IP address and subnet division (A2)

IP Address

IPV4 --- 32 Bit binary structure --- dotted decimal

IPV6 --- 128 Bit binary structure --- It's hexadecimal

Network bit --- The network bits are the same , It means in the same broadcast domain

Host bit --- In the same broadcast domain , Use the host bit to distinguish different hosts
Subnet mask --- Continuous 1 and 0 form ,1 On behalf of network bit ,0 Represents the host bit

Address type

A、B、C --- Unicast address --- It can be used as a source IP Address , It can also be a goal IP Address

A：255.0.0.0

B：255.255.0.0

C：255.255.255.0

D --- Multicast address --- Only as a target IP Address using , Cannot be used as a source IP Use

E --- Reserved address

A：0XXX   XXXX --- （0~127）1~126

B：10XX   XXXX --- 128~191

C：110X   XXXX --- 192~223

D：1110   XXXX --- 224~239

E：1111   XXXX --- 240~255

unicast --- One to one communication

Multicast --- One to many communication （ The same multicast group ）

radio broadcast --- One to all communication （ All in the broadcast domain ）

stay IP In the address space , Part of it IP The address is called private IP Address （ The private network IP Address ）, The rest is called public IP Address （ Public network IP Address ）--- We habitually use private networks IP The network built by address is called private network , Use the public network IP The network built by address is called public network .---- Private address can be reused , However, uniqueness must be guaranteed within the private network .

A：10.0.0.0 ~ 10.255.255.255 amount to 1 individual A Class segment

B：172.16.0.0 ~ 172.31.255.255 amount to 16 individual B Class segment

C：192.168.0.0 ~192.168.255.255 amount to 256 individual C Class segment

special IP Address

1、127.0.0.1 ~ 127.255:/255.254 --- Loopback address

2、255.255.255.255 --- Restricted broadcast address --- Only as a target IP Use

3、 All the hosts 1----192.168.1.255/24---- Direct address —-- Only as a target IP Address using

4、 All the hosts 0 ---192.168.1.0/24--- Network segment （ network address , network number )

5、0.0.0.0 ---- 1, No, IP Address    2, all IP Address

6、169.254.0.0/16 --- Local link address / Automatic private address

VLSM --- Variable length subnet mask

192.168.1.0/24

192.168.1.0 0000000 --- 192168.1.0/25

192,168.1.1 0000000 --- 192.168.1.128/25

CIDR --- No inter domain routing

Take the same . Go different --- For binary

192.168.00000000.0/24

192.168.00000001.0/24

192.168.00000010.0/24

192.168.00000011.0/24
 

192.16B.0.0/22---- HYPERNET

172.16.0.0/24

172.16.1.0/24

172.16.2.0/24

172.16.3.0/24

172.16.0.0/22---- Summary

Generation conditions of direct route --- 1, Dual interface UP,2, The interface must be configured IP Address

Get unknown route information of network segment

Static routing ： Routing entries manually configured by the network administrator

Dynamic routing ： All routers run the same routing protocol , after , Routers communicate with each other . hand over

The flow calculates the routing information of the unknown network segment

Advantages of static routing --- 1, The choice of route is more reasonable ;2, safer ;3, No additional resources are required

shortcoming --- 1, Large amount of configuration ;2, Static routing cannot automatically converge based on changes in topology

Basic configuration of static routing ：

Method 1 ：[R1]ip route-static 192.168.3.0 24 192.168.2.2 ---- You need to recursively find the interface

Method 2 ：[R1]ip route-static 192.168.3.0 24 GigabitEthernet 0/0/1--- Need to activate generation ARP

[r2-GigabitEthernet0/0/0]arp-proxy enable --- The activation agent ARP ---- ARP A kind of , After activation , The router will check the received ARP Request package , be based on ARP Requested IP Address view local routing table , If the local route can reach , Will pretend to be the other party's IP Address reply ARP The reply . To his own MAC Address reply , after , The data is sent to the router , The router forwards .

Method 3 ：[r1]ip route-static 192.168.3.0 24 GIgabiEthernet 0/0/1 192.168.2.2 --- Recursive lookup is not required

Method four ：[r1]proute-static 192.168.4.024192.168.3.2 --- Write down two jumps , Recursive direct search is required

Extended configuration of static routing ：

1、 Load balancing --- When a router accesses the same target with multiple paths with similar overhead , You can split the volume and go from multiple paths at the same time , Play the effect of superimposing bandwidth

2、 Manual summary --- When a router can access multiple consecutive subnets , If they all pass the same next jump . These network segments can be summarized and calculated , Directly write a static route to the summary network segment . You can reduce the number of routing table entries , Improve forwarding efficiency

3、 Routing black holes --- In summary , If the network segment that does not actually exist in the network is included , It may cause the flow to have no return , Reasonable division and aggregation of wasted link resources can reduce the generation of routing black holes

4、 Default route -- A route that does not limit the destination . When looking up the table , If all routes do not match , The default route will be matched

[r1]ip route-static 0.0.0.0 0 12.0.0.2

5、 Empty interface routing --- Prevent routing black holes and default routes from meeting and leaving the ring . Configure... On the black hole router — Routes that reach the summary network segment and point to the empty interface .

1、NULL 0 --- If the outgoing interface of a route entry points to an empty interface , The datagram matching this route information will be discarded

2、 Matching principle of routing table --- The longest match principle ( The principle of exact match )

[r1]ip route-static 192.168.0.022 NULL 0

6、 Floating static routing --- By modifying the default priority of static routing , Achieve the effect of backup [r2]ip route-statlc 192.168.0.0 22 21.0.0.1 preference 61