Intel ER8100STUS - Express 8100 Router, Справочное руководство

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Reference.bok : Chapter01 6 Wed Apr 22 10:58:08 1998
6
WAN Services
LAN and WAN Services in the Router
Multiple backup links
For ISDN and X.25 services, it is possible to establish multiple backup links for
increased internetwork reliability. This can be a particularly useful feature in
X.25 networks where a number of Switched (dial-up) links can be available.
In the above example, link 4 is used if the primary link (link 2) should fail, link
5 is used if link 4 should fail and link 6 is used if link 5 should fail.
Timer Profiles
The Intel Express 8100 Router implements Timer Profiles which offer extensive
facilities to restrict WAN link activity according to a user-defined time profile.
This may be done for security reasons or to reduce the operating costs of WAN
links.
Up to 16 user-defined timer profiles can be defined, any one of which can be se-
lected for use with a WAN link during configuration of the link. Each profile al-
lows you to define access rights on a weekly basis, with a half-hour resolution.
For each link, access can be blocked:
■
for outgoing access from the router to the WAN link
■
for both outgoing and incoming access (WAN link disabled outside the times
defined in the timer profile)
For example, for one link using a timer profile, outgoing access may be block,
while for another WAN link using the same timer profile, access may be block
for all data traffic.
Timer profiles
consideration Warning
When blocking both outgoing and incoming access, the timer pro-
file must be the same in both the routers over the WAN link.
This is particularly important for dial-up (switched) WAN links where operating
costs are dependent on the use of the link.
If the timer profiles are not the same and only one of the routers is denying in-
coming access at some time, the other router may continually attempt to establish
the WAN link. This can lead to the following problems for the calling router:
■
for dial-up WAN links, excessive operating costs for the WAN link
■
error messages being logged
■
the link being disabled (faulted)
1235
Link 2
PPP
Leased
Line Link 4
X.25
Dial Up
Backup for Link 2 Link 5
X.25
Dial Up
Backup for Link 4 Link 6
X.25
Dial Up
Backup for Link 5