#CCENT and #CCNA Fast Start: a ROAS Question

certskills
By certskills May 10, 2013 09:05

The new #CCENT and #CCNA exam topics state that we need to be ready to configure and verify Router on a Stick (ROAS), including encapsulation and subinterfaces. Today’s post poses a question that requires those skills. This post asks the question, with the next post listing the answer. Enjoy!

The Question

(Wendell’s note to self: internal question number 111.)

Router B1 can correctly route IPv4 packets between the two LAN subnets shown in the figure. The router can also route packets to/from other subnets to the left of router B1 (not shown in the figure). R1 uses ROAS. Switch SW1 uses VTP Transparent mode, 802.1Q trunking on the link connected to router B1, and the default native VLAN.

Consider the configuration options. Which of the following answers must be true about the configuration on B1 and SW1?

A) B1 must have an interface gigabitethernet 0/0.10 command, with a subcommand that adds an IPv4 address from subnet 10.1.10.0/24

B) SW1 must have an interface command creating a subinterface of Gigabit 0/1, with that subinterface having an encapsulation dot1q 20 interface subcommand

C) B1 must have an encapsulation dot1q command inside the configuration section for the physical interface (under the interface gigabitethernet 0/0 command)

D) B1 must have an interface command creating a subinterface of Gigabit 0/0, with that subinterface having an encapsulation dot1q 20 interface subcommand

E) SW1 can use either the switchport mode dynamic desirable or switchport mode dynamic auto subcommands on interface G0/1

(Note that unlike the real Cisco exams, this sample question does NOT identify the number of correct answers, just to add to the challenge level.)

Figure 1: ROAS: One Router LAN Interface, >1 VLAN and Subnet

Answers next post. Enjoy!

Related Posts

Introduction to this topic as it exists in the new CCENT and CCNA exams:

More Practice Questions:

This question is like those you get if when you buy the ICND1 100-101 Official Cert Guide. This blog also lists various practice questions as well. For more questions on a large variety of topics:

#CCENT and #CCNA Fast Start: Router on a Stick (ROAS) Overview
Answer to the ROAS Question
certskills
By certskills May 10, 2013 09:05
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3 Comments

  1. Bav August 7, 09:46

    Hi Wendell,

    Can’t seem to find the next post containing the answer. If there isn’t one can you share the answer here please?

    A) No. If it wasn’t for the word “must” I think this could have been a valid answer. In the cert guide it says the subinterface number does not need to be the same as the vlan ID as per the encapsulation command.

    B) No. Sub interface(s) are created on the router only. On the switch you only need to configure the VLANS and set the trunking mode to trunk.

    C) No. If configuring to put the Native VLAN on the physical interface then you only need to set the IP address.

    D) Yes..sort of. We do need at least 1 subinterface and this could hold the encapsulation dot1q 20 command. But the wording threw me off a bit. “creating a subinterface of Gigabit 0/0”. Gi 0/0 isn’t a subinterface, or did you mean to say create a subinterface under Gi0/0? e.g. Gi0/0.20.

    E) No. Trunking needs to be set statically on both ends of the link.

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