Quick ? Regarding Serial Connections

[dave]

I am taking my CCNA in a couple days, and the only issue I have with the exam is the following:

They ask you to establish a serial connection between to labs (Router A and B), and be able to ping one router from the other. Set the clock rate on the DCE side, enable the interfaces (S0, S1), and set the encaps type were all that I thought you needed to do.. but apparently not. Also, the simulator on the exam doesnt allow you to set an encapsulation type. Quick responses would be greatly appreciated, thanks.

Dave Robinson

[james.henderson · Accepted solution]

You don't need to configure the encapsulation type if you are using the default.

All you need to do is configure the timing on the DCE side and enable the interfaces. But that is just for a generic back to back serial connection. If you are using Frame Relay or some other WAN protocol, it will need to be set up differently.

[dave]

I appreciate the response, but thats exactly what I did. The ask you to use the 192.168.128.0 networking scheme.. so I assigned one of the serial ports to 192.168.128.1 and the other to 192.168.128.2. The exact topology is as follows:

Lab_B (Router B) is connected to a switch, which has two hosts connected to it. You use on of these hosts to configure the router, and there are options to configure the host (Ip address, default gateway).

Lab_B is connected to Lab_C via a serial connection, Lab_B is the DCE side. The same setup (Switch, two hosts) is on the other lab.

I am definitely confused as to why it's not working.. I set the clock rate to 56000, do i need to set the bandwidth? I have to think that its my addressing, or some protocol related issue...

Dave

[fbarreras]

Perform the no shutdown command on the interface. Are you using CD that came with 640-607 certification guide?

[dave]

Yeh I am using that cd.. and I did do the no shutdown. Basically I think that I need to configure the host Im using to ping the router differently, I can only assume its my adressing. Regardless of what it is, its not working though..

Dave

[james.henderson]

Do you have your subnet mask set to 252?

do you have ip subnet-zero enabled?

Just make sure the IPs for your routers are set in the same subnet.

Are the interfaces on the routers up/up?

[dave]

No I didnt have my mask set to that.. the question said to use the default subnet masks (I assumed the default for class C). The interfaces are not up/up.. It must be related to what you just decribed.

[dave]

James:

If they ask me to use the 192.168.128.0 addressing, then how what addresses would you use for s0 and s1 (On router A, and router B)? And one last question, I have seen the subnet 0 command but haven't a clue what it does.. I have been checking the indexes of my cisco books but nothing. Thanks for your input,

Dave

[james.henderson]

a 24 bit subnet-mask is fine.

the ip subnet-zero command enables you to use the first octet of a subnetted network. Without ip subnet-zero, the first octet is wasted.

[dave]

hmm... im still only getting 2/5 points for this question.. and the serial links are still down/down. Anyone know if there is a number i can call, its really the only problem I am having with the course.

Dave

[dave]

Problem solved.. i think it was because I enabled the int before I set it up. Thanks for the help guys

Dave