Hcia-r & s self use notes (23) DHCP

DHCP（7/26,64min）

DHCP：Dynamic Host Configure Protocol, Dynamic Host Configuration Protocol

UDP encapsulation , The server is 67, The client is 68

dynamic analysis TCP/IP Information （IP Address 、 Subnet mask 、 The default gateway 、DNS The server etc. ）

The information to be removed from the allocation is lease （ Default one day ,86400s）

ipconfig /all You can see the beginning and end of the lease

In general ,DHCP The server is on the gateway （ not always ）

DHCP System composition ：

DHCP Client（ client ）	Need to get... Dynamically IP Address of the host
DHCP Server（ The server ）	Can provide DHCP Function of the server or network device
DHCP Relay（ relay ）	Generally, it is network equipment such as router or layer 3 switch

  The topology is as follows ：

SW1：

<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]un in en
Info: Information center is disabled.
[Huawei]vlan batch 10 20
Info: This operation may take a few seconds. Please wait for a moment...done.
[Huawei]int gi0/0/1
[Huawei-GigabitEthernet0/0/1]p l t
[Huawei-GigabitEthernet0/0/1]p t a vlan all
[Huawei-GigabitEthernet0/0/1]qu
[Huawei]int gi0/0/2
[Huawei-GigabitEthernet0/0/2]p l a
[Huawei-GigabitEthernet0/0/2]p d v 10
[Huawei-GigabitEthernet0/0/2]qu
[Huawei]int gi0/0/3
[Huawei-GigabitEthernet0/0/3]p l a
[Huawei-GigabitEthernet0/0/3]p d v 20

SW2：

<Huawei>sys
Enter system view, return user view with Ctrl+Z.
[Huawei]un in en
Info: Information center is disabled.
[Huawei]sys SW2
[SW2]vlan batch 10 20
Info: This operation may take a few seconds. Please wait for a moment...done.
[SW2]int vlan 10
[SW2-Vlanif10]ip add 192.168.10.254 24
[SW2-Vlanif10]qu
[SW2]int vlanif 20
[SW2-Vlanif20]ip add 192.168.20.254 24
[SW2-Vlanif20]qu
[SW2]int gi0/0/1
[SW2-GigabitEthernet0/0/1]p l t
[SW2-GigabitEthernet0/0/1]p t a vlan all
[SW2-GigabitEthernet0/0/1]qu

stay PC1 Capture packets at the interface , Be careful ,PC1、PC2 No address is configured , At this time will be PC1 The address acquisition method of is changed to “DHCP”

as follows , Grab the PC Of DHCP Discovery message （Discover）

DHCP Simple configuration

SW2：

[SW2]dhcp enable
Info: The operation may take a few seconds. Please wait for a moment.done.
[SW2]int vlanif 10
[SW2-Vlanif10]dhcp select interface 
[SW2-Vlanif10]qu
[SW2]int vlanif 20
[SW2-Vlanif20]dhcp select interface 

here PC1、2 Can get the address , Gateway is Vlanif Address

DHCP Data packets

Common for the first four , The address has been rented out , But there are other hosts that want this address to pass ipconfig /release You can grab DHCP RELEASE package

Discover

I want something （ Mask 、 gateway ……）

Offer

What can I give you

There are two kinds left

why Request It's also a radio ？

Because there may be multiple DHCP The server , You may receive more than one after the broadcast DHCP Server's Offer, The host gets the first Offer

Request Radio represents me only from multiple Offer Choose one of them

DHCP Lease term

Be careful , The Request For unicast （ Ask the landlord to renew the lease ）;

The access switch port corresponding to the host is not set with a fast port （Portfast） Or edge port （Edged-Port） Words , The host at the bottom needs to wait stp convergence 30s（discarding To forwarding）

if 50% when , The server did not respond , be 87.5% Then broadcast （ In a hurry ）

Didn't rent a house （ Sleeping Street ）169.254.x.x

Automatic retention IP

APIPA（Automatic Private IP Addressing）

Window The client cannot access the DHCP Server When renting an address , Automatically use the network number as 169.254.0.0/16 Private address of , Only for those in the same situation PC Temporary communications

DHCP I'm sorry ： Manually configure the address and ping DHCP The server , Check connectivity

Win Medium DHCP Client It also needs to be turned on （ If it does not start , Won't grab Discover package ）

Lease term setting suggestions

Set short ： Increase the network burden , It is suitable for many clients （ Mobile places , Such as airport 、 Station 、 The mall ）

The setting is longer ： Lighten the burden of the Internet （ Fixed place , Such as family 、 Enterprises ）

The server only takes back the address after the lease expires , No matter whether the other party turns on ,

Windows The last rented address will be recorded , After the lease term discover There will be requested ip（ That is, the last address ）, If the environment is changed at this time （ From the company to home ）, Then the other party （ The other dhcp The server ） Will refuse the request , At this point DHCP NAK Data packets

IP Address release

Or the customer takes the initiative to release ,ipconfig /release（Windows）, At this time DHCP Server send out Release message

Or passively release , The server didn't respond before the lease expired , Or the shutdown time exceeds the lease term

 DHCP Address pool

DHCP To configure

dhcp enable	Global on DHCP function
dhcp select interface	Associate interfaces with interface address pools （ The gateway is the interface address ）
dhcp server dns-list x.x.x.x	Configure the interface address pool DNS The server （ You can configure multiple ）
dhcp server lease Numbers	Configure interface address pool lease , default 1 God
dhcp server excluded-ip-address x.x.x.x	Configure the excluded address range of the interface address pool
dhcp select global	Associate interfaces and global address pools （ The interface address is not a gateway , Such as VRRP、DHCP-Relay scene ）
ip pool name	Create a global address pool and name
network x.x.x.x	Configure the assignable network segment address of the global address pool
gateway-list x.x.x.x	Configure the gateway of the global address pool
dns-list x.x.x.x	Configure the configuration of the global address pool DNS Address （ You can configure multiple ）
lease Numbers	Configure the lease term under the global address pool , default 1 God
excluded-ip-address x.x.x.x	Configure the discharge address range under the global address pool
display ip pool [interface gi0/0/x all]	View the properties of the address pool

Wireless router's DNS You can be yourself （192.168.1.1） Help forward domain name resolution to operators

The spanning tree has a small chapter to fill , I feel dizzy , Your mother