1. Introduction to Networking (Routing & Switching)
Nir Ingbar

2. Agenda OSI 7 Layers model Layer 1 & 2 Frame forwarding & filtering
VLAN, dot1Q Trunking IP
Routing

3. OSI 7 Layers model (1977 by ISO)

4. OSI Model Layer’s definitions
Each OSI layer performs unique and specific task
A layer only has a knowledge of its adjacent layers
A layer uses the services of a layer below
A layer performs functions and provides service to the layer above
A layer service is independent of its implementation
Application
Presentation
Session
Transport
Network
Data Link
Physical

5. OSI Model Layers
Physical: Electrically encodes and physically transfers messages between nodes
Data Link: Provides reliable transit of data across a physical link, handling physical addressing, link discipline, error detection, ordered delivery of frames and flow control
Network: Provides connectivity and path selection between two end systems that may be located on geographically diverse sub-networks
Transport: End- to- end control & information exchange with a level of reliability required for the applications

6. OSI Model Layers (cont.)
Session: Manages the connection between cooperating applications
Presentation: Transforms data to and from negotiated standardized formats
Application: Provides the window between the application process and OSI

7. * FCS (Frame Check Sequence)
Data encapsulation
Data
Application
Application
Data
Presentation
Presentation SH
Data Unit
Session
Session TH
Data Unit
Transport
Transport NH
Data Unit
Network
Network
DLH
Data Unit
FCS
Data Link
Data Link
Bits
Physical
Physical
* FCS (Frame Check Sequence)

8. Internetworking Devices
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Router
Network
Data Link
Switch/Bridge
Data Link
Physical
Hub/Repeater
Physical

9. Ethernet, Token Ring, FDDI,
Protocol Suite
Application
Telnet
FTP
SMTP
TFTP
BOOTP
SNMP
Presentation
Session
Transport
TCP
UDP
Network IP
ICMP
ARP
Data Link
Ethernet, Token Ring, FDDI,
WAN synchronous
Physical

10. Layer 1 & 2

11. Device Types
Hub - multi port repeater, provide connectivity, allowing attached devices a path between which they can communicate, works on layer one
Switch – connecting hosts
Bridge – connecting networks, can’t identify different logical networks

12. Bridge vs. Switch
Bridge usually have two interfaces and can connect to physical networks
Switches usually have more than that
The main difference between a switch and bridge is the number of networks each can connect
Switches are often aimed to connect workstations in a single junction
Both are used inside LAN
Both operates on layers one and two

13. Collision Domain
one of the logical network segments in which the data packets can collide to each other
Collision domains are often referred as ‘Ethernet segments'.
defined as a single CSMA/CD network segment in which there will be a collision if two computers attached to the system both transmit at the same time
A collision occurs when two or more network devices are trying to transmit packets at the exact same time

14. Collision domain - example

15. Collision domain - example

16. Type Of Transmission
Unicast - unicast transmission is the sending of information packets to a single destination
Broadcast - broadcasting refers to transmitting a packet that will be received (conceptually) by every device on the broadcast domain
Multicast - multicast is a network addressing method for the delivery of information to a group of destinations simultaneously
Anycast – like multicast but only one address of a set of addresses is chosen at any given time to receive information from any given sender

17. MAC Address
48 bits (6 octets) address space representing an unique identifier to most network adapters or network interface cards (NIC)
The first three octets identify the organization that issued the identifier and are known as the Organizationally Unique Identifier (OUI)
00-16-D3-C4-55-6A

18. Broadcast Domain
represents the systems to which a given broadcast will travel
broadcasts do not pass routers by default
If one station will broadcast, all the stations in this domain will get the message
If a station wants to send a message out of the LAN, it will have to know it’s Default Gateway

19. Broadcast domain – simple example

20. Collision domain- problem

21. One switch can be a Single Point Of Failure
Adding an additional Switch can create broadcast storm.

22. Solution: STP – Spanning tree Protocol
On running this algorithm the LAN is reduced to an acyclic tree
The main idea of the Spanning Tree is for the bridges to select the ports over which they will forward frames

23. Spanning Tree Protocol
Spanning tree is designed to prevent loops in bridged/switched Ethernet network based on the root bridge concept, which is selected via programmable parameters L4 L3
Actual Network L2 L5 L1 B1 B4 B3 B5 B2
With Spanning Tree B5 B3 L2 L1 L3 L4 L5 B1 B2 B4 X

24. Frame forwarding & filtering

25. Frame forwarding & filtering
The initial MAC address is empty

26. Frame forwarding & filtering (cont.)
Station A sends a frame to station C
The switch caches the MAC address of station A to port E0 by learning the source address of data frames
The frame from station A to station C is flooded out to all ports except port E0

27. Frame forwarding & filtering (cont.)
Station D sends a frame to station C
The switch caches the MAC address of station D to port E3 by learning the source address of data frames
The frame from station D to station C is flooded out to all ports except port E3

28. Frame forwarding & filtering (cont.)
Station A sends a frame to station C
The destination is known; the frame is not flooded

29. VLAN, dot1Q Trunking

30. VLAN, dot1Q Trunking 802.1Q Frame
FCS (Frame Check Sequence) is recalculated

31. Importance of native VLANs
VLAN 1 untagged traffic (native VLAN)
An 802.1Q trunk and its associated trunk ports have a native VLAN value Q does not tag frames for native VLAN. Therefore, ordinary stations will be able to read the native untagged frames, but will not be able to read any other frame because the frames are tagged

32. IP

33. Relies on a transport protocol to guaranty delivery
Internet Protocol - IP
Network Layer
Provides network layer services to TCP/IP protocol suite
Responsible for forwarding packets through network based on IP addresses
“Best effort” delivery
Connectionless
Unacknowledged
Relies on a transport protocol to guaranty delivery

34. IPv4 Addressing
Address format: XXX.XXX.XXX.XXX (0≤XXX≤255)
Addresses are 32 bits long (4,294,967,296 IP addresses)
Internet Assigned Numbers Authority (IANA) assigns IP addresses for the Internet
Divided into five classes three of which are available to end-user networks
Consists Network and Host identification fields

35. Available IP Addresses
Class
Assigned Network/
/Host ID
Range of Network IDs
Max. Hosts
Per Network
A /8
NET.X.X.X
1 –126
16,777,214
B /16
NET.NET.X.X
128.1 –
65,534
C /24
NET.NET.NET.X –
254
Class D is reserved for multicast groups
Class E is reserved for future use

36. Private Networks RFC 1918 addresses RFC 2026—Link Local Addresses
Not routed by Internet routers (filtered by Edge Routers)
RFC 2026—Link Local Addresses –
Auto-assigned IP address to local host if DHCP server cannot be contacted
Not routed by any router
Class
Assigned Network/
/Host ID
Range of Network IDs A
NET.X.X.X B
NET.NET.X.X C
NET.NET.NET.X

37. Other Reserved Addresses–
Reserved for testing and loopback routines for IP Applications
ping —verifies the local host has properly loaded the IP protocol
– —Class D multicast (IANA)
Reserved for well known services and network topology mechanisms

38. Subnetting IP/VLSM/Classless
Allows to divide a single IP network into smaller divisions – Subnets
Done by borrowing bits from the host portion of the address
Subnet bits are defined by the Subnet Mask
IP Address 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Subnet Mask
Or /20 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Subnet Host

39. Summary Host-to-Host Packet Delivery (1 of 22)

40. Host-to-Host Packet Delivery (2 of 22)

41. Host-to-Host Packet Delivery (3 of 22)

42. Host-to-Host Packet Delivery (4 of 22)

43. Host-to-Host Packet Delivery (5 of 22)

44. Host-to-Host Packet Delivery (6 of 22)

45. Host-to-Host Packet Delivery (7 of 22)

46. Host-to-Host Packet Delivery (8 of 22)

47. Host-to-Host Packet Delivery (9 of 22)

48. Host-to-Host Packet Delivery (10 of 22)

49. Host-to-Host Packet Delivery (11 of 22)

50. Host-to-Host Packet Delivery (12 of 22)

51. Host-to-Host Packet Delivery (13 of 22)

52. Host-to-Host Packet Delivery (14 of 22)

53. Host-to-Host Packet Delivery (15 of 22)

54. Host-to-Host Packet Delivery (16 of 22)

55. Host-to-Host Packet Delivery (17 of 22)

56. Host-to-Host Packet Delivery (18 of 22)

57. Host-to-Host Packet Delivery (19 of 22)

58. Host-to-Host Packet Delivery (20 of 22)

59. Host-to-Host Packet Delivery (21 of 22)

60. Host-to-Host Packet Delivery (22 of 22)

61. Default Gateway

62. Routing

63. Routers Routers have the following components: – CPU – Motherboard
– RAM
– ROM
Routers have network adapters to which IP addresses are assigned.
Routers may have the following two kinds of ports:
– Console: For the attachment of a terminal used for management
– Network: Different LAN or WAN media ports
Routers forward packets based upon a routing table

64. Router Functions Lets other routers know about changes
Determines where to forward packets
Translate between different layer2 protocols/interfaces
RouterX# show ip route
D /24 [90/ ] via
R /24 [120/4] via
O /24 [110/229840] via

65. Routing Types
Static/Dynamic
IGP (Interior Gateway Protocol) – RIP, ISIS, OSPF, (E)IGRP
EGP (Exterior Gateway Protocol) - BGP

66. Path Determination

67. Routing Tables

68. Routing Table Entries
Directly connected: Router attaches to this network
Static routing: Entered manually by a system administrator
Dynamic routing: Learned by exchange of routing information
Default route (optional): Statically or dynamically learned; used when no explicit route to network is known

69. Routing Metrics

70. Distance Vector Routing Protocols
Passes periodic copies of routing table to neighbor routes and accumulates distance vectors

71. Link-State Routing Protocols
All routers calculate “shortest paths” using Djikstra algorithm
After initial flood, passes small event-triggered link-state updates to all other routers

72. Routing Protocols
Distance Vector – RIP, IGRP
Link State – OSPF, ISIS
Balanced hybrid - EIGRP

73. Administrative Distance
Route Source
Default Distance
Connected
Static 1
eBGP 20
EIGRP 90
IGRP
100
OSPF
110
ISIS
115
RIP
120
iBGP
200
Unknown*
255
* If the administrative distance is 255, the router does not believe the source of that route and does not install the route in the routing table