Vpi And Vci; Metric; Nailed-Up Connection (Ppp) - ZyXEL Communications Prestige 660W Series User Manual

7.4

VPI and VCI

Be sure to use the correct Virtual Path Identifier (VPI) and Virtual Channel Identifier (VCI) numbers
assigned to you. The valid range for the VPI is 0 to 255 and for the VCI is 32 to 65535 (0 to 31 is reserved
for local management of ATM traffic). Please see the appendix for more information.
7.5

Metric

The metric represents the "cost of transmission". A router determines the best route for transmission by
choosing a path with the lowest "cost". RIP routing uses hop count as the measurement of cost, with a
minimum of "1" for directly connected networks. The number must be between "1" and "15"; a number
greater than "15" means the link is down. The smaller the number, the lower the "cost".
The metric sets the priority for the Prestige's routes to the Internet. If any two of the default routes have the
same metric, the Prestige uses the following pre-defined priorities:
1. Normal route: designated by the ISP (see section 7.8)
2. Traffic-redirect route (see section 7.10)
3. WAN-backup route, also called dial-backup (see section 7.10)
For example, if the normal route has a metric of "1" and the traffic-redirect route has a metric of "2" and dial-
backup route has a metric of "3", then the normal route acts as the primary default route. If the normal route
fails to connect to the Internet, the Prestige tries the traffic-redirect route next. In the same manner, the
Prestige uses the dial-backup route if the traffic-redirect route also fails.
If you want the dial-backup route to take first priority over the traffic-redirect route or even the normal route,
all you need to do is set the dial-backup route's metric to "1" and the others to "2" (or greater).
IP Policy Routing overrides the default routing behavior and takes priority over all
of the routes mentioned above (see the IP Policy Routing chapter).
7.6

Nailed-Up Connection (PPP)

A nailed-up connection is a dial-up line where the connection is always up regardless of traffic demand. The
Prestige does two things when you specify a nailed-up connection. The first is that idle timeout is disabled.
The second is that the Prestige will try to bring up the connection when turned on and whenever the
connection is down. A nailed-up connection can be very expensive for obvious reasons.
Do not specify a nailed-up connection unless your telephone company offers flat-rate service or you need a
constant connection and the cost is of no concern
WAN Setup
Prestige 660W/HW Series User's Guide
7-3