Wireless Networking (Wi-Fi); Network Address Translation (NAT); Routing and Routing Protocols

Wireless Networking (Wi-Fi)

IEEE 802.11 Standards

Standard	Frequency	Max Speed	Range	Notes
802.11b	2.4 GHz	11 Mbps	~35m	Old standard
802.11g	2.4 GHz	54 Mbps	~35m	Common in early 2000s
802.11n (Wi-Fi 4)	2.4/5 GHz	600 Mbps	~70m	MIMO introduced
802.11ac (Wi-Fi 5)	5 GHz	3.5 Gbps	~35m	MU-MIMO
802.11ax (Wi-Fi 6)	2.4/5/6 GHz	9.6 Gbps	~35m	OFDMA, better in dense areas
Wi-Fi 6E	6 GHz only	9.6 Gbps	Lower	Less interference
Wi-Fi 7 (802.11be)	2.4/5/6 GHz	46 Gbps	~30m	MLO (multi-link operation)

Wireless Security Standards

Standard	Description	Status
WEP	Wired Equivalent Privacy	Broken — do not use
WPA	Wi-Fi Protected Access	Deprecated
WPA2	Uses AES encryption	Still common
WPA3	Enhanced security, SAE handshake	Current standard

2.4 GHz vs 5 GHz

Feature	2.4 GHz	5 GHz
Range	Longer	Shorter
Speed	Slower	Faster
Interference	More (Bluetooth, microwave)	Less
Penetration	Better through walls	Worse through walls
Channels	14 (3 non-overlapping)	25 (all non-overlapping)

Network Address Translation (NAT)

Why NAT?

The number of IPv4 addresses is limited (about 4.3 billion). NAT allows many devices to share one public IP address.

Types of NAT

Type	Description	Use Case
Static NAT	One private IP ↔ one public IP	Servers with fixed public address
Dynamic NAT	Pool of public IPs assigned dynamically	Limited public IP pool
PAT (Port Address Translation)	Many private IPs share one public IP using different ports	Home routers, office

PAT (NAPT) — Most Common

Private IP:Port    → NAT Table →    Public IP:Port
192.168.1.100:12345 → 203.0.113.1:40001 → Internet
192.168.1.101:54321 → 203.0.113.1:40002 → Internet
192.168.1.102:9876  → 203.0.113.1:40003 → Internet

Routing and Routing Protocols

What is Routing?

Routing is the process of finding the best path for data to travel from source to destination across networks.

The Router:

Maintains a routing table with network paths
Selects best path based on metrics (hop count, cost, bandwidth)
Forwards packets from one network to another

Types of Routing

Type	Description	Configuration
Static Routing	Routes manually configured by admin	Manual
Dynamic Routing	Routes learned automatically via routing protocols	Automatic
Default Routing	Single route "gateway of last resort"	Manual

Routing Protocols

Interior Gateway Protocols (IGP) — within one organization

Protocol	Type	Algorithm	Metric
RIP (v1, v2)	Distance Vector	Bellman-Ford	Hop count (max 15)
OSPF	Link State	Dijkstra's SPF	Cost (bandwidth)
EIGRP	Hybrid	DUAL	Bandwidth, delay, load, reliability
IS-IS	Link State	Dijkstra's SPF	Cost

Exterior Gateway Protocols (EGP) — between organizations/ISPs

Protocol	Type	Use
BGP (Border Gateway Protocol)	Path Vector	Internet routing between ISPs

Routing Table Example

Network          Next Hop         Interface    Metric
192.168.1.0/24   directly         eth0         0
10.0.0.0/8       192.168.1.1     eth0         10
172.16.0.0/12    192.168.1.1     eth0         20
0.0.0.0/0        192.168.1.1     eth0         100   ← default route