Session 4 Flashcards
Vlans - Trunk - NAT
why do you create vlans?
isolate network Group users together enhance security increase traffic flow it is scalable
what is ACL used for
allow/deny access to subnets/host.
If PC1 on vlan 1 and PC3 on vlan 3 - can they talk? if so what do you need to to allow that
it will need a router
will a switch forward a packet that is destined to a different vlan
NO - Router do that
what is the total # of vlans
1 thru 4094
vlans #2 - 1001 are consider what?
standard type vlans
vlans #1006 - 4094 are consider what?
extended type vlans
If a switch gets a frame for a vlan it does not know about, what does it do?
Traffic is dropped.
where is vlan stored?
vlan.dat in flash. It is not stored in running or start so not in nvram.
what is a trunk port
allow interface to essentially make virtual tunnels for each vlans is allowed.
what command you can use to see vlan and trunking info
show interfaces ### switchport
what type of encapsulations do cisco switches support?
ISL (inter switch link) and 802.1q which cisco recommends
how does the switch know what vlans belongs to?
802.1q - adds a tag (4 byte to frame)
how can see native vlan?
show interfaces trunk
why does native vlan exist and what is it use for?
only used in 802.1q.
at one point in time, not everything could be tag. so if traffic could not be tag it still could go through the trunk port untag.
if you change the native vlan on 1 switch, what else do you need to do?
match on both sides.
Native vlan should never be what #
vlan 1.
config t
vlan 99
name v99-Native
go to the turnk port
int ###
switchport trunk native vlan 99
end
show int ### switchport - you will see trunk info
how do you get the sys log
config t
terminal monitor
how to prevent from an access port to send DTP messages?
you have to change the administrative mode to static access. This will prevent all the access ports from converting to a trunk port.
command:
config t
int range int#####
switchport mode access
how to do you convert administrative mode on a trunk port from dynamic access to static
put in following command:
switchport nonegotiate
the max # of vlans on any given switch is determine by what?
Switch
STP version
VTP version
IOS / Switch and protocols working on that switch
Interface will not show up under show vl br for 2 reason. what are they?
If the port is trunk and if the vlan has been removed
Each vlan has its own unique what?
subnet
what is required to forward traffic between vlans
router
vlans create their own what?
broadcast domain or segments