Trunk Introduction and Configuration
A, Trunk Overview
** What is a Trunk? Why Trunk? ***
First, we need to understand the basis of the VLAN on the assumption that such a situation, when there are multiple network switches, how to communicate it is located between different hosts on the same VLAN switches?
So we are talking about the role of the main trunk is to achieve mutual communication between different hosts of the same VLAN switch
The following first introduce two concepts
Access link: VLAN access terminal PC access data corresponding to only run
Relay link: access to other network devices (switches, routers) can run all VLAN data Trunk
Two, VLAN identification
Ethernet implemented on the relay, there are two types of packages
1.ISL (Cisco proprietary standard)
2.IEEE 802.1q: switch labeled and removed, and the relay link can run the data of all VLAN (not unless they do not allow certain set)
The frame format of the contents of four bytes as follows:
(1) 2-byte tag protocol identifier (the TPID) 0x8100 contains a fixed value, the value of the flag information indicates the frames with 802.1q;
(2) 2-byte Tag Control Information (TCI) contains the following elements:
User priority 3: 802.1q this field is not used
A specification format identifier (CFI): CFI commonly used in Ethernet and Token Ring networks. Ethernet, which is usually set to the value 0
12 VLAN identifier (VLAN ID): This field uniquely identifies a VLAN frame belongs. VLAN ID may uniquely identify 4096 one VLAN, but the VLAN 0 and VLAN 4095 are reserved.
The following experiments used in this type of format is the encapsulation of
Third, the test configuration and verification process
Experiment Environment: GNS3 1.3.10 version of the software, the topology as shown in FIG.
(1) after opening device, on the PC 'ip set, then the test can ping to send a ping packet to PC3 PC4 is possible, there is no problem description
(2) disposed on the two switches;
sw1 configuration: divide and build VLAN trunk link
Sw1 and sw2 disposed on similar:
Attempts to communicate between each other after the completion of the host PC (3)
The result is the same VLAN can communicate with each other between the host, but is unable to communicate between the host between different VLAN. If you are implementing communication between different VLAN hosts need to learn the principles of three-tier exchange, see next blog. thanks for reading!