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Chapter 2 Installation
Creating Connections
2-12
Catalyst GigaStack Gigabit Interface Converter Hardware Installation Guide
78-6460-04
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
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.
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2
Catalyst 3500
XL
1
Port 1
Redundant
link
Port 2
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Y
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Catalyst 3500
XL
7
8
3
5
6
4
2
1
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P
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D
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Y
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9
10
1
1
1
2
2
Catalyst 3500
XL
12
34
56 78
1
1
2
1
2
1
2
9
1
0
1
1
1
2
12
34
56 78
13 14
15 16
17 18 19 20 21 22 23 24
Catalyst 3508G XL
Catalyst 3512 XL
Catalyst 3524 XL
1X
2X
11X
12X
1X
2X
11X
12X
13X
14X
15X
16X