CCNA exam success depends mostly on noticing the main points, and this is especially true of configurations involving straight related serial interfaces. And naturally, it’s not ample to notice these aspects – you’ve acquired to be aware of how to proceed about them!
A Cisco router is a DTE by default, but directly connecting two DTEs having a DCE/DTE cable is not ample. In the subsequent instance, R1 and R3 are right related at their Serial1 interfaces. The road goes up briefly just after staying opened, but the road protocol goes down soon after about 30 seconds.
R3(config-if)#int s1
R3(config-if)#ip handle 172.twelve.13.3 255.255.255.0
R3(config-if)#no shutdown
2d18h: %Backlink-three-UPDOWN: Interface Serial1, altered condition to http://www.bbc.co.uk/search?q=먹튀검증 up
2d18h: %LINEPROTO-five-UPDOWN: Line 토토사이트 protocol on Interface Serial1, changed point out to up
R3(config-if)#
2d18h: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed point out to down
The situation is the fact that on the list of routers ought to act since the DCE to ensure that the road protocol to come up and stay up. If this were your CCNA / CCNP residence lab, you could possibly just go in excess of and consider the DTE/DCE cable to check out which router experienced the DCE conclude in the cable attached. In this example, while, we don’t have Bodily usage of the routers. How can we inform which router has the DCE close with the cable hooked up?
R3#demonstrate controller serial one
High definition device 1, idb = 0x1C44E8, driver construction at 0x1CBAC8
buffer dimensions 1524 HD device 1, V.35 DCE cable
The clearly show controller command gives us this information and facts. (There’s quite a bit additional output this using this type of command, but it surely’s unimportant for our purposes.) The router Using the DCE conclude in the cable needs to provide a clock charge into the DTE, and we’ll just do that with the interface-degree clockrate command.
R3#conf t
Enter configuration commands, one particular for every line. Conclusion with CNTL/Z.
R3(config)#int serial1
R3(config-if)#clockrate 56000
In just a couple seconds, the line protocol goes up and stays up.
When troubleshooting a link, always run clearly show interface very first. If the thing is The mixture proven under, the link is physically fantastic but logically down. That’s usually the result of a essential keepalive not remaining current. With Body Relay, it’s possibly an LMI problem, but with directly linked serial interfaces The problem is almost certainly the DCE conclude from the relationship not giving clockrate.
R3#display interface serial 1
Serial1 is up, line protocol is down
Troubleshooting is a big Portion of the job, and it’s a giant A part of the Cisco CCNA and CCNP courses at the same time. Know your exhibit and debug instructions and you also’re in your way to passing the CCNA!