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750 Appendix A: Answers to the "Do I Know This Already?" Quizzes and Q&A Sections
9
Describe the metric(s) used by IPX RIP in a Cisco router.
The primary metric is a counter of timer ticks. If two routes to the same network tie with
the ticks metric, the hop count is considered. Ticks are increments of 1/18ths of a second.
The number of ticks is not measured but is set with defaults of 1 on LAN interfaces and 6
on WAN interfaces. The IPX delay interface subcommand overrides the defaults.
10
Does IPX RIP use Split Horizon?
Split horizon means that routes learned via updates received on interface x will not be
advertised in routing updates sent out interface x. IPX RIP uses split horizon by default.
SAP also uses split horizon concepts.
11
True or false: RIP and SAP information is sent in the same packets. If true, can only one
of the two be enabled in a router? If false, what commands enable each protocol globally
in a router?
False. Only one command is used, and it enables both: ipx routing. Neither type of update
is sent unless IPX is also enabled on the interface with the ipx network interface
subcommand.
12
What does GNS stand for? Who creates GNS requests, and who creates GNS replies?
GNS stands for Get Nearest Server. Clients create the request, which is a broadcast
looking for a nearby server. Servers and routers reply, based on their SAP table, with the
IPX address of a server whose RIP metric is low.
13
Define the term separate multiprotocol routing in the context of the Cisco IOS and Novell
IPX.
Separate multiprotocol routing means that each routed protocol, such as IP, IPX, or
AppleTalk, uses a separate set of routing protocols, which each send separate routing
updates to advertise routing information.
14
How often does a router send SAP updates, by default?
Every 60 seconds.
15
If Serial0 has a bandwidth 1544 interface subcommand and Serial1 has a bandwidth 56
interface subcommand, what metric will IPX RIP associate with each interface?
The IOS is unaffected by an interface's bandwidth when considering IPX RIP metrics;
ticks will default to 6 for any serial interface, regardless of bandwidth setting.
16
True or false: Routers forward SAP packets as they arrive but broadcast SAP packets on
interfaces in which no SAP packets have been received in the last 60 seconds.
False. Routers never forward SAP packets, but they instead read the information in the
updates, update their own SAP tables, and then discard the packets. Routers also send SAP
updates every update timer (default 60 seconds), regardless of what other routers may do.
apA.fm Page 750 Monday, March 20, 2000 5:24 PM