Bridge Test

Bridging is a technique used by the NetScaler appliance for forwarding packets between network interfaces in the VLANs configured on it. Layer 2 traffic is bridged within a port-based VLAN. By observing the movement of the bridged packets over time, administrators can understand the load on the appliance, and be proactively alerted to issues such as bridge loops and packet collisions. The Bridge Test enables administrators to do just that.

Target of the test : A NetScaler VPX/MPX

Agent deploying the test : A remote agent

Outputs of the test : One set of results for the NetScaler appliance being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The IP address of the host for which the test is being configured.

NetScaler Username and NetScaler Password

To monitor a NetScaler device, the eG agent should be configured with the credentials of a user with read-only privileges to the target NetScaler device. Specify the credentials of such a user in the NetScaler Username and NetScaler Password text boxes.

SSL

The eG agent collects performance metrics by invoking NITRO (NetScaler Interface Through Restful interfaces and Objects) APIs on the target NetScaler device. Typically, the NITRO APIs can be invoked through the HTTP or the HTTPS mode. By default, the eG agent invokes the NITRO APIs using the HTTPS mode. This is why, the SSL flag is set to Yes by default. If the target NetScaler device is not SSL-enabled, then the NITRO APIs can be accessed through the HTTP mode only. In this case, set the SSL flag to No.

Measurements made by the test
Measurement Description Measurement Unit Interpretation

Bridged Mbits

Indicates the rate at which Mbits forwarded to the NetScaler interfaces during the last measurement period.

Mbps

This is a good indicator of the load on the network interfaces.

Bridged packets

Indicates the number of packets forwarded to the NetScaler interfaces during the last measurement period.

Number

Collisions

Indicates the number of table collisions that occurred in the bridge during the last measurement period.

Number

When two or more interfaces attempt to transmit a packet over the bridge at the same time, a collision occurs. Packet collisions can result in the loss of packet integrity or can impede the performance of the NetScaler appliance.

Ideally therefore, the value of this measure should be 0. 

 

Loops

Indicates the number of loops that occurred in the bridge during the last measurement period.

Number

A loop occurs when there is more than one Layer 2 path between two interfaces in a VLAN. Typically, when a link aggregate channel configured on a NetScaler appliance is removed, the network interfaces bound to it induce network looks. Looping creates broadcast radiation - i.e., the accumulation of broadcast and multicast traffic on an appliance. Extreme amounts of broadcast traffic constitute a broadcast storm. A broadcast storm can consume sufficient resources so as to render the appliance unable to transport normal traffic.

Ideally therefore, the value of this measure should be 0.

Interfaces muted

Indicate the number of times the interfaces were muted during the last measurement table.

Number

An interface is said to be muted if it stops transmitting and receiving packets. This could be owing to dropped packets or because there were too many MAC moves on that interface or due to a suspected configuration issue.