Ehternet Question

[Burnt_Offering]

I have a question concerning ethernet ports on my Cisco routers. I am currently studying for my CCNA, and am trying to do a "Hands on Lab" scenario. I'm using the Todd Lammle Fifth Edition study guide. Page 232 if anyone has it. I have 3 Cisco 2500 series routers. My problem is this. I am trying to bring up my Ethernet 0 port. The book wants me to assign an IP address to it. No sweat. I do what the book say to the letter, and do the "No Shut" command and I always get the same thing. "Ethernet 0 is up Line protocol is down".The book says that when I type in "sh int e0" that the IP they want me to assign to Ethernet 0 should show "C 192.168.10.1 is directly connected to FastEhternet 0" But it doesn't and no matter what I do, it won't. Any suggestions?

[Georg Pauwen]

Hello,

your Ethernet shows up/down because there is nothing connected to it. You either need to connect a device (router or PC) to the Ethernet port, or configure ´no keepalive´ in interface configuration mode in order to get the interface to up/up and to be able to see the directly connected network.

HTH,

GP

[Burnt_Offering]

Yo dude, man I appreciate the info. I did the no keepalive command and that did it. Todd Lammle is using the 2600 in the book, and it never says anywhere that I can see to do that. Anyway, the Lab I'm doing is having me connect the Ethernet on each router to a switch, and I only have one switch which is why nothing was connected to it. Anyway, I appreciate the quik help!!

[Kevin Dorrell]

Hi. Don't be deceived by what you see when you do no keepalive. If you do that then yes, the interface reports itself as up, but that is simply because it can no longer detect that it is down. The no keepalive fools it into believing that it is up, and of couse makes the route appear in the routing table as a consequence.

In a real network you would not normally use no keepalive - the interface would come up when connected to something, and go down when it is not. As you would expect.

Hope this clarifies things.

Kevin Dorrell

Luxembourg

[Burnt_Offering]

Thanks For the info Kevin. So the next question would be, when would it ever be appropriate to use that command if there is something connected to the interface?

[thisisshanky]

If there is something connected to the that interface, never use the no keepalive command. It should only be used in lab environments when you want an up interface, but u dont want to connect that interface to a switch or hub. With this command you could easily create problems such as - YOu could have a non routable interface due to a dead peer, bad cable, but still the interface will be up/up.

[Burnt_Offering]

Very cool, thanks again guys for the info

[Burnt_Offering]

Another question along the same lines. In my Lab scenario, my Serial interfaces will not stay up, and they ARE connected together using DTE cables. I can assign an ip address to Serial port 0, do the "no shut" command, and it will show "up" for about 10 seconds before it says "down" I am using 3 routers, and all of them are on as I'm doing this. All 3 do the same thing.

[Richard Burts]

I think the key to understanding your problem is your statement that the routers are connected using DTE cables. For the 2500 routers connected back to back, one of the routers on each connection must have a DCE cable, and must have the command clock rate . Without a clock rate the routers can not bring up the link and keep it up. And the clock rate can only be configured on interfaces with DCE cables.

HTH

Rick

[Burnt_Offering]

Well believe it or not I'm really not trying to confuse the issue. The calbes I'm using say DTE on one end, and DCE on the other. I have tried applying a clock rate of 64000 just before the "no shut command. THe study guide is very thourogh on instructions to the letter. It just doesn't tell you what to do if something goes wrong.

Here is the command structure.

Router(config)# hostname Lab_A

Lab_B(config)#enable secret Kevin

Lab_B(config)int s0

Lab_B(config-if)#ip address 192.168.20.2 255.255.255.0

Lab_B(config-if)#description WAN connection to Lab_A

Lab_B(config-if)#clock rate 64000

Lab_B(config-if)#no shut

It's at this point it says it's up. And about the time you start typing the next command it's down. Driving me crazy. Does it matter which end of the cable is plugged in to the different routers? I know this is all elementary to you guys, I appreciate the help. Any suggestions would be welcome.

Kevin

[Richard Burts]

In this post you entered the command hostname Lab_A and the name on the router changed from Router to Lab_B. Are you pasting commands from two different router sessions? If you do not give us consistent information it is difficult for us to analyze and understand what is going on.

Instead of showing what you typed, please post the output of show run so we can see if the clock rate is on the interface or not. It might also be helpful if you post the output of show controller serial.

The command clock rate needs to be on the interface with the DCE cable. I can not tell from the information that you provided whether you entered it on the interface with DCE or DTE. Can you clarify?

HTH

Rick

[Burnt_Offering]

OK, I finally got it. By piecing together what I already knew, and what you guys were telling me, I got it all working. I can now ping all the way accross 3 routers with the current config I have. All serial interfaces are up and running smoothly. So are my Ethernet ports with the no keepalive command as there is currently nothing connected to them.

Thank you all very much for all the help.

Kevin Monson