Organizations are “assigned” a network address to use on the internet
216.93.144.0/20
All champlain IPs start with the same 20 bits
Last 12 bits are used for host ID
2^12 IPs can be used
All zeros and all 1’s in the host ID can’t be used
But a /20 network cna support 4094 hosts - do we want them all on the same network?
Lots of broadcast packets congest the network
Machines are slowed by trying to process them
Anyone can contact anyone else on the network!
Our network ID can’t change but what if we took some host ID bits to create a subnet ID
These bits are then ”added” to the network ID
For example if we used 4 bits for the subnet ID
Wireless networks are normally larger networks because most devices are looking for information outside the network. Larger network means less communication inside the network.
Smaller networks are found in places where devices communicate within the network. For example a data center. (Network to Network firewall rules instead of Host to Host rules)
Always start with the largest subnet first: Larger subnet boundaries are always valid for smallers ones, but smaller boundaries are not always valid for larger ones
All 0’s in the Host ID refers to the Network itself - cannot be assigned to a host
All 1’s in the Host ID is the broadcast -cannot be assigned to a host
So if we have n bits in our Host ID, we can assign 2^2 -2 IP addresses\
VLANS
Multilayer switching
A virtual LAN is a group of devices on one or more physical LANs that are configured to communicate as if they were on the same LAN.
VLANs define broadcast domains in a Layer 2 network
Need a router to pass packets between 2 different VLANs
Access Ports: Can only be assigned to/carry traffic from a single VLAN
Used to connect end device to a switch
Trunk Ports: Carry traffic from multiple VLANs - used to connect switches
Will “tag” packets with the proper VLAN ID\
CISCO IOS Config File
Startup-config: This is the last version that was saved. If the router/switch was restarted, this is the config that would load
Running-config: Whats running in memory. It has all of the config changes made at the command line since it was last saved.
User EXEC Mode: Basic monitoring and status commands
Prompt it: router>
Type enable to get to Privileged
Privileged EXEC Mode: Administrative access
Prompt: router#
Type config to get to the config mode
Config EXEC MODE: config mode
Prompt: router(config)#
The question mark ?:
Just hit enter and it will show everything you can do