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New Member

Ethernet speed and duplex status

Situation from the real exam: fa 0/0 is up/down. In show int fa 0/0 BW is 10000Kbps (i.e 10 Mbps), but as you know this only a description parameter. Another funny thing: encapsulation HDLC. Is it possible for Ethernet interface?

When I configured fa 0/0 with command speed 100 it became up/up. But it was just ‘try this, try that’ method.

Is it any way to check fa 0/0 speed and duplex?

Thanks

6 REPLIES
VIP Purple

Re: Ethernet speed and duplex status

Hello,

to be honest I have never seen a (Fast)Ethernet interface with HDLC encapsulation, can you post the output of the show interface fastethernet0/0 command ?

The best way to check the duplex/speed settings to which your FastEthernet needs to be set to is to configure the interface with the settings duplex auto and speed auto. This way, it negotiates the settings depending on what the other side is configured to. If you hardcode your interface to 10MB half duplex and the other side is configured for 100 full duplex, the link does not come up. If you have your interface configured for the auto settings, it will adapt according to the settings of the other side.

HTH,

Georg

New Member

Re: Ethernet speed and duplex status

Hi Georg,

I can't post show command output because it was from a ccnp exam simulator question. Your advice is good, but in my question I asked how I could check speed/duplex, not how to configure ethernet interface.. As you might know in exam situation there is not enough time to play with all possible tricks to solve the problem. But the faster you can pinpoint the cause of problem, the better you off.

New Member

Re: Ethernet speed and duplex status

The output of the "sh inter f0/0" should tell you what is the current speed and duplex. Here's an example output of the command:

FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0003.6b31.3160 (bia 0003.6b31.3160)

Description: connected to LAN

Internet address is 192.168.100.254/24

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliability 254/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Half-duplex, 10Mb/s, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

---snipped---

Notice line 9, it states the current duplex and speed settings, respectively, whether they were detected automatically or configured manually. The same line also identifies what type of interface it is (100BaseTX/FX).

The HDLC encapsulation you saw on the exam was probably a simulator flaw. As always, no simulator can beat the real thing.

New Member

Re: Ethernet speed and duplex status

OJ88!

The matter of fact is that for some reason in the show int e0 command on my home lab 2503 router with IOS 12.2 I don’t have neither speed information, nor duplex status.(see below) I thought this is the normal command output. I think the possible reason for such unusual output may be just the fact, that this card supports only 10 Mbit and half-duplex. Do you have any other explanations or comments. Thanks.

Joseph

Lower#sh int e0

Ethernet0 is up, line protocol is up

Hardware is Lance, address is 0000.0c35.0de7 (bia 0000.0c35.0de7)

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliability 128/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output 00:00:40, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 input packets with dribble condition detected

175 packets output, 39024 bytes, 0 underruns

175 output errors, 0 collisions, 15 interface resets

0 babbles, 0 late collision, 0 deferred

175 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

New Member

Re: Ethernet speed and duplex status

That is correct. My first reply was based on your original query, where a fastethernet (fa0/0) was used. You are correct that there's no point in showing the connection speed and duplex when the router can only support 10Mb/s and h-duplex, such as from a 2500 series router.

New Member

Re: Ethernet speed and duplex status

OJ,

Is it always the case with fa interface that speed and duplex status will be shown at sh int fa command? Or only if card supports dual speeds (10/100) and half/full duplex?

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