Chapter 9 Flashcards
LAN, according to CISCO
A LAN includes all devices in the same broadcast domain
What do VLANs allow a switch to do?
You can configure the switch to classify interfaces into separate broadcast domains
6 reasons to use VLANs
- To reduce total CPU overhead by reducing the number of hosts that must process brodcasts.
- Reduce security risks by limiting number of hosts that receive broadcasts, multicasts
- Limit exposure of sensitive data
- Create flexible designs based on workplace function, not physical location
- Solve problems quickly, as failure domain often matches the broadcast domain
- Reduce workload for STP by limiting a VLAN To a single access switch
VLAN Trunking
Creating one link between switches that supports multiple VLANS
Two different VLAN trunking protocols
ISL (inter-switch link) and IEEE802.1Q
Theoretical and realistic maximum number of VLANs for 802.1Q
Theory: 4096
Reality: 4094 – Two reserved IDs of 0 and 4095
Number of bits in the VLAN ID field for 802.1Q
12
The normal range for VLANs
1-1005
The extended range for VLANs
1005 - 4094
Native VLAN
Traffic using VLAN 1.
What is not included for the native vlan?
A 802.1Q tag
Devices in different VLANs should be in different ____
subnets
What do you need to do to allow traffic to flow from one vlan to another?
Attach a port from each VLAN to a router, or a layer 3 switch
Access port versus a trunk port
Access ports are used for a single vlan. Trunk ports are used to connect switches. A single trunk port can carry data about multiple vlans
VTP
VLAN Trunking Protocol. An older, CISCO protocol for VLANs that allows switches to advertise VLAN configs
3 modes of VTP
Client, Server, Transparent
DTP
Dynamic Trunking Protocol. Used for Cisco switches to negotiate on which trunking protocol to use
If both cisco switches support both trunking protocols, which one do the switches use, according to DTP?
ISL
5 reasons VLAN traffic may be prevented from crossing a trunk
VLAN has been removed from a turnk’s allowed VLAN list
VLAN does not exist on switch config
VLAN exists, but has been administratively disabled
VLAN has been pruned automatically by VTP
VLAN’s STP instance has placed the trunk interface in a blocking state
