360 written tomorrow, specially collected under the network knowledge, cramming.
1 568A 568B line sequence
568A green white green orange white blue orange white brown brown white
568B orange white orange blue green white green white brown white Brown (formerly of the University are used in this)
2 data access speed sorting
CPU-> Memory -> Hard Disk -> Disk
3 commonly used network ports
UDP: DNS(53) TFTP(69) SNMP(161)
TCP: SMTP(25) TELNET(23) HTTP(80) FTP(20 21)
4 IOS 7-layer protocol model : Physical layer - Data Link Layer - Network Layer - Transport Layer - Session Layer - that layer - the application layer
Four TCPIP protocol model : Physical layer - Data Link Layer - Network Layer - Transport Layer - Application Layer
5 computer how many ports
TCP 65535 UDP 65535 131072 total
6 cache and buffer the difference?
cache buffer is composed of hardware; Buffer is the buffer, software implemented by a RAM.
7 dynamic routing and static routing
Dynamic routing protocols Type:
(1) RIP routing protocol
RIP protocol was originally developed for Xerox Xerox parc common protocol network system design, and is commonly used in Internet routing protocols. RIP uses distance vector algorithm, i.e. the distance according to the router routing, it is also known as distance vector protocol. Routers to collect all the different paths to reach the destination, and the path to save the information on the site to reach the minimum number of each destination, in addition to the best path to reach the destination, no other information are to be discarded. While the router also notifies the collected routing information with other routers adjacent to the RIP. In this way, the correct routing information gradually spread to the entire network.
RIP is widely used, it is simple, reliable, easy to configure. But RIP is only applicable for small homogeneous networks, because it allows the maximum number of stations is 15, a destination any more than 15 sites were marked as unreachable. And RIP routing information once every 30s radio also broadcast storm caused a major reason for the network.
(2) OSPF routing protocol
0SPF is a link-state routing protocol, each router needs to send to all the other routers in the same management domain link state advertisement information . Including information about all interfaces, all the measurements and other variables in the OSPF link state advertisement. 0SPF using the router must first collect information regarding the link status, and calculate the shortest path to each node according to a certain algorithm . The routing protocol based on distance vector routing updates sent only to its neighboring routers.
Unlike RIP, OSPF will be an autonomous domain is subdivided into regions, i.e. correspondingly there are two types of routing method: when the source and destination in the same area, using the routing area; when a different source and destination areas , the routing section is used. This greatly reduces network overhead and increase network stability. When a router in one zone out of the failure does not affect the normal operation of other routers in the autonomous region domain, it also gives network management, maintenance convenience.
(3) BGP routing protocol BGP4 and
BGP is an external gateway protocol is TCP / IP Internet designed for among multiple ASs. It is not based on pure link state algorithm, nor is it purely based on the distance vector algorithm. Its main function is to exchange network reachability information with other BGP autonomous domains. Each autonomous domain can run different internal gateway protocol. BGP update information includes a network number of pair information / autonomous domain path. Autonomous arrival path comprises autonomous string subject to a specific network, which updates the information transmitted via the TCP, in order to ensure the reliability of transmission.
In order to meet the growing needs of Internet, BGP is constantly evolving. In the latest BGP4, a similar route can also be combined into one route.
(4) IGRP and EIGRP protocols
IGRP and EIGRP protocols are early invention by Cisco, a dynamic routing protocol based on distance vector algorithm. EIGRP (Enhanced Interior Gateway Routing Protocol) is an enhanced version of IGRP protocol. It is the dynamic Interior Gateway Routing Protocol, still using the vector - distance algorithm. But its implementation has been a great improvement over IGRP, its convergence properties and operating efficiency than IGRP have improved significantly.
Its astringent properties is based on DUAL (Distributed Update Algorithm) algorithm. DUAL algorithm makes it impossible to form a loop path in the route calculation. Its convergence time can rival those of any other routing protocols that already exists.
The main difference between Enhanced IGRP and other routing protocols include: wide convergence speed (Fast Convergence), to support variable length subnet mask (Subnet Mask), and local updating multiple network layer protocols. Enhanced IGRP storage router performs all of its neighboring routing table to select the path using various rapid (Alternate Routes) in it. Without the right path, Enhanced IGRP queries its neighbors to obtain the desired path. Until you find the right path, Enhanced IGRP queries will be terminated, otherwise continue.
EIGRP EIGRP routing protocol for all the arbitrary mask length of route aggregation, thereby reducing the routing information transmission, saving bandwidth. Further EIGRP protocol can be arranged on any bit boundary router interface support route aggregation.
EIGRP does not make periodic updates. Instead, when the path metric change, Enhanced IGRP send only partial update (Partial Updates) information. Local automatically update information transmission is limited, so that only those routers require the information to be updated. Based on the above two properties, thus Enhanced IGRP bandwidth much less than the loss IGRP.
Use Enhanced Interior Gateway Routing Protocol, a router to maintain a routing table a copy of its neighboring routers. If it can not find these tables from a route to reach the destination, it asks a route to its neighboring routers and they in turn ask their adjacent router until it finds a route. Note that in order to maintain the state of all routers in the neighboring routers, each router issuing timing of a "handshake" packets. You did not receive a "handshake" in a certain time interval the router packet is considered invalid.
Static routing refers to a routing table route manually set by the network administrator. The benefits of static routing is that network addressing fast for the network was little changed network system.
Dynamic routing means the routing table is not set manually by the network administrator, but rather address learning mode to automatically generate a routing table by the router through the port. The benefits of dynamic routing is strong adaptability to changes in the network, the network environment suitable for large changes in the network system.
In a router, you can also configure one or more static routes and dynamic routing. They maintain their routing tables are provided to the forwarding process, but between these routing table entries may conflict. This conflict can be resolved by configuring the priority of each routing table. Generally, static routes with the highest default priority, when other routing table entry with its contradictions, are by static routing and forwarding.
8 commonly used backup
Full backup, differential backup, incremental backup
1, full backup (Full Backup)
Backup all selected folder does not depend on the archive attribute of the file to determine the backup those files. During the backup process, any existing marks are cleared, each file is marked as backup. In other words, clear the archive attribute.
Refers to a full backup is a complete copy of all data or applications on a certain point of time. In practice the tape is to use a full backup of the entire system, including all system and data therein. The greatest advantage of this backup is to just use a tape, you can recover lost data. Thus greatly speeding up the recovery time of the system or data. However, its disadvantage in that the large number of duplicate information backup data of the respective full backup tape; Further, since the amount of data to be backed up every time a considerable, so the backup time was needed.
2, differential backup (Differential Backup)
There are changes in the data after the backup since the last full backup. Differential backup, backup only those labeled selected files and folders. It is not clear the mark, is not marked as a backup file that is backed up. In other words, the archive attribute is not cleared.
A differential backup refers to this period of time after a full backup to perform a differential backup, backup to add or modify those files. During recovery, we need to first full backup and the last differential backup to restore. Differential backup backup strategy to avoid the other two defects, also have their own advantages. First, it has an incremental backup time is short, save disk space advantage; secondly, it has a full tape backup and recovery less necessary, recovery time is short features. The system administrator only needs two tapes, that the previous day's differential backup tape full backup tapes and disaster, you can restore your system.
3, incremental backup (Incremental Backup)
After the data has changed since the last backup backup (including full backup, differential backup, incremental backup). Incremental backup, only backup of marked files and folders selected, it clears the mark, either: after the tag file backup, in other words, clear the archive attribute.
Incremental backup is a full backup after on or incremental backup, each subsequent backup only back up files and who increase compared with the previous modified. This means that the object is first incremental backup is to increase and modify the generated full backup file; the second incremental backup target is to increase and modify After the first incremental backup generated files, and so on. The most significant advantage of this backup method is: no duplicate backup data, the amount of data is not backed up, the backup time required is short. But incremental backup data recovery is more troublesome. You must have the last full backup and all incremental backup tapes (if lost or damaged one of a tape, it will cause failure recovery), and they must be individually along the anti-chronological order from the full backup to an incremental backup push recovery, so this greatly extends the recovery time.
Commonly used types of summary database backup
backup database is compulsory site managers, then the common database backup, what does? How to choose?
There are four types of database backups were used in different occasions, a brief overview below.
1, full backup
This is the most common way, it can back up the entire database, containing all the database objects user tables, system tables, indexes, views, and stored procedures. But it takes more time and space, it is generally recommended done once a week a full backup.
2, transaction log backup
The transaction log is a separate file that records changes to the database, when only need to copy the backup since the last change made to the database since the backup, so only very little time. In order to make the database is robust, even more frequently recommended hourly transaction log backup.
3, differential backup
Also called an incremental backup. It is another way to back up only a part of the database, it does not use a transaction log, instead, it uses a new image of the entire database. It is smaller than the initial full backup, since it is only since the last full backup of the database changes. The advantage is that storage and fast recovery. Recommended to do a differential backup every day.
4, file backup
Database can consist of many files on your hard disk. If the database is very large, and one night not able to complete its backup, then part of the file backup nightly backup of the database can be used. As the general database is not large enough to have to use more than one file storage, so this backup is not very common.
9 different switches and hubs?
From the work point of view, the hub is a broadcast mode, which means that when a working port hub ports have all the other names to listen to information, easy to produce broadcast storms. When the larger network when the network performance will be greatly affected, then the method used this phenomenon to avoid it? Switch can play this role, when the exchange-of-phase response between each other only when issuing requests and destination ports without affecting other ports, the switch can isolate collision domains and effectively suppress generation of the broadcast storm.
From the bandwidth point of view, no matter how many ports the hub, all ports are sharing a bandwidth at the same time there are only two ports to transmit data, the other port can only wait; while the hub can only work in half-duplex mode. And for the switch, each port has a monopoly of bandwidth when the two ports does not affect the work of other ports, while the switch can not only work in half-duplex mode can operate in full-duplex mode .
10 IGP and EGP is different
IGP: 内部网关协议（Interior Gateway Protocol）
内部网关协议（IGP）是一种专用于一个自治网络系统（比如：某个当地社区范围内的一个自治网络系统）中网关间交换数据流转通道信息的协议。网络IP协议或者其他的网络协议常常通过这些通道信息来决断怎样传送数据流。目前最常用的两种内部网关协议分别是：路由信息协议（RIP）和最短路径优先路由协议（OSPF）。
EGP：外部网关协议（Exterior Gateway Protocol）
外部网关协议（EGP）是一种在自治系统的相邻两个网关主机间交换路由信息的协议。 EGP 通常用于在因特网主机间交换路由表信息。它是一个轮询协议，利用 Hello 和 I-Heard-You 消息的转换，能让每个网关控制和接收网络可达性信息的速率，允许每个系统控制它自己的开销，同时发出命令请求更新响应。路由表包含一组已知路由器及这些路由器的可达地址以及路径开销，从而可以选择最佳路由。每个路由器每间隔 120 秒或 480 秒会访问其邻居一次，邻居通过发送完整的路由表以示响应。
Reproduced in: https: //my.oschina.net/u/204616/blog/545275