DORA

Question 1

DORA

Answer 1

DISCOVER – BROADCAST – (CLIENT) – (looking for a DHCP server)
OFFER – SERVER – UNICAST – (SERVER) – (offering an IP address to the client)
REQUEST – BROADCAST – (CLIENT) – (I want the IP address you offered)
ACKNOWLEDGEMEMNT – UNICAST – SERVER – (confirms the IP address leased to the client)

Question 2

VPNs

Answer 2

VPNs
Encrypts data in a virtual tunnel in the public internet.
2 types
1. Site
2. Remote Access – connects to network using client software (allows employees to access network
from home or on the road)

Question 3

Cloud Services

Answer 3

Cloud Services
SAS – Software as a Service – Software and Applications
PAS – Platform as a Service - platform for developers to build cloud applications
IAS – Infrastructure as a Service - raw computing power for service providers. It can also include the
servers, file or object storage, load balancers, network firewall, CDNs, etc. IaaS providers deliver
these capabilities on-demand from a large cluster of equipment stationed in data centers.
Amazon AWS, Microsoft Azure, Google Compute Engine, Rackspace, and IBM SmartCloud
Enterprise are all leading providers of IaaS, Many big names in SaaS including Dropbox,
Instagram, and Pinterest run on IaaS platforms provided by Amazon and others.

Question 4

VLANS (Virtual LANs

Answer 4

VLANS (Virtual LANs)
VLANs group users by functions or roles.
• Computers can only talk to other computers in their own VLAN unless there is a layer 3 device
configured.
• Computers can only talk to other computers in their own VLAN on their own switch unless a trunk port
is configured and connected to other switches.

Question 5

Switchport Types

Answer 5

Switchport Types
1. Access – connects to end-user devices (hosts)
2. Trunk – connects to another switch or router (necessary for VLAN config)
• Point-to-point connections
• Trunk ports belong to the native vlan – vlan 1 by default – best practice change to
another vlan

Question 6

Frame Sizes

Answer 6

Frame Sizes
802.1Q Protocol (frame-tagging protocol)
• Allows all VLANs to use a trunk line instead of one VLAN per physical interface
• Inserts a 4-byte VLAN ID field if frame must travel over trunked line
• Minimum-sized regular frame = 64 bytes
• Minimum-sized 802.1q frame = 68 bytes
• Maximum-sized regular frame = 1500 bytes (minus header and trailer)
• Baby giant frame = 1518 bytes (maximum sized + header and trailer)
• Maximum-sized 802.1q frame = 1522 bytes
• Jumbo frame - > or = 9000 bytes

Question 7

Port Security

Answer 7

Port Security - Stop rogue devices from accessing your network!

Question 8

Switch Redundancy

Answer 8

Switch Redundancy
Purpose: Eliminate a single point of failure
Problem: Layer 2 broadcast storms/switching loops/flooding frames
Solution:

Question 9

Spanning Tree Protocol

Answer 9

Spanning Tree Protocol (STP – 802.1d)
o PVST+: Cisco-proprietary – STP with extended ID for VLANs
o PVST+ is turned on by default on Cisco switches

Question 10

Rapid Spanning Tree Protocol

Answer 10

Rapid Spanning Tree Protocol (RSTP – 802.1w) – converges immediately
o RPVST+: Cisco-proprietary – RSTP with extended ID for VLANs
o Must turn on RPVST+ on switch

Question 11

Spanning Tree Steps

Answer 11

Spanning Tree Steps
1. Elect a root bridge – BPDUs (bridge protocol data unit) containing BIDs (bridge ID) [priority and MAC
addresses] are broadcasted every 2 seconds
• Root bridge has all forwarding ports and is connected to all forwarding ports
• Default priority – 32768
• All ports on the root bridge are forwarding and designated.
• Each VLAN has its own root bridge.

Question 12

Elect a root port for each non-root switch (lowest cumulative path cost to root).

Answer 12

Elect a root port for each non-root switch (lowest cumulative path cost to root).
• Every non-root switch has a root port.
Bandwidth Cost
10 mbps 100
100 mbps 19
1 gig 4
2 gig 3
10 gig 2