess overkill, but the border is more like a proxy/firewall/router)

    To test that, just disable your firewall temporarily. If you can ping after that, then you know the problem is in your firewall.
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    no firewall so i'm still stumped ... i'll figure it wou somewhow, i'll try diff nics and diff cable and start from scratch.

    thanxs for all ur advice guys.

  10. #10
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    Drew, this may sound funny and is very basic, but in order to have a M$ workgroup network running make sure you have common network protocols, a common workgroup and common user names and passwords.

    TCP/IP is the default protocol for Windows 2000 pro and later, but windows 95 and 98 installed Netbeui and IPX/SPX compatible transport (NwLink) protocols as default. Therefor make sure you use the same protocols. You can not browse another box (browse the network) without a common protocol. Also user accounts must be the same. Therefor on your NT or XP pro box you need to create accounts that match the accounts on the other (Win9x) boxes. If the user can not be found in the SAM database, normal (browse) connection will not be allowed.

    So you need to set the correct network accounts, workgroup, passwords and protocols on your boxes, in order to have access to shares on NT based boxes.
    How-to? see: http://www.microsoft.com/support/kb/.../q258/7/17.asp

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