Hello. I'm trying to follow the CBT Nuggets for the CCNP Route exam. I have the GNS3 lab files and they are worked fine until I have gotten to the OSPF labs. For some reason, in all of the OSPF labs, there is a serial link between two routers that the line protocol is down. The configs came from CBT Nuggets and looking at them, I can not see any layer 2 problems. Has anybody seen a problem with serial interfaces and GNS3? Any help would be much appreciated.

I never had any issues setting up a simple point to point connection in GNS3 using serial links!

You need to configure L2 connection for the point to point link before implementing L3 (i.e. OSPF).

All you need to do for a simple connection is the following. Please make sure to do the same on both routers.

config#ip int s0/0
(config-if)#encapsulation ppp
(config-if)#clock rate 64000

And you should know the rest!!

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GNS3 video tutorials and how to's: http://www.youtube.com/GNS3Talk

please show your lab topology and the setting of the devices to us
or we can't help you troubleshooting your problem

I've uploaded the GNS3 .net file for the lab and also the configs for the two routers (R2 and R5) that the serial line protocol is down when I open the lab and start the routers.

Examing from the files, i can't see any wrongs with your setting, below were some of the reasons i guessed for the line protocol down

1 You may connected the wrong ports, maybe you connected R5:s0/0<------>R2:s0/1, but the right way should be R5:s0/0<------>R2:s0/0
(Mayby show us the pictures of your topology,cause no one can open your file "BasicOSPF.net" because of the different type and
location of the IOS from one PC to another)

2 You may forgot to "no shutdown" one of the serial port on R5 or R2

3 I thinks it had nothing to do with the OSPF protocol, if you had did the right setting: the IP address、the right connected、and the DCE/DTE clock, i think the protocol will be up automatically

Wish you can make it !

It HAS to be the clock rate and it HAS to be something dumb GNS3 is doing with the serial links. OP, check your running config for the 'clock rate 2000000' command on the culprit serial links. Also, 'show controllers sx/x' to determine DCE and DTE. But what do ya know? They're both DCE's. I'm no cisco guru but i'm pretty sure one is supposed to be the DCE (responsible for clock rate) and the other the DTE. If I'm right, how has GNS3 ever worked over serial connections lol?

I tried removing the clock rate 2000000 command from R5's startup config but it STILL returns. 'No clock rate 2000000' under the s0/0 int on either router also does not remove the clock rate. What gives?

*UPDATE*

I started over and now am seeing success. Both R2 and R5 S0/0 interfaces have the clock rate set and are DCE's.. :/

Hi,

Forget about DCE/DTE and clock rates. Dynamips doesn't accurately emulate the physical layer, remember this is not real hardware behind the scene!

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Jeremy, GNS3 Programmer & Benevolent Dictator for Life.

Any tips on how we can avoid this in the future? I wasted my morning on this!