All language subtitles for 3. Speed & Duplex Demo Late Collisions

Here’s router 1, which is this device

and I'll ping router 2 from router 1 to see if ping succeed.

So ping 10.1.1.2 ping succeed.

But notice we are getting a message that there's a duplex mismatch

between the router and the 2950-1 switch.

So we’ve been told that there’s a duplex problem here and on the switch

we're seeing that there’s a duplex mismatch on F0/3 to the router.

So we’ve been told that there’s a duplex problem here

but we're also told that there’s a duplex issue on F0/4 to the 2950-2 switch on F0/4
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so there’s a problem here as well.
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Now you may not be physically connected to the console
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and hence you may not see this issues
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that’s a good reason to use a syslog server or a management application
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from a company such as SolarWinds.
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So let’s ping router 2 again.
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Ping succeeds, so pings aren't necessarily a good way to test for duplex mismatches.
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However I'll do an extended ping to that router so let’s try that again 10.1.1.2
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I'll send a thousand pings and I’m gonna make the datagram size, a large size
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so we wanna send a large of traffic unto the network and hopefully we'll encounter
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problem and there you go, we’ve got a message saying a late collision has occurred.
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So this is a problem you my encounter.
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One side may tell you that there are late collisions as you can see over there.
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Were getting a number of late collisions, on the other side were not seeing that.
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so on the switch sh int f0/3 we're not seeing a lot of late collisions
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the configuration of that interface is set to a speed of 10 meg
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and duplex are full but notice on this side sh running-config int f0
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this side has its speed sets to 100 lets confirm that.
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sh int f0 notice the duplex is half, speed is set in this example to 10 Mbps
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so the router because it can't negotiate properly with the other device in this case
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the 2950 switch has set its speed to a value of 10 meg half duplex.
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So the point to remember is when there is a mismatch
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the side that is set for half duplex will see a late collisions on the connection
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but this only occurs when you're sending enough traffic.
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so a standard ping doesn’t show that problem
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but when a large amount of traffic is sent on this half duplex connection
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we're getting a late collisions on the switch side sh int f0/3
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notice the speed is full duplex 10 Mbps where's in the router it's half duplex 10 Mbps.
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even though I configured it to use 100 Mbps, its using a failed back position
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of the worst case scenario which is 10 meg half duplex
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and in this case we're having that problem.
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Notice this is 100 bases TXFX where's this side is 100base TX.
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So in this example the router has gone for half duplex 10 Mbps
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where's the switch is is using 10 meg full duplex
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and hence we’ve got a duplex mismatch.
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So in summary we get told by CDP that there is a duplex mismatch.
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The local interface is not using full duplex
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where’s the other side is using full duplex.
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Pinging a device doesn’t tell us that there’s a problem
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but when large packets are sent
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It uses main counter drops for throughput and you may see late collisions.
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So let me exaggerate that link again, send a thousand pings
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large data gram size, sh int f0/3
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Notice we are now seeing the late collisions taking place on the interface.
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So on a half duplex side, we see this output of late collisions.
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On the interface, sh int f0 notice the number of late collisions has increased.
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On the full duplex side we make it input errors such as CRC errors or runt frames.
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so in this example we’ve got 28 input errors, 15 CRC's
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were aren’t seeing any runts but we are receiving duplex mismatch messages.