Follow herierchy when you connect the routers!
RIP: Routing Information Protocal!
Automatically desides, if you have multiple paths, then it selects the shortest
path based on the HOP count!
Host path is setted to 0. (for some reason!) during the RIP configuration! I
think , it means! If I place O in the host that it finds all the networks in the
system by itself!
This way that the router can find itself! Just give the all netwroks to router (for
doing it fast in the exam to save time)
In Packet Tracer, we connect PCs → Switches → Routers (though switches can be
skipped for small labs). Routers connect different networks, but by default they
don’t know about each other’s networks. To make them share, we use RIP (Routing
Information Protocol). RIP automatically finds the best path based on hop count.
During configuration, instead of entering host IPs, we enter the network addresses.
That way, the router advertises its networks and learns others automatically. This
saves time and makes exam labs easier.
🌐 The 7 Layers of OSI – Quick Summary Table
Layer (Top→Bottom) Main Job Example
7. Application User interface; software that talks to the network. Web browser
(HTTP), Email (SMTP)
6. Presentation Data format & translation; encryption, compression. JPEG,
SSL/TLS encryption
5. Session Starts/ends communication sessions between devices. Session control in
video calls
4. Transport Reliable delivery, error checking, segmentation of data. TCP
(reliable), UDP (fast)
3. Network Routing packets from source to destination. IP addresses, Routers
2. Data Link Physical addressing (MAC), error detection in frames. Ethernet,
Switches
1. Physical Actual hardware signals. Cables, Wi-Fi radio waves
Layer Key Concept You Should Know
4 – Transport End-to-End Delivery. Breaks data into segments. Controls
reliability. TCP: Reliable, ordered, error-checked (web, email). UDP: Fast, no
guarantee (gaming, streaming).
3 – Network Addressing & Routing. Chooses the best path for packets across
networks. IP addressing (IPv4/IPv6), Routers, Subnetting.
2 – Data Link Direct Node-to-Node Transfer. Deals with MAC addresses and
frames. Switches, Ethernet, ARP, detecting collisions.
1 – Physical Signals & Hardware. Moves bits as electrical, light, or radio
signals. Cables (fiber, copper), NICs, Wi-Fi antennas.
🔹 Which layer encrypts data? → Presentation (Layer 6)
🔹 Which layer decides the route for packets? → Network (Layer 3)
🔹 Which layer ensures reliable delivery? → Transport (Layer 4)
🔹 Which layer uses MAC addresses? → Data Link (Layer 2)
🔹 Which layer sends actual bits/signals? → Physical (Layer 1)
OSPF - Open Shortest Path First
it dynamically selects the shortest path - dijistra Algorithum
bandwirth is inversely proportional to cost! And the path with the lowest cost is
the shortest one
it loads balance! Bacially avoids to put load on a single path
classless ?
Routing Table - When we do not apply the protocol to a router! The router has
intial information of it's nabeigors in a table! When we connect them they share
there table information with each other! And the routig table of each router has
the complete information of each router in the circuit
#show ip route
LSDB - LINK STATE DATA BASE
Here we don't broad cast information
It has seven Stages
Subnet Mask chainging comes in this
"https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13685-
13.html"
Incremental Link State entoligment / advertisment
Problems in this OSPF:
MySql algorithm runs too many times!
Data is too big and hard to manage
Solution : Divide and conqure ! Make small posts that have it's own small database
so the the SPF (shortest path finder) not many times
Subnet Mask , Wild Card mask(Reverse of subnet mask)?!
199 page
LAB A1 Notes!
IPv4 means there are 4 classes of nerworks!
Class A,B,C,D and E (for future use!)
Class A
First Octet Range: 0-127
Purpose: Designed for very large networks with a large number of hosts.
Class B
First Octet Range: 128-191
Purpose: Intended for medium-sized networks with a moderate number of hosts.
Class C
First Octet Range: 192-223
Purpose: Used for smaller networks, such as home and small business networks.
Class D
First Octet Range: 224-239
Purpose: Reserved for multicasting, a special type of one-to-many communication,
and not for general use.
Class E
First Octet Range: 240-255
Purpose: Reserved for future use or experimental purposes and is not available for
public use on the internet.
First Octect 192 means that it is a class C network!? That means it can hold 256
IP's but actually 2 IP's are reserved,
.0 = Network ID
.255 = Broadcast address
So usable host IPs are .1 to .254.
That’s 254 devices max per subnet.
0.0.0.255 is called a wildcard mask (opposit of subnet mask!)
Each “255” means those bits are fixed — they identify the network.
Each “0” means those bits can change — they identify the host.
When used in DHCP or Interface Configuration,
255.255.255.0 tells the router:
“I’m working with this exact subnet — hosts can vary only in the last octet.”
But in OSPF : network 192.168.10.0 0.0.0.255 area 10
Include all interfaces whose IPs match the first 3 octets (192.168.10) —I don’t
care what the last octet is.
0.0.0.255 means “match all IPs from .0 to .255.”
Mask Type 0 means… 255 means…
Subnet Mask(255.255.255.0) host bits (changeable) network bits (fixed)
Wildcard Mask(0.0.0.255) network bits (fixed) host bits (changeable)
