Specifications

4-96
Reference Guide
Model No.
Running Head
WAN Card Redundancy System Configuration and Operation
During a WAN redundancy switch, voice and data traffic are momentarily disrupted, and
transmission then recovers automatically.
4.27.1 Cross-Connect WAN Card Redundancy Switching
In cross-connect systems, WAN redundancy requires a WAN-R DUAL card in slot W4 (as
marked on its faceplate ejector). This card becomes a redundant card for the WAN cards in
slots W1 through W3 if it is equipped with matching DSX/CEPT, CSU, or HDSL modules,
and if those modules are installed in the same positions on both WAN cards. This protection
scheme is known as 1-in-N redundancy. When a switch occurs, a relay on the WAN-R card
switches the output of that card to the corresponding pins on the WAN connector of the
Interface card.
The following restrictions apply to cross-connect WAN redundancy:
You must install the WAN-R card in slot W4 for redundancy.
If you install it in slot W1,
W2 or W3, it will work only as a standard WAN card with two ports.
If the plug-in modules on the WAN-R card do not match those on a card in slot W1, W2,
or W3, the WAN-R card will not behave as a backup for that active WAN card.
The
system will not reject the card, but it will not switch even if the active WAN card fails.
If a standard WAN card is in slot W4, the system does not support WAN redundancy.
In cross-connect systems, switching always occurs on both ports of a WAN card. Therefore,
both ports of all active WAN cards must have the same plug-in modules as the redundant-card
ports.
Figure 4-65 shows a System Main Screen for a cross-connect system with WAN card
redundancy. In this example, the CSU ports of the WAN cards in slots W1, W2, and W3 are
backed up by the CSU ports of the WAN card in slot W4. The redundant WAN card in slot W4
takes over for the first active WAN card that fails.