CCNA Examination achievement is dependent mainly on noticing the small print, and this is especially true of configurations involving directly related serial interfaces. And of course, it’s not plenty of to note these particulars – you’ve received to understand what to do about them!
A Cisco router is often a DTE by default, but instantly connecting two DTEs http://query.nytimes.com/search/sitesearch/?action=click&contentCollection®ion=TopBar&WT.nav=searchWidget&module=SearchSubmit&pgtype=Homepage#/먹튀검증 that has a DCE/DTE cable just isn't ample. In the subsequent case in point, R1 and R3 are right related at their Serial1 interfaces. The line goes up briefly following becoming opened, but the line protocol goes down right after about 30 seconds.
R3(config-if)#int s1
R3(config-if)#ip deal with 172.12.13.3 255.255.255.0
R3(config-if)#no shutdown
2d18h: %Backlink-3-UPDOWN: Interface Serial1, modified state to here up
2d18h: %LINEPROTO-five-UPDOWN: Line protocol on Interface Serial1, improved condition to up
R3(config-if)#
2d18h: %LINEPROTO-five-UPDOWN: Line protocol on Interface Serial1, modified state to down
The trouble is usually that one of the routers should act as the DCE in order for the road protocol to come back up and stay awake. If this were being your CCNA / CCNP household lab, you may just go over and look at the DTE/DCE cable to determine which router experienced the DCE end of the cable connected. In this instance, although, we don’t have Actual physical access to the routers. How can we convey to which router has the DCE stop of your cable connected?
R3#exhibit controller serial one
High definition unit one, idb = 0x1C44E8, driver construction at 0x1CBAC8
buffer measurement 1524 HD unit 1, V.35 DCE cable
The exhibit controller command presents us this information. (There’s a whole lot additional output that this with this particular command, nonetheless it’s unimportant for our reasons.) The router Using the DCE stop with the cable needs to produce a clock price for the DTE, and we’ll do exactly that Along with the interface-amount clockrate command.
R3#conf t
Enter configuration instructions, 1 per line. End with CNTL/Z.
R3(config)#int serial1
R3(config-if)#clockrate 56000
In just some seconds, the line protocol goes up and stays up.
When troubleshooting a relationship, usually operate exhibit interface to start with. If the thing is The mix revealed underneath, the link is physically fantastic but logically down. That’s normally the results of a required keepalive not staying present. With Body Relay, it’s possibly an LMI issue, but with instantly related serial interfaces The problem is most likely the DCE conclude of your link not providing clockrate.
R3#demonstrate interface serial 1
Serial1 is up, line protocol is down
Troubleshooting is a huge Element of the job, and it’s an enormous part of the Cisco CCNA and CCNP applications at the same time. Know your clearly show and debug instructions so you’re on your own solution to passing the CCNA!