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Answers to the Chapter 4 "Do I Know This Already?" Quiz 717
10
Describe the benefits of creating three VLANs of 25 ports each, versus a single VLAN of
75 ports, in each case using a single switch. Assume that all ports are switched ports (each
port is a different collision domain).
Three different broadcast domains are created with three VLANs, so the devices' CPU
utilization should decrease due to decreased broadcast traffic. Traffic between devices in
different VLANs will pass through some routing function, which can add some latency
for those packets. Better management and control are gained by including a router in the
path for those packets.
11
If two Cisco LAN switches are connected using Fast Ethernet, what VLAN trunking
protocols could be used? If only one VLAN spanned both switches, is a VLAN trunking
protocol needed?
ISL and 802.1Q are the trunking protocols used by Cisco over Fast Ethernet. If only one
VLAN spans the two switches, a trunking protocol is not needed. Trunking or tagging
protocols are used to tag a frame as being in a particular VLAN; if only one VLAN is used,
tagging is unnecessary.
12
Define the term VLAN.
Virtual LAN (VLAN) refers to the process of treating one subset of a switch's interfaces
as one broadcast domain. Broadcasts from one VLAN are not forwarded to other VLANs;
unicasts between VLANs must use a router. Advanced methods, such as Layer 3 switching
in a NetFlow feature card in a Catalyst 5000 switch, can be used to allow the LAN switch
to forward traffic between VLANs without each individual frame being routed by a router.
However, for the depth of CCNA, such detail is not needed.
13
How many IP addresses must be configured for network management on a Cisco Catalyst
1900 switch if eight ports are to be used with three VLANs?
A single IP address is needed. There is no need for an IP address per port because the
switch is not a router. The management IP address is considered to be in VLAN1.
14
What Catalyst 1900 switch command displays the version of IOS running in the switch?
This is a trick question. The show version command shows the level of switch software,
but because the switch does not run IOS, no command will display the level of IOS in the
switch.
15
Configuration is added to the running configuration in RAM when commands are typed in
Catalyst 1900 configuration mode. What causes these commands to be saved into
NVRAM?
Unlike the router IOS, commands are saved in both running config and in NVRAM as the
user enters the configuration commands. No separate command, such as copy running-
config startup-config in the router IOS, is needed.
apA.fm Page 717 Monday, March 20, 2000 5:24 PM