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Hcip third day notes

2022-07-16 08:53:00 【Alone 631】

Day 3：

Network type --- It is more divided by the protocol used in the data link layer

MA— Multipoint access network

BMA— Broadcast multipoint access network

NBMA— Non broadcast multipoint access network

P2P— Point to point network

Ethernet protocol --- Need to use MAC Address distinguishes and identifies different host devices .--- Why Ethernet needs to be used MAC Address for data addressing , This is mainly because the layer-2 network using Ethernet components can contain multiple （ Two or more ) The interface of , Each Ethernet interface can carry out layer-2 communication by means of interactive Ethernet frames .----BMA

When a network can only contain two devices , Then such a network does not need MAC Address address , Such a network is called P2P.

T1---1.544Mbps

E1---2.048Mbps

Ethernet — Frequency division technology — So called frequency division , It is to send radio waves of different frequency bands on the same transmission medium at the same time , And they don't interfere with each other , Realize the parallel transmission of data .

1.HDLC--- Advanced data link control protocol — Compatibility is poor

The standard HDLC： Yes ISO Those that meet industrial standards issued by the organization HDLC edition .

Nonstandard HDLC： Major manufacturers based on Standards HDLC The agreement has been improved .（ Standard and non-standard may be incompatible ）

（ By default , The encapsulation protocol used in the serial network of Cisco device components is HDLC, Huawei uses... By default PPP agreement ）

【r1】display interface Serial 4/0/0--- View the layer 2 features of the interface

【r1-Serial4/0/0】link-protocol hdlc --- Modify the protocol type of layer 2

PPP-- Point to point agreement

PPP— Point to point agreement

Strong compatibility and unified version , And as long as it supports full duplex serial lines , You can use PPP Protocol encapsulation .
PPP The protocol has strong portability .---PPPoE
Support authentication and authorization

PPP And TCP be similar , Before transmitting data , Need to establish PPP Conversation .

Link establishment phase ---LCP establish
Authentication phase — optional
Network layer protocol negotiation stage ---NCP negotiation ---NCP An agreement is a collection of agreements .--IPCP agreement

PPP The agreement has a series of member agreements —LCP（ Link control protocol ）= An agreement

--NCP( Network control protocol == A bunch of agreements )、

etc.

F--Flag---0111110

A…-Address---1111111

C---control---00000011

agreement --- Indicates the protocol type used by the upper layer .

FCS--- Frame check sequence --- Ensure data integrity

Link establishment phase —LCP establish

Content of negotiation :

1.MRU： Limit PPP The maximum number of bytes carried by the data part of the frame ---1500 byte

2. Negotiate whether to establish certification in the second stage , And choose which authentication to send .

2. Authentication phase — optional ---PPP Generally by calling aaa Platform to complete the certification process — Sure .

PPP Can be one-way authentication , You can also have two-way authentication

PAP— Password authentication protocol — The authenticated party sends the password and user name to the authenticator in clear text , If the certification results, the certification party will reply ACK, Then reply NAK.（ unsafe ）

CHAP- Challenge the handshake agreement --- safer , No longer send plaintext directly for authentication , Instead, authentication is performed by comparing the summary values .

HASH（ Hash function — In the calculation summary ）-- Convert input of any length into output of any length .-- Not encryption

Same input , Same output .
Irreversibility
Avalanche effect ： A slight change will make a big difference

MD5—HASH One of the algorithms , Input of any length can be converted into 128 The output of a

3. Network layer protocol negotiation stage —NCP agreement — If the third floor uses IP agreement , You need to use IPCP Protocol to negotiate its parameters

1.IP Compression format of message ;

2.IP Address