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ROM: Read Only Memory. bootstrap startup program. operating system software. power on diagnostic test program.
POST: Power On Self Test
Flash Memory: ios image here. erasable reprogrammable rom.
RAM: Random Access Memory. stores operational info such as routing/switching tables and running config file. it is lost when router powered down or rebooted.
NVRAM: non volatile ram. holds router startup config file. contents are not lost on rebooting. NV(never)
r1(config)# cdp run
cdp run … cdp is usually turned on but if it’s not the command above turns it on
r1(config)# show cdp neighbors
shows you what it’s plugged into
Only cisco devices.
Link Layer Discovery Protocol
LLDP
r1(config)# lldp run
This one is not usually turned on so you have to manually turn it on.
shows you what it’s plugged into
All devices. IEEE standard.
r2(config)# hostname r2
r2(config)# ip domain-name ccna.class
r2(config)# crypto key generate rsa
r2(config)# r2.ccna.class
r2(config)# line vty 0 1
r2(config-line)# transport input ssh
logging in
Putty
ssh -l name x.x.x.x
password:
Trunking is the process of creating logical connection between two physically connected switches allowing frames to flow between them.
Members of same VLAN communicate when physically attached to different switches.
ISL: cisco proprietary. encapsulates the entire frame before sending it across the trunk. results in greater overhead than ieee 802.1q. does not recognize native vlan
dot1q: industry standard. does not encapsulate frame. inserts 4byte value with vlan id in ethernet header. recognize native vlan.
native vlan: default vlan. usually vlan 1.
Dot1Q will not put 4byte value into ethernet header if frame is destined for native vlan. When remote switch receives an untagged frame and it knows it is destined to native vlan frame is forwarded to ports belonging to that vlan.
Vlans help us group hosts by whatever category.
Vlans allow you to increase security by hiding logical group of hosts from everyone else you want.
Prevents broadcast storms.
Broadcast storms slow network performance down a little, little more, little more and prevents basic switching functions.
IP address run at layer three.
Lab Example
If your on host one and you
host1# show cdp neighbor
You’ll see your physical connections.
Switch1
Log on to switch1
switch1# show cdp neighbor
See all of your connections.
show vlan will give you info you need.
switch1#
switch1# config t
switch1#(config) #int fast 0/2
switch1(config-if)# switchport access vlan 24
this is creating vlan 24
switch1#(config) #int fast 0/4
switch1(config-if)# switchport access vlan 24
switch1#show vlan brief
You’ll see it was created
Draw the line where the numbers differ.
Count out the bits.
That’s your CIDR.
Write out the beginning as the address and the bits as the cidr.
Check out this document.
I Found These Images Very Helpful
Best Video for Learning Subnetting
Classes
A –Â Private – Not routable on the internet
B
C
Bit Values
128Â Â Â 64Â Â Â 32Â Â Â 16Â Â Â 8Â Â 4Â Â Â 2Â Â Â 1
xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx
CIDR – how many bits on. each x is a bit
Network is everything that is on.
Host is everything that is off.
Hosts are numbers on the right subtract 2.
Subnets are from left to right and count how many bits.
Example Breakdown:
192.168.100.97 /27
255 . 255 . 255. 111|00000
1 1 1 0 0 0 0 0
|128 64 32|
32 is increment
x.x.x.32
x.x.x.64
x.x.x.96 +31 = 127
96 subnet
broadcast 127
Examples Breakdown:
255.255.254.0
x.x.11111111|0.0
2 4 8 16 32 64 128
512 – 2 = 510
BIT =Â Decimal
1Â Â =Â Â 128
2Â Â =Â Â 192
2Â Â =Â Â 224
4Â Â Â =Â Â 240
5Â Â Â =Â Â 248
6Â Â Â =Â Â 252
7Â Â Â =Â Â 254
8Â Â Â =Â Â 255
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