Cabletron Systems STS16-20R, STS16-20D manual CrossLink Connections

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CrossLink Connections

Two or more Token-Ring ports can be configured to comprise a CrossLink.

A CrossLink is a collection of identical parallel links between two switches or between a switch and an end node, aggregated to appear as one single link of the aggregate capacity. The traffic distribution mechanism attempts to balance the load on the individual links. If one of the links in a CrossLink fails, the traffic is automatically moved from this link and distributed among the other links, thus providing active resilience.

The CrossLink ports on a STS16-20x switch can be used to connect to another STS16-20x switch, or a server with multiple RapidFire adapters using ClearServer for Token-Ring. (Please note that ClearServer for Token-Ring is supported on selected models of RapidFire adapters only. For details, refer to the ClearServer for LAN product information.)

The CrossLinks provide load distribution as well as resilience. In normal operation, the traffic is distributed on the physical ports of the CrossLink according to the frame MAC addresses. This ensures the sequence of a flow. Should a link fail or otherwise become inoperative, the switch dynamically redistributes the traffic to the remaining links. The CrossLink remains in operation as long as there is at least one link in operation. If a failed link is restored, traffic is once more redistributed to make use of the restored link.

A CrossLink is in many ways operating as one single link. For example, the spanning tree protocol will only have one port entity covering all ports in the CrossLink. The ports will all have the same operating state. As for VLAN and CRF configuration, the CrossLink is also seen as one link. Configuration changes apply to all links in the CrossLink.

On the STS16-20/RM/STS16-20FRM switch, CrossLinks can also be configured on the High-Speed Token-Ring ports of the SSIM-R2-02/SSIM-R8-02 High Speed Token Ring SmartStack modules or on the Fast Ethernet ports of the SSIM-H2-02 Fast Ethernet -Translational Switch SmartStack module. CrossLinks on Fast Ethernet ports can only consist of two ports available on the same SSIM-H2-02 Fast Ethernet -Translational Switch SmartStack module.

The CrossLink concept is designed to be compatible with the coming Link Aggregation standard, IEEE 802.3ad.

On SmartStack STS16-20D only the network ports 17–20 will allow CrossLinks. On this switch you can achieve up to 128 Mbps using four ports. On the SmartStack STS16-20R up to 256 Mbps can be achieved, using eight ports.

The STS16-20/RM/STS16-20FRM switch allows up to eight CrossLinks, each consisting of up to eight Token-Ring links.

Switch Overview SmartStack STS16-20D/STS16-20R Token Ring Switches Installation and User Guide