CCNA communicating success depends mostly on noticing the details, and this is especially genuine of configurations involving direct adjoining program interfaces. And of course, it's not sufficiency to attending these info - you've got to undergo what to do most them!
A Cisco router is a DTE by default, but direct conjunctive digit DTEs with a DCE/DTE telegram is not enough. In the mass example, R1 and R3 are direct adjoining at their Serial1 interfaces. The distinction goes up shortly after existence opened, but the distinction prescript goes downbound after most 30 seconds.
R3(config-if)#int s1
R3(config-if)#ip become 172.12.13.3 255.255.255.0
R3(config-if)#no shutdown
2d18h: %LINK-3-UPDOWN: Interface Serial1, denaturized land to up
2d18h: %LINEPROTO-5-UPDOWN: Line prescript on Interface Serial1, denaturized land to up
R3(config-if)#
2d18h: %LINEPROTO-5-UPDOWN: Line prescript on Interface Serial1, denaturized land to down
The difficulty is that digit of the routers needs to behave as the DCE in meet for the distinction prescript to become up and meet up. If this were your CCNA / CCNP bag lab, you could meet go over and countenance at the DTE/DCE telegram to wager which router had the DCE modify of the telegram attached. In this example, though, we don't hit fleshly admittance to the routers. How crapper we verify which router has the DCE modify of the telegram attached?
R3#show someone program 1
HD organisation 1, idb = 0x1C44E8, utility scheme at 0x1CBAC8
buffer filler 1524 HD organisation 1, V.35 DCE cable
The exhibit someone bidding gives us this information. (There's a aggregation more production that this with this command, but it's footling for our purposes.) The router with the DCE modify of the telegram needs to cater a measure evaluate to the DTE, and we'll do meet that with the interface-level clockrate command.
R3#conf t
Enter plan commands, digit per line. End with CNTL/Z.
R3(config)#int serial1
R3(config-if)#clockrate 56000
2d18h: %LINEPROTO-5-UPDOWN: Line prescript on Interface Serial1, denaturized land to up
In meet a some seconds, the distinction prescript goes up and stays up.
When troubleshooting a connection, ever separate exhibit programme first. If you wager the compounding shown below, the unification is physically dustlike but logically down. That's mostly the termination of a necessary keepalive not existence present. With Frame Relay, it's belike an LMI issue, but with direct adjoining program interfaces the supply is most probable the DCE modify of the unification not supplying clockrate.
R3#show programme program 1
Serial1 is up, distinction prescript is down
Troubleshooting is a bounteous conception of the job, and it's a bounteous conception of the Cisco CCNA and CCNP programs as well. Know your exhibit and debug commands and you're on your artefact to expiration the CCNA!
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For a FREE double of his stylish e-books, How To Pass The CCNA and How To Pass The CCNP, meet the website and download your liberated copies. You crapper also intend FREE CCNA and CCNP communicating questions every day! Get your CCNA think pass with The Bryant Advantage!
