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how to identify bad nic
- Thread starter dogsbod
- Start date
Narrow your problem. Is a specific server or workstation slow? Do the connectivity problems occur at a specific time of day or at specific intervals?
Bad nic's generate bad packets. A computer with a bad nic should be slow on the network. Periodically I find a workstation NOT with a bad nic but one hard configured for "full duplex" where the switch port is set to auto negotiate. In this case, I see errors on the switch port. Check your switch port error conters. Clear them and see if errors return. If you have hubs, plug in your network analyser and see what happens.
Are there multiple/unused protocols which generate excessive broadcasts (netbeui, ipx, dlc)? Configure your printers for only one protocol. Remove unused protocols from your workstations and servers.
Bad nic's generate bad packets. A computer with a bad nic should be slow on the network. Periodically I find a workstation NOT with a bad nic but one hard configured for "full duplex" where the switch port is set to auto negotiate. In this case, I see errors on the switch port. Check your switch port error conters. Clear them and see if errors return. If you have hubs, plug in your network analyser and see what happens.
Are there multiple/unused protocols which generate excessive broadcasts (netbeui, ipx, dlc)? Configure your printers for only one protocol. Remove unused protocols from your workstations and servers.
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- #3
thanks for the reply. Only tcp\ip runs on network, or so I thought, I did a ethereal scan and saw printers broadcast ipx packets, so disabled that. I will check the switch for errors as suggested. If I placed a server on a hub and a pc with say ethereal on the same hub and then switch( used by lan) on 3rd port of hub monitoring all traffic between servers and rest of the network, will this cause a performace decrease, also is this the correct way to monitor traffic between the a server and rest of lan.
Dogsbod asked: "If I placed a server on a hub and a pc with say ethereal on the same hub and then switch( used by lan) on 3rd port of hub monitoring all traffic between servers and rest of the network, will this cause a performace decrease, also is this the correct way to monitor traffic between the a server and rest of lan."
If the connection between the server(s) and the switch was 100Mbs full you'll now have to set it at 100Mbs half duplex when the hub is used because a true hub is a shared media device and can not support full duplex. Wityh just those two devices conencted you shouldn't see much of a performance hit, especially if most of the traffic is going out from the server to users rather than there being lots of traffic on both Rx and Tx.
Adding a PC to the hub with Ethereal or a similar program should not impact it in any noticeable way because the NIC of the PC should be set up as a monitor card in promiscuous mode meaning "listen only". If you need to monitor this connection in full duplex mode a 10/100 copper tap is required. This will have no impact and allow the connection to stay at 100Mbs full but a PC with Ethereal will only be able to listen to either Rx or Tx one at a time because the duplex tap hands off separate copies of Rx and Tx. These taps have a street price of ballpark $400- $500 (I think). Another option is an "aggregation tap" which combines the Rx and Tx copies and allows a PC with Ethereal to listen to both sides of the full duplex conversation in a single stream of data. But these are more expensive - ballpark $800 - $900 and probably overkill for your project.
If you go ewith the hub solution be sure to look for the little Netgear model that is TRUE hub. MOst so-called small hubs are actually unmanaged switches and your PC with Ethereal will hear only braodcast traffic when it's attached.
Owen O'Neill
Datacom Systems Inc.
Northeastern SE
If the connection between the server(s) and the switch was 100Mbs full you'll now have to set it at 100Mbs half duplex when the hub is used because a true hub is a shared media device and can not support full duplex. Wityh just those two devices conencted you shouldn't see much of a performance hit, especially if most of the traffic is going out from the server to users rather than there being lots of traffic on both Rx and Tx.
Adding a PC to the hub with Ethereal or a similar program should not impact it in any noticeable way because the NIC of the PC should be set up as a monitor card in promiscuous mode meaning "listen only". If you need to monitor this connection in full duplex mode a 10/100 copper tap is required. This will have no impact and allow the connection to stay at 100Mbs full but a PC with Ethereal will only be able to listen to either Rx or Tx one at a time because the duplex tap hands off separate copies of Rx and Tx. These taps have a street price of ballpark $400- $500 (I think). Another option is an "aggregation tap" which combines the Rx and Tx copies and allows a PC with Ethereal to listen to both sides of the full duplex conversation in a single stream of data. But these are more expensive - ballpark $800 - $900 and probably overkill for your project.
If you go ewith the hub solution be sure to look for the little Netgear model that is TRUE hub. MOst so-called small hubs are actually unmanaged switches and your PC with Ethereal will hear only braodcast traffic when it's attached.
Owen O'Neill
Datacom Systems Inc.
Northeastern SE
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