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Chapter 4

Introduction to the Cisco IOS and SDM

The clock rate command is set in bits per second. Besides looking at the cable end to

check for a label of DCE or DTE, you can see if a router’s serial interface has a DCE cable con-

nected with the show controllers int command:

Todd#sh controllers s0/0/0

Interface Serial0/0/0

Hardware is GT96K

DTE V.35idb at 0x4342FCB0, driver data structure at 0x434373D4

Here is an example of an output that shows a DCE connection:

Todd#sh controllers s0/2/0

Interface Serial0/2/0

Hardware is GT96K

DCE V.35, clock rate 1000000

The next command you need to get acquainted with is the bandwidth command. Every Cisco

router ships with a default serial link bandwidth of T1 (1.544Mbps). But this has nothing to do

with how data is transferred over a link. The bandwidth of a serial link is used by routing pro-

tocols such as EIGRP and OSPF to calculate the best cost (path) to a remote network. So if you’re

using RIP routing, the bandwidth setting of a serial link is irrelevant since RIP uses only hop

count to determine that. If you’re rereading this part thinking, “Huh—what? Routing protocols?

Metrics?”—don’t freak! I’m going over all that soon in Chapter 6.

Here’s an example of using the bandwidth command:

Todd#config t

Todd(config)#int s0/0/0

Todd(config-if)#bandwidth ?

<1-10000000> Bandwidth in kilobits

inherit Specify that bandwidth is inherited

receive Specify receive-side bandwidth

Todd(config-if)#bandwidth 1000

Did you notice that, unlike the clock rate command, the bandwidth command is con-

figured in kilobits?

After going through all these configuration examples regarding the clock rate

command, understand that the new ISR routers automatically detect DCE

connections and set the clock rate to 2000000. However, you still need to

understand the clock rate command, even though the new routers set it for

you automatically!

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Cisco 2501 - Router - EN Manual do Utilizador Página 46