Analyze and view how Cisco device VTP works and the STP spanning tree principle

Experiment

Topology diagram:

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Note: VTP is divided into three modes (one, server, two, client, three, transparent). At least one server mode per admin domain facilitates creation, deletion, and modification of VLANs. The data frames that the VTP advertises are sent to the multicast address: 01-00-0C-CC-CC-CC, which are the frames that the neighboring devices can receive.

Requirements for VTP:

One, each switch within the domain must be the same VTP domain name. Second, the switch must be contiguous, and the neighboring switch needs the same domain name.

Three, all switches must be configured as trunk links.

Configuration of VTP:

One, determine the VTP version. Second, add to the admin domain, determine its name and password, (configure password in a high-security environment) Three, select a VTP mode for the switch. Four, whether to enable VTP pruning.

Experimental steps:

One, configure SW1 for server mode, other for client mode, switch interface configured as Trunk

SW1:

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SW2:

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SW3:

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Second, configure the VLAN on the server mode switch, the other switches learn the VALN information of the server mode switch, and view it through the show VLAN-SW b command.

SW1:

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To view VLAN information on SW2 and SW3:

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Third, view the VTP configuration changes for the switch by the show VTP status command, add VLANs on the SW1, and view the VTP configuration information for the other switches.

The following are no VLANs added:

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Here is the Add VLAN:

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The above information can be seen in configuration modification number 7: Before the number is 5, stating that two different VTP advertisements were issued, two VLANs added, each switch MD5 summary information update synchronization

Four, for security, configure the VTP password for the server mode switch, add VLAN, view the VALN information of each switch

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The above two switches are not configured with a VTP password all do not learn to VLAN information

View VLAN information for SW2 after configuring a VTP password for the SW2 switch in client mode

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After the SW2 configured with a VTP password, the switch learns the VLAN information after viewing it

VTP Experiment Complete

Here's how the STP spanning tree works:

To build a tree algorithm: One, select the root bridge, two, select the root port, and three, select the specified port.

Spanning tree algorithm definition: When comparing STP parameters, the value is small with high precedence.

One, select the root bridge, (the small MC address is the root bridge) two, select the root port (note: The root port exists on the non-root bridge, when comparing the port ID value, the port ID value of the peer received is compared), select the root bridge in order is: 1, to the root bridge the lowest root path cost, 2, the direct-connected bridge ID is minimal, 3, the port ID is minimal. Three, select the specified port, 1, with the path cost is lower, 2, where the switch bridge ID value is small, 3, the value of the port ID is small (note: the interface on the root bridge is the specified port, because the path cost is 0, compared to the port ID value, compared to the self port ID value)

Through the above principle through the command to view the STP information and analysis of the end which switch blocked which port (based on VLAN 1 view)

SW1:

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SW2:

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SW3:

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The F1/1 interface is blocked by looking at the end of the switch SW3

One: Select the root bridge

By viewing the SW1 as the root bridge for VLAN 1

Two: Select the root port

By looking at the root port on a non-root bridge based on the principle roots, the lowest root path cost to the root bridge is derived directly on the SW2 on the f1/0 and the F1/2 on the SW3 on the root port and the SW2 on the F1/1 as the root port

Three: Select the specified port

By looking at the port ID on the SW2 is small, all for the specified port

The F1/1 interface on the remaining SW3 is blocked port

Experiment completed

Analyze and view how Cisco device VTP works and the STP spanning tree principle