Section 1 – Implement VLAN based solution, given a network design and a set of requirements
QUESTION NO: 16
Two Company switches are connected via a trunk link. In this network, the original frame is encapsulated and an additional header is added before the frame is carried over a trunk link. At the receiving end, the header is removed and the frame is forwarded to the assigned VLAN. This describes which technology?
A. DISL
B. ISL
C. DTP
D. IEEE 802.1Q
E. MPLS
F. None of the other alternatives apply
Answer: B
Explanation:
Inter-Switch Link Protocol
The Inter-Switch Link (ISL) protocol is a Cisco proprietary method for preserving the source VLAN identification of frames passing over a trunk link. ISL performs frame identification in Layer 2 by encapsulating each frame between a header and trailer. Any Cisco switch or router device configured for ISL can process and understand the ISL VLAN information. ISL is primarily used for Ethernet media, although Cisco has included provisions to carry Token Ring, FDDI, and ATM frames over Ethernet ISL. (A Frame-Type field in the ISL header indicates the source frame type.)
When a frame is destined out a trunk link to another switch or router, ISL adds a 26-byte header and a 4-byte trailer to the frame. The source VLAN is identified with a 10-bit VLAN ID field in the header. The trailer contains a cyclic redundancy check (CRC) value to ensure the data integrity of the new encapsulated frame. Figure 6-3 shows how Ethernet frames are encapsulated and forwarded out a trunk link. Because tagging information is added at the beginning and end of each frame, ISL is sometimes referred to as double tagging .
QUESTION NO: 17
Refer to the exhibit. The switchport output in Figure 1 displays the default settings of interface FastEthernet 0/13 on switch SW1. Figure 2 displays the desired interface settings. Which command sequence would configure interface FastEthernet 0/13 as displayed in Figure 2?
A.SW1(config-if)# switchport trunk encapsulation dot1q
SW1(config-if)# switchport mode trunk
SW1(config-if)# switchport trunk native DATA
SW1(config-if)# switchport trunk allowed vlan1,10,20
B.SW1(config-if)# switchport trunk encapsulation dot1q
SW1(config-if)# switchport mode dynamic auto
SW1(config-if)# switchport trunk native DATA
SW1(config-if)# witchport trunk allowed vlan add 1,10,20
C.SW1(config-if)# switchport trunk encapsulation dot1q
SW1(config-if)# switchport mode dynamic desirable
SW1(config-if)# switchport trunk native vlan DATA
SW1(config-if)# switchport trunk allowed vlan 1,10,20
D.SW1(config-if)# switchport trunk encapsulation dot1q
SW1(config-if)# switchport mode dynamic desirable
SW1(config-if)# switchport trunk native vlan 10
SW1(config-if)# switchport trunk allowed vlan 1,10,20
E.SW1(config-if)# switchport trunk encapsulation dot1q
SW1(config-if)# switchport mode dynamic desirable
SW1(config-if)# switchport trunk native vlan 10
Answer: D
Explanation:
According to the exhibit, the Operational Mode is down meaning that the port has been administratively shut down. To work properly the Operational Mode should be in up. So use no shutdown command to bring interface fastethernet 0/1 will fix this issue.
QUESTION NO: 18
You are the network administrator at Company and switch R1 is configured as shown below:
Interface gigethernet 0/1
Switchport mode trunk
Switchport trunk encapsulation dot1q
Switchport trunk native vlan 5
If untagged frames are arriving on interface gigethernet 0/1 of R1, which of the following statement are correct?
A. Untagged frames are automatically assumed to be in VLAN 5.
B. Untagged frames are defaulted to VLAN 1 traffic.
C. Untagged frames are dropped because all packets are tagged when dot1q trunked.
D. Untagged frames are determined on the other switch
E. Untagged frames are not supported on 802.1Q trunks.
Answer: A
Explanation:
Each physical port has a parameter called PVID. Every 802.1Q port is assigned a PVID value that is of its native VLAN ID (default is VLAN 1). All untagged frames are assigned to the LAN specified in the PVID parameter. When a tagged frame is received by a port, the tag is respected. If the frame is untagged, the value contained in the PVID is considered as a tag. All untagged frames will be assigned to the native VLAN. The native VLAN is 1 by default, but in this case the native VLAN is configured as VLAN 5 so choice A is correct.
QUESTION NO: 19
Refer to the show spanning-tree mst configuration output shown in the exhibit. What should be changed in the configuration of the switch SW_2 in order for it to participate in the same MST region?
A. Switch SW_2 must be configured with an instance number of 2.
B. Switch SW_2 must be configured with a different VLAN range.
C. Switch SW_2 must be configured with the revision number of 1.
D. Switch SW_2 must be configured with a different MST name.
Answer: C
Explanation:
MST is built on the concept of mapping one or more VLANs to a single STP instance. Multiple instances of STP can be used (hence the name MST), with each instance supporting a different group of VLANs.
In most networks, a single MST region is sufficient, although you can configure more than one region . Within the region, all switches must run the instance of MST that is defined by the following attributes :
MST configuration name (32 characters)
MST configuration revision number (0 to 65535)
MST instance-to-VLAN mapping table (4096 entries)
Example of configuration of MST
Switch( config)# spanning-tree mode mst
Switch( config)# spanning-tree mst configuration
Switch( config-mst)# name name
Switch( config-mst)# revision version
The configuration revision number gives you a means to track changes to the
MST region configuration. Each time you make changes to the configuration, you should increase the number by one. Remember that the region configuration ( including the revision number) must match on all switches in the region . Therefore, you also need to update the revision numbers on the other switches to match.
Switch( config-mst)# instance instance-id vlan vlan-list
The instance-id (0 to 15) carries topology information for the VLANs listed in vlan-list. The list can contain one or more VLANs separated by commas.
You can also add a range of VLANs to the list by separating numbers with a hyphen . VLAN numbers can range from 1 to 4094. (Remember that by default , all VLANs are mapped to instance 0, the IST.)
Switch( config-mst)# show pending region configuration:
Switch( config-mst)# exit
So belong the routers in same MST region, MST attributes should be same, in Company2 router revision number is not same so to make belong the Company2 router on same MST region, revision number should be 1.
QUESTION NO: 20
Which of the following statements is true about the 80/20 rule (Select all that apply)?
A. 20 percent of the traffic on a network segment should be local
B. no more than 20 percent of the network traffic should be able to move across a backbone.
C. no more than 80 percent of the network traffic should be able to move across a backbone.
D. 80 percent of the traffic on a network segment should be local
Answer: B,D
Explanation:
The 80/20 rule in network design originated from the idea that most of the traffic should remain local to the LAN, since bandwidth is plentiful compared to WAN links, and a great deal of broadcast traffic that is evident at the LAN is not passed over the backbone.
Note: With the availability of inexpensive bandwidth and centralized data centers, this rule appears to have become obsolete. In fact, most networks have taken on the 20/80 rules, as opposed to the legacy 80/20 rule.
