Part 2:
Introduction to IOS:
IOS is the internetwork Operating system that provides an operating system for cisco routers

IOS allows you to change what the router does.
IOS also runs on CISCO managed switches, and this will also aloow us to change what they do as well.

How does CISCO router number their interfaces, this is because we can have several of the same kind of interface in the same router.

CISCO equipment has a numbering scheme based on either fixed configuration or the position of an interface card in a slot

Even though we can look at alot of things when we're in privileged exec mode, we still cant change much. TO CHANGE THINGS, WE NEED TO SWITCH TO CONFIGURATION MODE.

BASIC CONFIGURATION COMMANDS

Hostname

If you type "hostname testing" at the configuration prompt, you'll change the router's name. What has happened to the configuration prompt?

it has changed from router15 to testing

Router

This is a router, so why don't we try turning routing on? (This isn't going to work properly but it will illustrate the point.) Type router rip at the configuration prompt.

What has happened to the configuration prompt?
It has changed to testing(config-router)

Type exit, then change the hostname back to what it was when you started. Then type CTRL-Z or exit then [enter] to exit configuration mode.

What does the prompt look like now?
It looks the same as previous now













CNA part 3:
How IP works, switches works by sending frams out from ports, but the frames are addressed using a MAC address. A mac address is unique to a given network card or a computer.

IP assigns a logical address to a networked device, IP addressing is hirechical, which means that we can go looking for an address based on where it should be, rather than shouting across the world looking for someones computer. The IP address associated with a router will allow us to find it.

router uses ARP to find the right mac address of the client with the target ip address.

3.2 IP routing
route is an instruction on a router that tells that router how to send the packet to its destination. TO achieve this, router must know,

destination address of packet
which of its neighbour router have knowledge about remote networks
possible routes to remote networks
best route to a remote network
how to keep track of the routing information

TWo ways a router can find out about remote networks
-neighbour routers
-network administrators

static router is we set a route by hand, dynamic router is  when the router communicates with another router and finds out about networks from the other router

router uses a routing table to keep track of which routes are associated with which interface. Both approaches make changes to the routing table

3.3 IP addressing
IPV4 is made up of 4 bytes, called octets. Often written with dots between them, dotted notation. A byte can have vales from 0 to 255, so the IP range is 0.0.0.0 to 255.255.255.255, Some have special meaning.We split the ip address into two portion.

For eg, every ip address inside the university is 129.127.xxx.xxx

Address classes:
A: first byte of address and last 3 bytes for host address, 0 to 127
B: first two byte of address and last two byte of address for host, 128 to 191
C: first 3 bytes and last byte for host address, 192 to 223
D is for multicast network and E is for reasearch

Special ip address:
all 0's means any host on this network
all 1's mean all host on this network

Why use different classes?
different classes may have unbalance bytes in the whole IP address, for eg, uni adelaide server is in class B but because UOA is only using one number in the first two bytes. But class A will have less network to use and too many host, or class C will have too many netowrk and too less host to use.

So, we have classes to seperate networks. We can group hosts into subnets, however we do it.

we can logically group our computing resources in an efficient way and make good use of ip address space. The most important reason is that we can use subnetting to reduce traffic on a network. For eg, if a network is very big, then the broadcast messages would cause a heavy load on the routing backbone

So, in summary, here are four good reasons to subnet below the class level:

    Reduced Network Traffic
    Better Network Performance
    Simplified Management
    Big World-Spanning Networks Cost A Lot

3.4 Subetting
subnet mask

refer back to slides if there are problems that i dont know. Overall, i understood all

3.5 refer back to slides if there are problems that i dont know. Overall, i understood all

3.6Creating failover inerfaces and sharing a physical interface over multiple networks

Failover interfaces are when the main interface fails, and the failover interface acts as a backup interface.

To set up a backup interface:

    -Decide which interface will act as the main/primary interface, and which interface will be the secondary/backup interface.
    -Configure and bring up the primary interface as normal.
    -Configure the secondary interface with the same settings as the primary interface but leave it down (i.e. don't run no shutdown)
    -Assign the secondary interface as a backup to the first

steps 2 and 3 should be familiar. To complete step 4, enter config mode , and config the main interface, (0/0 should be the primary one)

"interface GigabitEthernet 0/0"

"backup interface GigabitEthernet 0/1"
This is to specify which is the backup interface.

then we can exit config mode.

Note:
backup interface dont need to have the same ip address as the primary interface to work

in cisco commands, to disable the backup interface, enter config mode for primary interface and use the same commmand but with a "no" added in front

Sharing a physical interface over multiple networks
For eg, this allows staff and students to be connected through the same switches and routers as each other but yet be on different networks with different address ranges.

CISCO routers provide sub-interfaces. These are interfaces that can be configured beneath a physical interface, this feature provided by CISCO routers can be used to provide a virual LAN. These are expressed as "physical_interface.sub_interface".

To configure a sub-interface,

1. Choose a number for subinterface, value 1 and 4 billion
2. Enter interface config mode for the subinterface.
	interface GigabitEthernet 0/0.1
3. then assign a network-unique VLAN ID between 1 and 1001.
	encap dot1q 10
4. Set address for the interface.
	ip address 192.xxx.xxx.xxx 255.255.255.xxx
5. bring interface up
	no shutdown
6. exit
	exit

Uni's switches are configured for vlan id of 1 to 20 only.