Switch question

This question comes from Odom’s CCENT/CCNA ICND1…..chap10 ethernet switch troubleshooting….. pg 269…..question #6 for those that have the study guide.

Switch SW1, a Cisco 2960 switch, has all default settings on interface Fa0/1, the speed 100 command configured on Fa0/2, and both the speed 100 and duplex half commands on Fa0/3. Each interface is cabled to a 10/100 port on different Cisco 2960 switches, with those switches using all default settings. Which of the following is true about the interfaces on the other 2960 switches?

a. The interface connected to SW1’s Fa0/1 runs at 100 Mbps and full duplex.
b. The interface connected to SW1’s Fa0/2 runs at 100 Mbps and full duplex.
c. The interface connected to SW1’s Fa0/3 runs at 100 Mbps and full duplex.
d. The interface connected to SW1’s Fa0/3 runs at 100 Mbps and half duplex.
e. The interface connected to SW1’s Fa0/2 runs at 100 Mbps and half duplex.

I understand why d is part of the answer, but a and b has me puzzled. I’m starting to think maybe this is a typo. If anyone could shed some light as to why a and b are correct it’ll be greatly appreciated.

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Comments

wbosher

Someone might correct me here but I think this is why -

a. The interface connected to SW1’s Fa0/1 runs at 100 Mbps and full duplex.

With all default setting the interface will be set to "auto" for both speed and duplex. Being a fast ethernet port the speed will be 100. The duplex (on auto) setting will then default to full on a fast ethernet port unless told otherwise.

b. The interface connected to SW1’s Fa0/2 runs at 100 Mbps and full duplex.

The speed is set to 100 manually, so the duplex (still set to auto) will default to full as with question a above.

I think this is right.

Somnipotent

Let's break it down...

Switch SW1, a Cisco 2960 switch

-default settings on interface Fa0/1 (default is auto for everything so that would be 100/full given the other side (as stated, a 2960 with default settings, is a 10/100 port)

-the speed 100 command configured on Fa0/2, (hardcoded to speed 100, left auto [full] for the duplex)

- both the speed 100 and duplex half commands on Fa0/3. (hard coded to speed 100 and duplex half)

Each interface is cabled to a 10/100 port on different Cisco 2960 switches, with those switches using all default settings. Which of the following is true about the interfaces on the other 2960 switches?

a. The interface connected to SW1’s Fa0/1 runs at 100 Mbps and full duplex.
b. The interface connected to SW1’s Fa0/2 runs at 100 Mbps and full duplex.
c. The interface connected to SW1’s Fa0/3 runs at 100 Mbps and full duplex.
d. The interface connected to SW1’s Fa0/3 runs at 100 Mbps and half duplex.
e. The interface connected to SW1’s Fa0/2 runs at 100 Mbps and half duplex.

chmorin

wbosher wrote: »

Someone might correct me here but I think this is why -

a. The interface connected to SW1’s Fa0/1 runs at 100 Mbps and full duplex.

With all default setting the interface will be set to "auto" for both speed and duplex. Being a fast ethernet port the speed will be 100. The duplex (on auto) setting will then default to full on a fast ethernet port unless told otherwise.

b. The interface connected to SW1’s Fa0/2 runs at 100 Mbps and full duplex.

The speed is set to 100 manually, so the duplex (still set to auto) will default to full as with question a above.

I think this is right.

I'm with you here. The question seems accurate.

wave

Wow, this question just caught me out too. The key thing I learned was that it would take both the speed and duplex commands being configured before IEEE auto negotiation was disabled completely.

On p. 286 the Odom book says that "If the speed is somehow known to be 10 or 100 Mbps, default to use half duplex." I didn't select answer B. because of that rule. I was wrong because although the speed command was configured, the duplex setting wasn't. SO, in this case, auto-negotiation jumped in and sensed the duplex as full and therefore answer B. is a correct answer.

Thanks guys!