Shulou(Shulou.com)06/03 Report--

OSI

Network device management:

Software:

System file

Configuration file

Startup configuration file-startup-config

Running configuration file-running-config

Hardware

Flash- system files

Nvram-startup-config

Ram-running-config (save) (cisco-write)

Management:

Local Management-console

Remote Management-telnet

MAC:

Action

Uniquely identifies a network device globally

Express

Total 48 bit, or 6 bytes

Represented by hexadecimal

Structure:

24 bits on the left, representing the manufacturer's code

The 24 digits on the right represent a device number customized by the manufacturer

Note:

MAC address is a physical address and cannot be changed.

Equivalent to the address of a building in the human world

In the network world, only with the help of IP address and MAC address can a communication device be uniquely identified.

In order to be able to get a MAC address corresponding to an IP address, you need ARP

ARP:address resolution protocol: address Resolution Protocol

Based on an IP address, the corresponding MAC address is resolved.

Layer 2 header (MAC / Ethernet header): a total of 14 bytes Byte destination MAC+ source MAC+ type destination source type 6Byte 6Byte 2Byte layer 2 tail: FCS,frame checksum, frame checksum, total 4Byte function: based on an IP address, resolve the corresponding MAC address in order to achieve a complete encapsulation type of data: static ARP entry: always exists in the ARP table Dynamic ARP entry: exists in the ARP table within the valid time; the ARP valid time for network devices is 4 hours View terminal equipment: arp-a network device: display arp | show ip arp Cisco device: static ARP-arp 192.168.1.254 xxxxxx arpa terminal device: static ARP-arp-s 192.168.1.254 xxxxx Note: the MAC address is all 1, indicating the broadcast MAC address MAC address is all 0, indicating unknown MAC address; principle: 1, source host, send by broadcast, ARP request packet; 2, target host, after receiving ARP request packet, first check whether the destination MAC of layer 2 header is the same as yourself, or whether it is a broadcast address If so, analyze the ARP message behind the layer 2 header: if the "target IP" is the same as yourself, first record the corresponding relationship between the sender's IP and MAC, and put it in your local ARP table. 3. The destination host is returned as unicast, and the ARP responds to the packet. 4. The source host, after receiving the ARP response message, carries out the same data processing as step 2, and forms the ARP table locally. Type: ordinary ARP: resolve the corresponding MAC address based on the IP address; reverse ARP: obtain the corresponding IP address based on the MAC address; agent ARP good faith agent malicious agent

The address requested by gratuitous ARP for no reason ARP:APP is self, which is used to discover and connect with yourself.

Use duplicate IP addresses, that is, IP address conflict detection.

0x0800 IP protocol

0x0806 ARP protocol

418838267@qq.com

Routing:

Definition:

Interworking between different network segments is called routing

Achieve:

"routing" is realized through devices with routing functions.

Such as routers, multilayer switches

Core:

Routing tabl

View the routing table: show ip route

Analyze the routing table:

How a router works:

1. Routes only care about IP addresses, not MAC addresses

2. The router only cares about the destination IP address, not the source IP address.

3. After receiving the data packet, the "target IP" will be proposed.

Match the routing Table entry:

The process is as follows:

# first analyze the subnet mask length of the route entry

# secondly, according to the length of the subnet mask, extract

The bit of the response length in the destination IP address

# again, the bits that will be proposed, with the routing entry

Make a comparison

If the same is the same, match and forward from the corresponding port.

Get out,

If it is different, it means that it does not match, then it is discarded.

Data packet

Route viewing and configuration:

View:

Show ip route

Configuration:

Static route configuration:

(ip config) # ip route 192.168.23.0 255.255.255.0 fas0/0

Ip route 192.168.23.0 255.255.255.0 192.168.12.2

This method is recommended.

Wrong way of thinking:

The third layer is impassable. Look at the route.

Show ip route+ Target IP

1. Master the data forwarding path under normal circumstances

2. Segmented processing

3. In each segment, troubleshooting is based on OSI model and "data forwarding mode".

Debug ip icmp View process

Debug arp process View status (Debug Protocol)

Verify the command:

Show ip interface fas0/0- > status of proxy ARP

Show interface fas0/0- > check the MAC address of the port

Show ip arp-> View the ARP table

DebugARP- > View the working process of ARP on the device

Undebug all-- > turn off all debug commands on the device

Debug ip icmp-- > View the working process of ping

R2:

R2 (config) # interface fas0/0

R2 (config-if) # no ip proxy-arp

Recommendations:

When configuring a static route, the next hop uses the IP address

Display ip routing-table

Ip route-static IP + Mask + next Hop

Terminal debuggingterminal monitor

Huawei static route configuration commands:

System-view

[R1] ip route-static 192.168.3.0 255.255.255.0

192.168.2.1

[R3] ip route-static 192.168.2.0 255.255.255.0 192.168.3.3

Verification and testing:

Display ip routing-table

Ping 192.168.3.3

Ping 192.168.2.1

Open the debug debug command:

Terminal monitor / / enable terminal monitoring function

Terminal debugging / / enable monitoring of debugging

Debugging ip icmp / / enable debugging of icmp

Experimental results:

PC----PC4, ping each other.

192.168.1.1----192.168.4.1

"gateway"

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