Question 1.
If a port on Switch A has been configured using the DISL setting "auto," what will the result be if the connected neighbor port on Switch B has been configured to use the DISL setting "desirable"?

a) Switch A - Non-trunking, Switch B - Non-trunking
b) Switch A - Trunking, Switch B - Non-trunking
c) Switch A - Non-trunking, Switch B - Trunking
d) Switch A - Trunking, Switch B - Trunking
e) None of the above. This is not a valid configuration.

Answer

Question 2.
In order to establish an Ethernet trunk between a Cisco Catalyst switch and a non-Cisco switch, which of the following DISL trunk modes could you set on the Cisco switch to establish a trunk link between the two switches?

a) Desirable
b) Auto
c) Nonegotiate
d) Off
e) DISL Trunking is a Cisco proprietary function. Trunking between Cisco and non-Cisco equipment cannot be done.

Answer

Question 3.
In a network environment consisting solely of Cisco Catalyst switches, which of the following protocols may be used to enable the transport of multiple VLANs over an Ethernet trunk?
(Choose 2)

a) VLAN Trunk Protocol
b) Inter-Switch Link
c) Dynamic Inter-Switch Link
d) IEEE 802.1Q
e) IEEE 802.1D Spanning Tree Protocol

Answer

Answers

Question 1.
If a port on Switch A has been configured using the DISL setting "auto," what will the result be if the connected neighbor port on Switch B has been configured to use the DISL setting "desirable"?

a) Switch A - Non-trunking, Switch B - Non-trunking
b) Switch A - Trunking, Switch B - Non-trunking
c) Switch A - Non-trunking, Switch B - Trunking
d) Switch A - Trunking, Switch B - Trunking
e) None of the above. This is not a valid configuration.

Answer
d) Switch A - Trunking, Switch B - Trunking

Explanation
The DISL setting "Auto" sets a port to trunk if the connected switch has initiated negotiation. In order for a port set to "Auto" to trunk, the connected neighbor port must be set to the "On" or "Desirable" state.

The DISL setting "Desirable" sets a port to trunk and attempts trunking negotiation of the neighboring port. In order for a port set to "Desirable" to trunk, the connected port must be set to the "On," "Desirable," or "Auto" state.

Since Switch A and Switch B are set to modes favorable to trunking with each other, each switch port will be set to trunk.
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Question 2.
In order to establish an Ethernet trunk between a Cisco Catalyst switch and a non-Cisco switch, which of the following DISL trunk modes could you set on the Cisco switch to establish a trunk link between the two switches?

a) Desirable
b) Auto
c) Nonegotiate
d) Off
e) DISL Trunking is a Cisco proprietary function. Trunking between Cisco and non-Cisco equipment cannot be done.

Answer
c) Nonegotiate

Explanation
To establish a trunk between a Cisco switch and a non-Cisco manufactured device, set the Cisco Catalyst DISL mode to "Nonegotiate." This will force the Cisco Catalyst port to trunk mode while suppressing DISL frames from being sent to the corresponding trunk port on the non-Cisco switch.

Trunking must be enabled manually on the non-Cisco switch to ensure that the trunk link becomes active.
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Question 3.
In a network environment consisting solely of Cisco Catalyst switches, which of the following protocols may be used to enable the transport of multiple VLANs over an Ethernet trunk?
(Choose 2)

a) VLAN Trunk Protocol
b) Inter-Switch Link
c) Dynamic Inter-Switch Link
d) IEEE 802.1Q
e) IEEE 802.1D Spanning Tree Protocol

Answer
b) Inter-Switch Link
d) IEEE 802.1Q

Explanation
Cisco supports two separate VLAN tagging protocols: IEEE 802.1Q and its own proprietary Inter-Switch Link (ISL). Both protocols attach a unique identifier tag containing a VLAN Identifier field to each frame received by a switch. How and where the VLAN identifier is added differ between the protocols.

The identifier tag remains with the frame as the frame moves within the switch fabric of the network. The receiving switch requires some method by which to determine which VLAN the frame belongs, since the trunk link is able to carry frames from all VLANs unless otherwise configured. By tagging the frame with the VLAN from which the frame originated, the receiving switch is able to decode the VLAN identify of the frame.

Neither VTP (responsible for maintaining VLAN configuration consistency on a network-wide basis), DISL (responsible for auto-negotiation of ISL trunk links), nor IEEE Spanning Tree Protocol (responsible for ensuring a loop-free topology) implement any mechanisms that enable the transport of multiple VLANs over an Ethernet trunk.
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