aadd day 9 Switch Interfaces

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+---
+id: 08. IPv4 Addressing (Part 2)
+aliases: []
+tags: []
+---
+
+# IPv4 Addressing (Part 2)
+
+## [[IPV4]] address classes
+
+
+| Class |First octet | numeric range| Prefix Length |
+| ----- | ---------- | --------------|    /8        |
+| A     |0xxxxxxxx | 0-127           |    /16       |
+| B     |10xxxxxxx | 128-191         |    /24       |
+| C     |110xxxxxx | 192-223         |              |
+| D     |1110xxxxx | 224-239         |              |
+| E     |1111xxxxx | 240-255         |              |
+
+## Maximum Hosts per Network
+
+Host portion all 0s = Network address (network ID)
+Host portion all 1s = broadcast address 
+
+192.168.1.0/24 -> 192.168.1.255/24
+Host portion = 8 bits = 2^8 = 256
+Maximum hosts per network = 2^8-2 = 254
+
+
+172.16.0.0/16 -> 172.16.255.255/16
+Host portion = 16 bits = 2^16 = 65,536
+Maximum hosts per network = 2^16 -2 = 254
+
+10.0.0.0/8 -> 10.255.255.255/8
+Host portion = 24 bits = 2^24 = 16,777,216
+Maximum hosts per network = 2^24 -2 = 16,777,214
+
+### Formula 
+
+```
+maximum host per network = 2^n-2 
+(n=number of hist bits)
+```
+
+## First/last usable address
+
+192.168.1.*0*/24 ---------> 192.168.1.*255*/24
+00000000                    11111111
+00000001                    11111110
+192.168.1.*1*/24            192.168.1.*254*/24 
+= first usable address      = last usable address
+
+## Cisco router command 
+
+
+### For all the interface info
+
+```Cisco
+R1#show ip interface brief
+
+Interface           IP-address  OK?   Method  Status                Protocol
+GigabitEthernet0/0  Unassigned  YES   unset   adminstratively down  down
+```
+
+- adminstratively down: Interface has been disabled with the shutdown command
+- This is the default Status of Cisco [[router]] interfaces.
+- Cisco switch interfaces are NOT administratively down by default
+- Status = Layer 1 status (is there a cable) 
+- Protocol = Layer 2 status  (is ethernet function conrectly)
+
+
+### enter the configuration mode for the interface
+```Cisco
+// shortcut for configuration terminal
+R1#conf t
+// for configuration of the interface
+R1#interface gigabitethernet 0/0
+//shortcut
+R1#in g0/0
+```
+
+### setting the ip adress
+
+```Cisco
+R1#ip address 10.255.255.254 255.0.0.0
+//enable the interface
+R1#no shutdown
+// view the change
+R1#do show ip interface brief
+// shortcut version
+R1#do sh ip int br
+```
+
+### show interfaces 
+
+to see all the details of the interface
+
+```Cisco
+R1#show interfaces g0/0
+```
+
+### descriptions of an interface
+
+```Cisco
+// see all the description
+R1#show interfaces description
+// for assigning a description 
+// swithc to configuration interface
+R1#int g0/0
+R1# description ## to SW1 ##
+```
+
+## Review
+
+- IPV4 address classes (review clarification)
+- Finding the maximum number of hosts, network address, broadcast address, first usable address,
+  last usable address of a particular network
+- Configuring IP addresses on Cisco device