duplex/speed setting

[mumetsu]

Regarding a setting on Catalyst and PC's NIC(10/100),which selection is the best way ?

I understand it like below. Is it correct ?

1)NIC:100/full,Catalyst:100/full

2)NIC:auto,Catalyst:100/full

3)NIC:100/full,Catalyst:auto

4)NIC:auto,Catalyst:auto

[raju]

It is recommended to leave auto mode on both sides (Switch side & NIC ) . I know some of the application vendors like SAP recommends to force on both the sides ( NIC card and Switch port) to 100/full . In our case, SAP servers are running on Windows Platform.

Thanks

Raju

[Kevin Dorrell]

I would recommend 4, auto-auto; the NIC and the catalyst will negotiate, and will usually settle on 100-full. Option 1 is also OK, because the setting are the same at both ends.

Options 2 and 3 will give you big problems. For the reason, let us look first at option 3. You have forced 100-full on the NIC, and left the Catalyst in auto. The NIC is fixed 100-full, and so will not negotiate. The Catalyst will expect negotiation so it has to guess. It can work out the 100 from the clock it sees, but it cannot possibly guess the duplex. So it reverts to the default, which is half-duplex. So ... a duplex mismatch. The same is true of option 2, but the other way round.

Ironically, if you follow the argument above, you will see that 100-half will interwork correctly with auto. But I would reccommend, auto-auto. It is the default, and the one that almost always works correctly.

Hope this clarifies things.

Kevin Dorrell

Luxembourg

[mohamed-khadr]

From my own experience with big server farms, a better and safe config is : 100/full on both ends. That way u eliminate any chance for dup mismatch, not to mention faster access (200 m/s) on bot directions.

[Kevin Dorrell]

It is true that the port will come up faster, and you know exactly where you stand. But on the other hand, the administrative overhead will be greater, and I have almost always found that auto-auto works well. It only doesn't work well when the server people decide to set 100-full without telling me.

It's horses-for-courses really.

Kevin Dorrell

Luxembourg