Allied Telesis AT-8400 Series Reference Manual page 45

You can also have link redundancy from an AT-8413 line card to another
type of Ethernet switch. The example in Figure 14 shows link backup to
an AT-8000 Series switch that has two Gigabit Ethernet expansion
modules, one with a twisted pair port and one with a fiber optic port.
Figure 14 AT-8413 Line Card Port Redundancy - Example 3
How the AT-8413 line card selects the active link is straightforward. It
assigns the active status to whichever port is first to establish a link with
its opposite port. That link remains as the active link until the link is lost.
At that point, the backup link becomes the active link, and remains so
until there is a change to its link status.
The actual process of activating a disabled port and establishing a link
can take the line card several seconds to complete. This may result in
some data loss during the few seconds required by the line card to
establish the new link.
If you have links to both the twisted pair and the fiber ports and you
reset or power cycle an AT-8400 Series switch, the switch defaults to the
fiber optic port first. In general, a fiber optic port is quicker at
establishing a link than a twisted pair port.
There is no software management required to use this feature.
Connecting the data cables and allowing the line card to establish an
active link is all that is necessary. It should be noted that you cannot
designate the active link through the AT-S60 management software. As
explained, the line card determines that automatically.
AT-8400 Chassis Installation Guide
1 2 3 4 5 6
AT-8411
AT-8411 AT-8413 AT-8411 AT-8411 AT-8411
TX GB/T TX TX TX TX
PWR PWR PWR PWR PWR PWR
L/A
1000
BASE-X
L/A D/C
10/1001000
BASE-T
LNK ACT LNK ACT LNK ACT LNK ACT LNK ACT
10 100
10 100 10 100 10 100 10 100
EJECT EJECT EJECT EJECT EJECT EJECT
AT-8024
10Base-T / 100Base-TX Fast Ethernet Switch
Link
Mode
Link
Mode
MODE
COL
FAULT
100
MASTER
FULL
ACT
PWR
31