Cisco 1003 - 1003 Router Bedienungsanleitung PDF herunterladen (Seite 25)

Designing ISDN Internetworks 11-25

Tariff Management

forth. The distribute-list in command causes the router to use access list 1 to ﬁlter networks learned

from RIP and allows only those networks that match the list to be redistributed into Enhanced IGRP.

This prevents route feedback loops from occurring.

The default-metric router conﬁguration command in the Enhanced IGRP portion of the

conﬁguration assigns an Enhanced IGRP metric to all RIP-derived routes. The ﬁrst value (128)

speciﬁes a minimum bandwidth of 128 kbps. The second value (100) speciﬁes a route delay in tens

of microseconds. The third value (255) speciﬁes the connection is guaranteed to be 100 percent

reliable. The fourth value (1) speciﬁes the effective bandwidth of the route. The ﬁfth value (1500)

speciﬁes in bytes the maximum transmission unit (MTU) of the route.

The default-metric router conﬁguration command in the RIP portion of the conﬁgurations causes

RIP to use the same metric value (in this case, a hop count of 2) for all routes obtained from

Enhanced IGRP. A default metric helps solve the problem of redistributing routes that have

incompatible metrics. Whenever metrics do not convert, using a default metric provides a reasonable

substitute and enables the redistribution to proceed.

The passive-interface router conﬁguration command declares an interface to be passive. When an

interface is passive, Enhanced IGRP excludes the interface from routing update broadcasts. If you

do not want to run RIP across the ISDN link, you can use the passive-interface command and static

routes.

Access Lists

Depending on the protocols that your network runs, you might need to use access lists to control

routing update packets that snapshot routing does not control. Or, depending on your network

design, you might not be able to use snapshot routing, in which case, access lists must be used to

control routing updates. This section describes access list techniques for controlling the following

types of trafﬁc:

• IP Enhanced IGRP Packets

• SNMP Packets

• Banyan VINES, DECnet IV, and OSI Packets

• IPX Packets

IP Enhanced IGRP Packets

You can use one of the following two access lists to control Enhanced IGRP trafﬁc:

access-list 101 deny eigrp any any

access-list 101 deny ip any 224.0.0.10 0.0.0.0

The ﬁrst access list denies all Enhanced IGRP trafﬁc and the second access list denies the multicast

address (224.0.0.10) that Enhanced IGRP uses for its updates. When you use access lists to control

Enhanced IGRP trafﬁc, you need to conﬁgure static routes to create routes across the ISDN link.

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Cisco 1003 - 1003 Router Bedienungsanleitung Seite 25