8 - Advanced Switching Concepts Flashcards
What is a LAN?
a set of devices in a single broadcast domain
What are some benefits of VLANs?
- reduce the number of broadcast domains
- increase security because traffic is not seen by another vlan unless its routed
- qos can be maintained for each vlan
What is the routing of packets between VLANs
intervlan routing
Why should subnets used by vlans on your network be contiguous?
to facilitate route summarization
What are valid vlan ids?
1 - 4094
What vlan ids are reserved?
0 hidden system use
1002 - 1005 token ring and fiber distributed data interface
4095 hidden system use
What command can be used to show a brief summary of vlans on a switch?
show vlan brief
What type of port carries traffic for only one vlan?
access port
what command is used to set the access vlan back to its default?
no switchport access vlan
What is the command to dynamically map mac addresses to a vlan?
switchport access vlan dynamic
What type of port carries traffic from multiple vlans?
trunk port
What are the two trunk encapsulation types?
ISL or inter switch link
802.1q
How do you identify the vlan that a frame belongs to/
a tag
Describe ISL encapsulation.
cisco proprietary ecapsulation that encapsulates each from inside of a 26 byte ISL header and 4 byte crc trailer
Describe 802.1q encapsulation.
standards based trunking protocol developed by IEEE that inserts a 4 byte vlan field into the frames existing ethernet header
What encapsulation method has support for a native vlan?
802.1q
What is the outcome for a native vlan mismatch?
traffic sent to an incorrect vlan
cdp errors
What needs to match on both sides of a trunk link?
native vlan
trunking mode
trunk encapsulation
allowed vlan ids for the trunk
What command is useful in providing a variety of helpful output for both access and trunk ports?
show interfaces fa0/0 switchport
What command is useful in verifying trunk ports?
show interfaces fa0/0 trunk
What is useful about the show interfaces fa0/0 trunk command?
you can see the allowed vlans for a trunk
Why is voice traffic usually separated from data traffic?
for performance purposes
What happens when the voice vlan is configured on a port?
portfast is automatically enabled
how do you enable qos on the voice vlan?
trust device cisco-phone
What is the limitation for port-security on a voice vlan?
You cannot statically configure mac addresses on a voice port, you have to use the maximum 2 command at a minimum
What command causes the ip phone to use 802.1p tagging with a priority of 5 instead of 802.1q causing it to transit over the native vlan?
switchport voice vlan dot1p
What command causes the ip phone to behave as if it were not connected to a switch, using its own config and traversing the access vlan?
switchport voice vlan none
What command causes the ip phone to send untagged voice traffic just as if the switchport voice vlan command was not used?
switchport voice vlan untagged
How do you disable DTP?
switchport nonegoiate
What is ciscos recommendation for trunk links?
set both sides of the trunk to dynamic desirable when using DTP
What are different modes of a switchport?
access
trunk
dynamic desirable
dynamic auto
What is dynamic desirable?
a port that will actively negotiate to become a trunk port
What is dynamic auto?
a port that will no actively negotiate to become a trunk port
What is the outcome if you have two switchports that are configured for dynamic auto?
they will be access ports and not trunk ports
What is the outcome if you have two switchport that are configured for dynamic deseriable?
they will be trunk ports
What is the outcome if you have one switchport as dynamic auto and one switchport as dynamic desirable?
they will be trunk ports
What layer does vtp operate at?
Layer 2
What are the requirements for VTP to operate?
switches must be connected over a trunk
vtp domain must match
vtp password must match
vtp version must match
what is the default vtp domain name?
NULL
how many vtp domains can a switch belong to?
one
What happens to a switch that is configured for the NULL domain receives a vtp advertisement with a different vtp domain name?
it will change its vtp domain to match
What vtp version is configured by default?
vtp version 1
What happens if a vtp version 1 switch receives a vtp version 2 advertisement?
the switch will change to version 2 if it is supported on that swithc
What is the default vtp mode of cisco switches?
server mode
Where do vtp version 3 clients store their vlan configuration?
NVRAM, vtp version 1 and 2 clients do not keep the vlan configuraton
What does vtp transparent mode do?
Transparent mode will forward vtp advertisements, but not update its own vlan table. Transparent mode keeps its local vlan configuration in nvram
How often do vtp servers and clients flood their advertisements?
every 5 minutes or when a change is made
What vlan is used for vtp advertisements?
vlan 1
How do switches keep track of the changes to the vlan database?
incrementing the configuration revision number
Can a vtp client cause a vtp server to be updated?
Yes, if the clients revision number is higher than the servers revision number
What is the revision number of a vtp transparent switch?
revision 0
How do you delete the vlans on a switch?
deleting the vlan.dat from flash or nvram
what is vtp pruning?
prunes vlan traffic to switches that are not participating in a particular vlan
Is vtp pruning enabled by default?
its disabled by default
How do you configure vtp pruning?
global configuration mode, vtp pruning
How can you have intervlan routing when you only have layer 2 switches?
using router on a stick
