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40 Cards in this Set
- Front
- Back
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Five reasons for using VLANS |
1. Segment into smaller LANs;
2. Better security; 3. Separate voice and data traffic; 4. Reduce STP workload; 5. Group users by dept not location |
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Name the two VLAN trunking protocols. Who defined each?
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ISL (Cisco) and 802.1q (IEEE) |
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Describe ISL trunking protocol
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Defined by Cisco; Encapsulates original frames; does not use native VLAN
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Describe 802.1q trunking protocol
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IEEE; Adds 4 bytes to the original frame header; does not encapsulate; uses native VLAN
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Which VLAN trunking protocol encapsulates the original frame?
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ISL
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What is the "Normal Range" for VLAN numbers
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1 to 1005
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What is the extended range for VLAN numbers
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1006 to 4094
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Which trunking protocols support multiple instances of STP?
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Both ISL and 802.1q
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Name the three VTP modes
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Server, client, and transparent
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When do VTP changes propagate to the network?
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Changes propagate immediately. Servers and clients also send periodic messages every 5 minutes.
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Three requirements for VTP to work between two switches
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working VLAN trunk link; case sensitive VTP domain name must match; cast sensitive VTP password must match, if one exists.
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Where is VTP configuration stored?
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flash:vlan.dat; note: transparent mode stores in running-config
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What does VTP transparent mode do with VTP update messages?
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forwards them to other switches
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What does VTP pruning do?
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Uses VTP to automatically prune; do not send unneeded VLAN frames out trunks
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Can you configure VLANs from the CLI on a client-mode switch?
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No
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CLI mode and command to configure a VLAN
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configuration mode;
#vlan [name ] name parameter may also go on next line. |
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CLI mode and command to configure a VLAN on an interface
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interface mode;
#switchport access vlan |
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Default VTP mode, VLANs, on a Cisco switch
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VTP server mode;
no VTP domain name, VLAN 1 and 1002-1005 automatically configured, all access interfaces assigned to VLAN 1 |
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CLI command to show basic vlan info
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#show vlan brief
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CLI command to set a range of interfaces to a certain vlan
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#interface range fa0/10 - 20
#switchport access vlan |
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Name four switchport modes
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access
trunk dynamic desirable dynamic auto |
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CLI command to set switchport mode
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#switchport mode
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CLI command to show switchport modes
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#show interfaces switchport
#show interfaces Gi0/1 switchport |
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CLI command to allow specific vlans over a trunk
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#switchport trunk allowed vlan {add | all | except | remove} vlan-list
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Four reasons why a certain vlan would not cross a trunk
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1. removed from the allowed list
2. does not exist or is not active in switch's vlan.dat 3. automatically pruned by vtp 4. trunk not in forwarding state |
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CLI to show which vlans are allowed over a trunk
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#show interfaces trunk
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CLI command to configure voice vlan on access interface
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#switchport voice vlan
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Why is it necessary to secure unused ports on a switch?
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Attacker could connect to port, negotiate trunking, mess up VTP database
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Cisco recommendations to protect unused ports (3):
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shutdown
switchport mode access or switchport nonegotiate switchport access vlan |
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CLI commands to configure VTP
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#vtp mode [server | client]
#vtp domain #vtp password #vtp version 2 (optional) |
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CLI command to configure vtp pruning
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#vtp pruning (only on servers)
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CLI command to see VTP status
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#show vtp status
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CLI command to see vtp password
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#show vtp password
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VTP troubleshooting steps
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1. verify vtp modes
2. verify working trunk(s) 3. verify vtp domain name and password; |
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When two switches connect, which VTP database will be used?
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The one with the higher VTP version number
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How to set VTP version number back to zero
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#delete flash:vlan.dat
or set mode to transparent then back to server/client |
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What can cause slow intraVLAN connectivity? 7 items.
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Traffic loop
Oversubscribed VLAN Congestion on switch inband path High CPU use on switch Hardware or software misconfiguration Software bugs Ingress errors on a cut-through switch |
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What can cause slow interVLAN connectivity? 3 items.
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User misconfiguration
Failure in programming shortcuts Hardware malfunctions |
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VTP: CLI command to show allowed VLANs on a particular trunked interface
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#show interfaces trunk
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VTP: Does a switch in default configuration advertise VTP updates? Why/Why not?
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No. Even though the switch will be in server mode, it has a blank domain name. It will not send updates until a domain name is configured.
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