Cisco Systems WS-X3500-XL manual Catalyst 3512 XL Catalyst 3524 XL

Chapter 2 Installation

Creating Connections

Cascaded Stack Connections with a Redundant Link

You can form a redundant link by connecting the open ports on the top and bottom GigaStack GBICs within the same stack, as shown in Figure 2-8.

Figure 2-8 Cascaded Stack Connections with a Redundant Link

Catalyst 3508G XL

1 2 3

4 5 6

Port 1 Port 2

Catalyst 3500 XL

7 8

1 2

Catalyst 3512 XL

1 2 3 4 5 6 7 8

Catalyst 3524 XL

Catalyst 3500 XL

1 2

Redundant link

1 2 3 4 5 6 7 8 13 14 15 16 17 18 19 20 21 22 23 24

Catalyst 3500 XL

1 2 31116

The GigaStack GBIC software detects the loop configuration by the way the cables are connected and the number of switches used in the stack. The software uses one of the GigaStack GBIC links as the redundant link, which is disabled for data transmission while all the other links in the stack are up. When any other link in the stack is down, the redundant link is automatically enabled for data transmission. To ensure continued connectivity, the software periodically checks for changes in the stack and invokes the loop detection algorithm if a new link is added to the cascaded stack or if a link is removed from the cascaded stack.

GigaStack GBICs installed in a stack support a loop configuration only if every Catalyst 2900 XL and 3500 XL switch in the stack is running IOS software Release 12.0(5)XU or later, Release 12.1(6)EA2 or later for Catalyst 2950 switches, and Release 12.1(4)EA1 or later for Catalyst 3550 switches.

For Catalyst 2900 XL and 3500 XL switches running IOS software earlier than Release 12.0(5)XU, an illegal loop is created under these conditions:

•A GigaStack GBIC is connected to two other GBIC ports in the same stack.

•A single GigaStack GBIC cable is inserted in port 1 and port 2 of the same GBIC.

	Catalyst GigaStack Gigabit Interface Converter Hardware Installation Guide
2-12	78-6460-04