All language subtitles for 5. Speed & Duplex Demo Fix Other Switch Issues

So we now need to fix this link between 2950-1 and 2950-2

both switches are showing messages that there's a duplex problem.

So CDP does a nice job here of showing us that there's a problem rather sh run int f0/4

We can see the speed and duplex are hard coded.

Sh run int f0/4 on this side it's 100 half duplex, on this side it's 100 full duplex.

So that’s a simple fix of setting a duplex to full.

the interface has gone down and comes up again and hopefully that’s resolve the problem

we could clear the counters as n example on F0/4 and do the same here

clear counters f0/4 and then we could after while look at those counters
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and see if we find any problems
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but that should have solve the problem of a duplex mismatch.
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To confirm it sh int f0/4 rather the tap here we can see, so here’s the command
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here’s the speed and duplex of the interface. Interface is up, up and it’s connected.
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sh int f0/4 on switch 2. Here’s the command once again.
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Duplex and speed are shown here as well.
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Interface is up, up and it’s connected.
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We’re not seeing any errors on this interface
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and on this one, we are also not seeing any errors.
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So that hopefully has resolve the problem on this link and this link.
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So be careful hard codings speed and duplex.
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Auto negotiation may negotiate correctly but it may not, generally today with gigabit
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and faster links your problem are not as bad as they used to be on 10100 links.
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Let see what happens if we configure speed and duplex on one side
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and leave the other side for autonegotiation.
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So on 2950-1 we will configure this interface with the speed of 100
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duplex of full interface is gone down, interface will hopefully come up and there you go.
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Here is the 3750 and we can see that’s it's complaining about a duplex mismatch.
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So sh run int f0 f1/0/3 no duplex or speed is being configured on this interface.
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sh int f1/0/3 this side is using 100 Meg half duplex
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where's this side is using 100 meg full duplex.
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So if you have 1 side configured for autonegotiation and the other side is hard-coded
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you may have a problem because this side is not negotiating
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with the other side and this side may take a full back decision.
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sometimes it’s able especially on gigabit and later interfaces to still work out
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what the other side is using and set its duplex and speed accordingly
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but here it wasn’t able to do that because the 2950's are older switches.
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So to resolve this, let's configured the 2950 for autonegotiation.
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So F0/1 this interface speed, auto, duplex, auto interface has gone down
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hopefully it will come up and hopefully they'll be able to negotiate successfully.
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S0 3750 showing up, 2950 showing up sh int f1/0/3
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Full duplex 100 meg, so that side is 100 meg full duplex.
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do sh int f0/1 on this side full duplex 100 meg.
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So they’ve negotiated successfully.
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so moral of the story is either configure both sides for autonegotiation or hard code
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both sides, generally today you’re going to allow both sides to auto negotiate.
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sh run int f1/0/1 sh run int f1/0/1
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now this is the link between the 2 3750's
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f1/0/1 this interface isn’t currently connected, so we’ve got 1 interface F1/0/1
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between the 2 3750's 1 side is not set for speed and duplex it's set for auto.
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The other side is using 100 half but in this case
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The side set for auto negotiation has reverted to 100 meg half duplex.
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So that’s work out ok, in this example, however if I change this to have a duplex of full
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the negotiation will probably fail and will have a duplex mismatch.
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Interfaces have come up, let’s see what its done.
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In this example it’s negotiated correctly full duplex 100 meg.
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This side do sh int f1/0/1 full duplex 100 meg
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So we manually configured this side with speed and duplex
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this side has been able to work out what the speed and duplex should be.
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So let’s set the speed here to 10 and the duplex to half.
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And let's see if the switches can successfully negotiate that.
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So interfaces is come up, sh int f1/0/1 and I'll simply include the duplex
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so we don’t see all the output, notice here its negotiated properly.
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So on this switch, it’s been manually configured for half duplex 10 meg
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and this switch has successfully negotiated that if I change the duplex here to full
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let's see what happens now when the interface comes up
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so here it's 10 meg full duplex, on this side it's also 10 meg full duplex.
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So the 3750 is on negotiating correctly without any problems
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but that wasn’t happening between a 3750 and the 2950.
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So let’s set the speed to 100.
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So sh int and look at the duplex that’s been set
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try that again 100 full duplex, this side 100 full duplex.
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So in this case when I set the 1 side it’s successfully negotiating with the other side
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but we have problems with negotiation between 3750 and 2950.
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So generally the moral of stories is, autonegotiation on both sides
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or hard code on both sides, mixing and matching can cause problems.
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Today the general recommendation is use auto everywhere except perhaps between core links
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where you wanna hard-code both sides to increase the speeds of that interface coming up.