Link Integrity Server Table

The Link Integrity Server Table displays the following details of all the pre-configured server(s):

Parameter Description

Status Specifies the status of the link integrity feature on the device.

By default, it is disabled. To enable, select Enable from the drop down menu.

Polling Time Specifies the time interval, during which the device will check the link integrity with its configured server(s) by sending the ICMP echo probes.

By default, the Polling Time taken is 30 seconds. To configure, enter the time interval between 5 seconds - 180 seconds.

Offline Polling Time Specifies the time interval, during which the device will send the ICMP echo probes to server(s) in offline mode (When the Link status is DOWN).

By default the Offline Polling Time taken is 1 second. To configure, enter the time interval between 1 second - 5 seconds

Polling Retries Specifies the number of attempts made by the device in sending the ICMP echo probes to the server(s), before declaring the overall link status as DOWN.

By default, the Polling Retries taken is 2. To configure, enter the number of attempts between 1-10

Link Status Specifies the connectivity status between a server and a device. Link Status can either be UP, DOWN or NONE.

– UP: Specifies the status of the link when AP device receives the server’s acknowledgment.

– DOWN: Specifies the status of the link when AP device does not receive the server’s acknowledgment.

– NONE: Specifies the status of the link when the AP device is trying to connect to the server(s), that is when the Link Status is neither UP nor DOWN.

Parameter Description

Server IP Address Specifies the IP Address of the configured server. Comment Specifies the user comment on the configured server.

Entry Status Specifies the entry status of the server. By default, it is disabled. To configure, set the entry status as Enable/Disable/Delete from the drop down menu.

– Enable: Enables the server added. – Disable: Disables the server added. – Delete: Deletes the server added.

Link Integrity Table - Add Row

To enable link integrity on the AP device, atleast one entry should be added to the Link Integrity Server Configuration Table. To add an entry, do the following:

1. Click Add in the link integrity screen, theLink Integrity Table - Add Row screen appears:

Figure 5-5 Link Integrity Table - Add Row

2. Configure all the parameters and click Add,to save the added entry.

:

• A maximum of five servers can be added.

• Atleast one server should be added to the table, to enable the link integrity feature on the device.

5.2.3 Spanning Tree Protocol (STP)

The Spanning Tree Protocol (STP) helps to avoid bridged loops in a wireless network and ensures a loop-free topology for bridged LAN (connected on both Wireless and Ethernet interface). Following is the step-by-step procedure on how STP feature works:

a. Disable: In this state, STP is disabled and no traffic is allowed through Wireless and Ethernet interfaces of the bridged LAN.

b. Listening: When STP is enabled, the AP devices exchange Bridge Protocol Data Unit (BPDU) packets in listening state. These BPDU packets contain Bridge Priority and MAC Address information, based on which a Root bridge and Designated Bridge are selected.

• Root Bridge: It is the device that has the lowest MAC Address or highest priority. Based on a Root Bridge,the shortest low cost path is selected and alternate high cost paths are blocked, therefore avoiding loops on the network. Root Bridge transmits the network topology information continuously to other bridges on the network.

• Designated Bridge: It is the device closest to the Root Bridge and is responsible for forwarding the data towards the root port of the root bridge. Designated Bridge determines the shortest low cost path to the destination, via root port. All the other devices in the network other than Root Bridge, act as Designated Bridge.

c. Learning: Once the Root Bridge and Designated Bridge are selected, all the devices learn and update the Bridge Priority and MAC address information in their learn table. Designated Bridge determines the shortest low cost path to via root port, to forward the packets to the destination.

d. Blocking: After selecting the low cost path, the device blocks and disables all the other high cost paths active on other interfaces. Once the path is blocked, no traffic is allowed via that high cost path.

e. Forwarding: The device easily forwards the data packet to the destination via single low cost path selected, with zero loops and interference on the bridged network.

: The state of the port must change from blocking state to listening and learning state, before it can change to the forwarding state.

Example: Let us consider a network with three Bridges (Bridge 1, Bridge 2 and Bridge 3)

Figure 5-6 STP Topology

• Bridge 1 and Bridge 2 are connected via both Wireless and Ethernet interface, while Bridge 3 is connected to Bridge 1 and Bridge 2 only via Wireless interface.

• To avoid a network loop between Bridge 1 and Bridge 2, the STP feature should be enabled on all the devices. • Once the STP feature is enabled, Bridge 1, Bridge 2 and Bridge 3 change from Disable state to Listening stateand

start exchanging the BPDU packets. Bridge 3, having the highest priority and smallest MAC Address, acts as the Root Bridge, and Bridge 1 and Bridge 2 act as Designated Bridges.

• The Designated Bridges (Bridge 1 and Bridge 2) then determine the shortest low cost path via root port, to forward the data from bridge 1 to bridge 2, on a loop- free bridged network.

• Bridge 1 and Bridge 2 switch from Listening state to Learning statewhere they update the learn tables and enable the shortest low cost path determined.

• The STP enabled Bridge 2 then changes from Learning state to Blocking state and blocks all the longest high cost paths, near both wireless and ethernet interfaces.

• Bridge 1 finally changes from Learning stateto Forwarding state and forwards the data packet to Bridge 2 through the shortest low cost path (via the root port of Bridge 3) enabled, avoiding loops on the network.

Figure 5-7 STP Configuration

Tabulated below are ‘STP’ parameters and the method to configure the configurable parameters:

Parameter Description

Status Specifies the status of the STP feature on the AP device.

By default, STP is disabled. To enable, select Enable from the drop down menu.

Bridge Priority Specifies the priority assigned to a bridge.

By default, a bridge is assigned with a priority of 4096. To configure, enter a value between 0 - 61440 (as multiples of 4096).

: Bridge assigned with the lowest value gets the highest priority, and is selected as Root Bridge.

Maximum Age Specifies the maximum time period for an AP device to hold the BPDU packet before discarding it.

By default, it is 20 seconds. To configure, enter the Maximum Age between 6 seconds - 40 seconds.

Hello Time Specifies the time interval in which the Root Bridge sends the BPDU packets periodically. By default, it is 2 seconds. To configure, enter the Hello Time between 1 second - 10 seconds.

Forward Delay Specifies the time interval, for the bridge to be in Learning state and Listening state. By default, it is 15 seconds. To configure, enter the Forward Delay time between 4 seconds - 30 seconds.

:Forward Delay depends on the Maximum Age.

VAP Name Specifies the name of the VAP enabled with the STP feature.

Port State Specifies the state of the port, in which the AP device with STP feature is currently functioning. Port State varies between Disabled, Listening, Learning, Blocking and

Forwarding.

Port Priority Specifies the priority assigned to a port, to participate in the STP process and act as a Root Port (port maintaining connectivity with root bridge, on the interface of an AP device). When the AP device experiences a tie in determining the low cost path towards root, it uses the Port Priority value as a tiebreaker.

By default, Port Priority taken is 16. To configure, enter the a value in the range of 0 - 48 (as multiples of 16).

: The state of the root port is always in Forwarding state.

Port Path Cost Specifies the cost of the path. Path cost is a pre-determined value of the IEEE 802.11 standards, based on the bandwidth and speed on that path. The port with the lowest path cost to the root bridge becomes the root port, gaining high priority.

Click OK and COMMIT, to save the configured parameters.

5.3 Ethernet

This feature enables you to view and configure the speed and transmission mode of the ethernet interface. Navigate to

CONFIGURATION > Ethernet. The Ethernet Interface Properties screen appears.

Figure 5-8 Ethernet Interface Properties

Tabulated below are ‘Ethernet Interface’ parameters and the method to configure the configurable parameters:

Click OK and COMMIT, to save the configured parameters. Entry Status Specifies the status of the selected port.

By default, the Entry Status is disabled. To enable, select Enable from the drop down menu.

Parameter Description

MAC Address Specifies the MAC address of the ethernet Interface.

Operational Speed Specifies the current operational speed of the ethernet interface.

Operational TxMode Specifies the current operational mode of transmission over the ethernet interface. There are two types of transmission modes:

– Half Duplex: Allows one-way transmission at a time; where only receive or transmit operation can be performed at once.

– Full Duplex: Allows two-way transmission, where both receive and transmit operations can be performed simultaneously.

Speed and TxMode Specifies the speed and transmission mode of the ethernet interface. By default, the AP device is in Auto mode, which means that the AP device negotiates with its switch or hub to automatically select the highest throughput option supported by both sides. To configure, select the Speed and TxMode from the drop down menu.

:

• ‘Speed and TxMode’ is configurable only for AP-8100.

• Ensure that the same ‘Speed and TxMode’ is configured at both the ends of a wireless link.