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Designing ISDN Internetworks 11-27

Tariff Management

Controlling IPX Watchdog Packets

NetWare servers send “watchdog” packets to clients and disconnect any clients that do not respond.

When IPX watchdog spooﬁng is enabled, the router local to the NetWare server responds to

watchdog packets on behalf of the server’s clients. IPX watchdog spooﬁng allows clients to remain

attached to servers without having to constantly send packets across the ISDN link to do so. This

feature is particularly important when trying to control ISDN link up time. The interface

conﬁguration command for enabling IPX watchdog spooﬁng is ipx watchdog-spoof.

Controlling SPX Keepalive Packets

Some Sequenced Packet Exchange (SPX)-based services in the Novell environment use SPX

keepalive packets. These packets are used to verify the integrity of end-to-end communications when

guaranteed and sequenced packet transmission is required. The keepalive packets are generated at a

rate that can be adjusted by the user from a default of one every 5 seconds to a minimum of one every

15 minutes. SPX spooﬁng as implemented in the Cisco IOS software receives, recognizes, and

successfully acknowledges keepalive packets both at the server end and the client end.

Time Server and NDS Replica Packets

NetWare 4.x includes a time synchronization protocol that causes NetWare 4.x time servers to send

an update every 10 minutes. To prevent the time server from generating update packets that would

cause unwanted connections, you need to load a NetWare-loadable module (NLM) named

TIMESYNC.NLM that allows you to increase the update interval for these packets to several days.

A similar problem is caused by efforts to synchronize NDS replicas. NetWare 4.1 includes two

NLMs, DSFILTER.NLM and PINGFILT.NLM, that work together to control NDS synchronization

updates. Use these two modules to ensure that NDS synchronization trafﬁc is sent to speciﬁed

servers only at the speciﬁed times.

AppleTalk

The AppleTalk Name Binding Protocol (NBP) converts entity names into numeric addresses. NBP

can transmit a signiﬁcant amount of trafﬁc throughout the network regardless of the named entity’s

location. This in turn can cause excessive dial-on-demand triggers. Applications such as

QuarkXpress and 4D use all zone NBP broadcasts to periodically probe the network either for

licensing purposes or to provide links to other networked resources. The debug apple nbp command

with the debug dialer command monitors NBP trafﬁc and can help you determine the kinds of

packets that cause connections to be made.

NBPTEST, an option when executing an AppleTalk ping command, is also useful when locating

particular nodes that are transmitting NBP broadcasts.

Beginning with Cisco IOS Software Release 11.0, you can ﬁlter NBP packets based on the name,

type, and zone of the entity that originated the packet. AppleTalk NBP ﬁltering allows Cisco routers

to build ﬁrewalls, dial-on-demand triggers, and queuing options based on any NBP type or object.

For a conﬁguration example, see “Using ISDN Effectively in Multiprotocol Networks” in the

Internetworking Case Studies publication.

Ultimately, if the applications that use NBP have been isolated, consult the individual vendors and

ask for their advice on how to control or eliminate NBP trafﬁc.

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Cisco 1003 - 1003 Router Bedienungsanleitung Seite 27