"no shut" serial 1

[ldenison]

I have recently purchased the Cisco CCNA training package. ONe of the labs instructs one to execute a "no shut" command on a serial port. After doing so the line goes up; however 30 sec later it goes back down.

[juniper]

Im assuming you are connecting the serial interface to another cisco serial interface so look at the cable one end says DTE and the other says DCE now on the one that says DCE type

config t
int s1
ip address 192.168.0.1 255.255.255.252
clock rate 64000
no shut


only do this on the DCE one as it needs to supply timing for the line. (Its emulating the ISP)

on the other side (DTE) type

config t
int s1
ip address 192.168.0.2 255.255.255.252
no shut

also remember serial 0 is the first interface and serial 1 is the second interface Thye always start with 0.

[Erik]

Basically there are two things that need to be brought up for the interface to be operational. The interface itself, and the line protocol. If you have nothing connected to the other end of the interface it will be up, but not really because the line protocol won't be up. This just means that it is waiting for a connection to another device.

As mentioned you need to have two routers connected together back to back with a DCE-DTE cable. A clock rate must be set on the DCE side ONLY. Then the interface will come up and stay up. Actually even when it says down as you are experiencing it will pop up as soon as you connect it to another up interface. The only time an interface is down and will never come up is when it is administratively down, meaning you issue a shutdown command.

[ldenison]

how can you tell whether its DCE or DTE? Also remeber this is a simulator, there are no physical connections. I took your advice and it still shuts down after 30 sec.

[juniper]

OH! I thought you purchased a CCNA lab kit that had real routers and cables (like off e-bay) . what simulator package did you buy?

[ldenison]

thanks guys. it worked. i had to set ip address and clock rates on both routers and it works now. thanks

[Erik]

No, you shouldn't be setting clock rates on both routers. In real life you would be connecting a router to a DCE device, provided by the ISP. This is your WAN connection. When you set a clock rate on a router you are simulating this. So your setup sould be the DCE device (incoming internet) connected to a router (DTE device). Both interfaces wil need IP addresses and subnet masks, and the no shutdown command.

[juniper]

Love those simulators hehe, I truly recommend getting real routers. Basicly in the real world only one device can keep the timing on the line (otherwise you get two different timing signals) by default the router will use the "line timing" meening it is letting the DCE (ISP) provide the signal and it is listening for that. There are different timing methods the most common is B8ZS (bipolar 8-zero substitution) which means every 8 bits reverse the signal so now zeroes are positive volts (or 1's), then 8 more bits they are now zeroes again, (bipolar) this way if a long lines of zeros come through it can determin exactly how many zeros there where, as a digital zero is usualy no signal. The only time you should be setting timing on the router is in simulation or if the telco does not provide it like over "dark fiber", from my experience.

[ldenison]

ok,so i started off with a new simulator and its not working again. it did the same steps as before, like configuring both routers' serial ports to be on the same network and same ip address and it is still going down 30 sec later

[juniper]

I can only tell ya how to do real routers without knowing what simulator you are using.

[ldenison]

juniper, thank you. like i said, i'm new to this. I'm using Cisco CCNA Network Simulator 5

[juniper]

Im assuming you have boson netsim 5? I just downloaded demo and to setup click on new and click on 2500 then pick a 2501 and drag it over then do it again then drag a serial line over it will have a popup and ask which router and interface to use selct the first router s1 and then the second router s1 it will now prompt which one you want to be the DCE end for clocking (this will be the one you use the clock rate command on) select router1 when done select load into simulator and confiure like my example above.

[Variable]

Juniper, he said he is using Cisco CCNA Network Simulator 5. In the Cisco classes they have a router sim. It is not full featured. You basically can run through labs.

[juniper]

ah never heard of it LOL! I just did a google on CCNA simulator 5 and Boson's simulator version 5 was the first hit. Ok I added cisco to it and got the correct thing I think.

[juniper]

Hold on I read the bottom of the link and it says published by cisco, software by Boson? is this it?

http://www.bookpool.com/SSSSSS_C523/sm/1587201313

and why in the world would a cisco class use simulators? I took the network academy in 1998 and had real routers. (they where expensive back then too)

<Edit> more digging, Its the same software Variable just packaged with a cisco press book, simulator is by Boson.

[Erik]

Yeah it is a limited version of the Boson software that comes with Cisco Press books would be my guess.

When I took the Academy classes they had real routers for us to use. I think it is actually one of the requirments for a school to be part of the program is to have certain amount of equipment available for students. My guess would be that it is just easier to have them use a CD rather than dragging out racks and cables. Not nearly the same level of experience and satisfaction as using actual routers, but at least it is something.

[Variable]

The router sim that comes in the Cisco classes comes with the books and is online at the Cisco academy student site. It is built into the curriculum. If you are using the online portion of the class then the router sims are part of the lesson plans, testing is online. The sims in the exams mirror the sims in the book and academy site. Everyone uses router pods in Cisco academy classes...that’s a given : )

The sims give you repetitive command practice. Cisco commands are (purposely IMO) obtuse. With the pods you have to configure the wires to change scenarios. The sims give you the ability to change scenarios quickly and focus on the hard part - remembering the sequence of commands needed to configure the IOS. The hardware part is not nearly as difficult as the software configuration.

[czarg]

Hi,
I use Boson 5.25 version. The serial link shuts down like you said in some 30secs after 'no shut' but it is up again immediately the connecting link is up. here is what i mean:
if Router A and Router B have a serial link to each other. The serial link on A will shut down till the serial link on B is configured.
This means the 'shut down' is only temporary. does it read 'interface s0 down, protocol up' on your simulator?

hope this helps you.