** ICMP protocol:
Function: troubleshoot network problems, ping is the use of ICMP protocol, Tracert
principle: sending ICMP packets, routing node receives a reply later
** eNSP
ARP protocol: Get Mac addresses already know the IP address of the destination of the
ARP request: by send broadcast in the LAN, the device will send all broadcast domain, not across a router, Mac address different segments, resolve network of
VRP: operating system developed by Huawei on the Huawei routers, switches, firewalls, AP, gateway system provides
version: VRP5 , VRP8 with up
switch: data link layer, physical layer (there are three switches, routers equivalent)
router: data link layer, physical layer, network layer
broadcast domains: the network-wide broadcast transmission, typically by a division boundary router
= ================================================== =========================
example: mail transport
mail sent from a computer inside, through the application layer (written content | compression, encryption, encoding | session , TCP three-way handshake ah),
a transport layer, into TCP | UDP header and the port, the corresponding firewall can block
and even after data Layer, the Mac address into the source process to the data frame transmitted by the card, by a twisted pair transmission reaches the switch (physical layer)
after reaching the switch, unpack the data frame, locate the Mac address of the destination host through the IP ARP, if present, LAN traffic is sent directly,
To reach the target host, the decompressed data frames -> transport layer firewall filtering, passed to the application listening port, -> Application Layer (decompresses, decodes, decrypts) -> display
and if not, to the gateway, the gateway Mac address sent by reaches the public network is
a router with NAT protocol, replaces the original IP public network IP, a by-hop IP routing table is found, obtain the Mac address routing startle, and replace the original target Mac Mac, re-encapsulating the data frame
if the destination IP absent, lost directly
sent to the next router
statement:
transport layer: breaking network layer: packet data link layer: physical layer data frame: bit
================== ========== essence =================================
IP V4 a total of 4.3 billion a, IPV6 Earth per one square meter can be assigned 1564,
IP addresses are divided into categories ABCDE, IPv4 there is also a private address, agreed to divide IP network
requirements: a company that has four departments, each department requires different segment, a department of not less than 50 hosts
192.168.1.100 11000000.10101000.00000001.01100100 gateway
255.255.255.192 11111111.111111 11.11111111.11000000 subnet mask
segments: 4
each network host: 2 ^ 6-2 = 62
11000000.10101000.00000001.00000000 - 11000000.10101000.00000001.00111111 192.168.1.0 (the network address) - 192.168.1.63 (broadcast address)
11000000.10101000.00000001.01000000 - 11000000.10101000.00000001.01111111 192.168.1.64 - 192.168.1.127
11000000.10101000.00000001.10000000 - 11000000.10101000.00000001.10111111 192.168.1.128 - 192.168.1.191
11000000.10101000.00000001.11000000 - 11000000.10101000.00000001.11111111 192.168.1.192 - 192.168.1.255
the IP network address = & subnet mask
the same network address, located in the same segment of
the binary decimal conversion: 8421 method
decimal binary conversion: method make up
171 = 128 + 0 (64) + 32 + 0 (16) + 8 + 0 (4) + 2 + 1 = 10101011
10101011 = 128 + 0 (64) + 32 + 0 (16) + 8 + 0 (4) + 2 + 1 = 171
============================ essence ==================== =============
