Troubleshooting commands of Networking
1. Ping loopback
2. Ping NIC
3. Ping default gateway
4. Ping remote device
Windows DOS Troubleshooting Commands
ping 127.0.0.1
tracert
ipconfig/all
arp -a
Cisco IOS Troubleshooting Commands
ping 127.0.0.1
traceroute
IP CLASSESS:
Class A - 1-126 - network.node.node.node
Class B - 128-191 - network.network.node.node
Class C - 192-223 - network.network.network.node
Private Address Range
Class A - 10.0.0.0 - 10.255.255.255
Class B - 172.16.0.0 - 172.31.255.255
Class C - 192.168.0.0 - 192.168.255.255
OSI Model
Application - Identifying and establishing the availability of intended communication partner and
whether there are sufficient resources
Presentation - Data translation, encryption, code formatting
Session - Setting up, managing and tearing down sessions. Keeps application’s data separate
Transport - Provides end-to-end transport services - establishes logical connections
between hosts. Connection-oriented or connectionless data transfer.
Network - Manages logical addressing and path determination
Data Link - Provides physical transmission of data, handles error notification, flow
control and network topology. Split into two sub layers (LLC and MAC)
Physical - Specifies electrical, mechanical, procedural and functional requirements for activating, maintaining
and deactivating a physical link.
Cisco 3-Layer Hierarchical Model
Core - Backbone connectivity , common for all users, needs to be as fast as possible and fault tolerant, avoid ACL, VLAN trunking and packet filtering
Distribution - Routing - provides access control policies, filtering, WAN access and VLAN trunking
Access - Switching - User and workgroup access, segmentation
OSI Model vs. TCP/IP Model
FTP - TCP file transfer service – port 20-21
Telnet - Terminal emulation program – port 23
TFTP - UDP file transfer – port 69
SMTP - Send email service – port 25
DHCP – Assigns IP addresses to hosts –ports 67 and 68
DNS – Resolves FQDNs to IP addresses –port 53
Host-to-Host layer
TCP - Connection-oriented protocol, provides reliable connections
(acknowledgments, flow control, windowing)
UDP - Connectionless protocol, low overhead but unreliable
TCP/IP Model Protocol Suite Internet layer
IP - connectionless protocol, provides network addressing and routing
ARP - finds MAC addresses from known IPs
RARP - finds IPs from known MAC addresses
ICMP - provides diagnostics, used by ping and traceroute Network Access
CIDR BASICS
255.0.0.0 /8
255.128.0.0 /9
255.192.0.0 /10
255.224.0.0 /11
255.240.0.0 /12
255.248.0.0 /13
255.252.0.0 /14
255.254.0.0 /15
255.255.0.0 /16
255.255.128.0 /17
255.255.192.0 /18
255.255.224.0 /19
255.255.240.0 /20
255.255.248.0 /21
255.255.252.0 /22
255.255.254.0 /23
255.255.255.0 /24
255.255.255.128 /25
255.255.255.192 /26
255.255.255.224 /27
255.255.255.240 /28
255.255.255.248 /29
255.255.255.252 /30
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