Module 9: Address Resolution (from "Computer Networks -
09.pptx")
1. MAC and IP Addressing:
○ Same Network:Devices on the same Ethernet LAN usetheir
Layer 2 MAC addresses to communicate directly.(howLAN
parties work)
○ Remote Network:If the destination is on a differentnetwork,
the device uses the MAC address of the default gateway (router)
to forward the packet to the remote network.(thisis why we
port forward so the router knows where to sent the data
packages to which local device instead of the many users on the
same public ip address)
2. Address Resolution Protocol (ARP):
○ Purpose:ARP is usedto map a known IPv4 address toa MAC
address(relationship between them), enabling communication
over Ethernet.
Just a more specific version of each other
○ How ARP Works:
■ The sender broadcasts an ARP request to all devices on the
local network, asking for the MAC address of the target
IPv4 address.
■ The device with the corresponding IPv4 address replies
with its MAC address, allowing the sender to create an ARP
table entry.
○ ARP Table:Maintains mappings of IPv4 addresses toMAC
addresses. Entries in this table are aged out after a period or can
be manually cleared by an administrator.
, ○ Problems with ARP:
■ Excessive Broadcasts:ARP broadcasts (why are there
broadcasts)can overwhelm the network if there aremany
devices.
Doofus just read the part above the text if youneeded to know
■ Security Vulnerabilities:ARP is vulnerable tospoofing
attacks, where a malicious device sends false ARP
messages to associate its MAC address with the IP address
of another device.
3. IPv6 Neighbor Discovery (ND):
○ Functions:Performs thesame function as ARPbut usesICMPv6
messages.
○ Messages:
■ Neighbor Solicitation (NS):Sent by a device to discover
the MAC address of another IPv6 device on the same
network.
■ Neighbor Advertisement (NA):Response from the
device being queried, providing its MAC address.
○ Router Discovery:Uses Router Solicitation (RS) andRouter
Advertisement (RA) messages to locate routers on the local link.
, Module 10: Basic Router Configuration (from "Computer
Networks - 10.pptx")
1. Initial Router Configuration:
○ Steps:
■ Configure Device Name:Assign a unique hostname to
identify the router in the network.
enable secretto
■ Secure Privileged EXEC Mode:Use
set a secure password for privileged EXEC mode.
■ Secure User EXEC Mode:Configure a password for
line console 0
console access using password
, , and
logincommands.
■ Secure Remote Access (Telnet/SSH):Set up
line vtyand specifythe
passwords for remote access via
transport protocols (
sshor
telnet
).
service
■ Encrypt Passwords:Use the
password-encryptioncommand to encrypt all plaintext
passwords.
■ Legal Notification:Create a Message of the Day (MOTD)
banner motdto display legal warningsor
banner using
notices.
■ Save Configuration:Save the configuration to NVRAM
copy running-config startup-config
using .
2. Basic Router Configuration Example:
○ Commands for Basic Configuration on Router R1:
R1(config)# hostname R1
■ Set hostname:
R1(config)# enable secret class
■ Secure EXEC mode:
R1(config-line)# password
■ Configure console password:
ciscoand
login
09.pptx")
1. MAC and IP Addressing:
○ Same Network:Devices on the same Ethernet LAN usetheir
Layer 2 MAC addresses to communicate directly.(howLAN
parties work)
○ Remote Network:If the destination is on a differentnetwork,
the device uses the MAC address of the default gateway (router)
to forward the packet to the remote network.(thisis why we
port forward so the router knows where to sent the data
packages to which local device instead of the many users on the
same public ip address)
2. Address Resolution Protocol (ARP):
○ Purpose:ARP is usedto map a known IPv4 address toa MAC
address(relationship between them), enabling communication
over Ethernet.
Just a more specific version of each other
○ How ARP Works:
■ The sender broadcasts an ARP request to all devices on the
local network, asking for the MAC address of the target
IPv4 address.
■ The device with the corresponding IPv4 address replies
with its MAC address, allowing the sender to create an ARP
table entry.
○ ARP Table:Maintains mappings of IPv4 addresses toMAC
addresses. Entries in this table are aged out after a period or can
be manually cleared by an administrator.
, ○ Problems with ARP:
■ Excessive Broadcasts:ARP broadcasts (why are there
broadcasts)can overwhelm the network if there aremany
devices.
Doofus just read the part above the text if youneeded to know
■ Security Vulnerabilities:ARP is vulnerable tospoofing
attacks, where a malicious device sends false ARP
messages to associate its MAC address with the IP address
of another device.
3. IPv6 Neighbor Discovery (ND):
○ Functions:Performs thesame function as ARPbut usesICMPv6
messages.
○ Messages:
■ Neighbor Solicitation (NS):Sent by a device to discover
the MAC address of another IPv6 device on the same
network.
■ Neighbor Advertisement (NA):Response from the
device being queried, providing its MAC address.
○ Router Discovery:Uses Router Solicitation (RS) andRouter
Advertisement (RA) messages to locate routers on the local link.
, Module 10: Basic Router Configuration (from "Computer
Networks - 10.pptx")
1. Initial Router Configuration:
○ Steps:
■ Configure Device Name:Assign a unique hostname to
identify the router in the network.
enable secretto
■ Secure Privileged EXEC Mode:Use
set a secure password for privileged EXEC mode.
■ Secure User EXEC Mode:Configure a password for
line console 0
console access using password
, , and
logincommands.
■ Secure Remote Access (Telnet/SSH):Set up
line vtyand specifythe
passwords for remote access via
transport protocols (
sshor
telnet
).
service
■ Encrypt Passwords:Use the
password-encryptioncommand to encrypt all plaintext
passwords.
■ Legal Notification:Create a Message of the Day (MOTD)
banner motdto display legal warningsor
banner using
notices.
■ Save Configuration:Save the configuration to NVRAM
copy running-config startup-config
using .
2. Basic Router Configuration Example:
○ Commands for Basic Configuration on Router R1:
R1(config)# hostname R1
■ Set hostname:
R1(config)# enable secret class
■ Secure EXEC mode:
R1(config-line)# password
■ Configure console password:
ciscoand
login
