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New Member

Can't ping serial interfaces!?

Yo, I just got a 2507 router with 1 ethernet, 2 Serial Interfaces and I can't get either Serial to work. I've tried the basic [ip add, no shut, clock rate, bandwidth] configerations but no matter what I do it always says "Serial1 is down, Line protocal is down" when I do a [show int]. I can't ping the interface and when I do a [show ip route] it only shows the ethernet network. Any suggestions or are the interfaces faulty?




Re: Can't ping serial interfaces!?

It seems unlikely that both serial interfaces would be faulty. Down/Down indicated that it if not seeing the correct signals from the CSU/DSU. I would be checking that.

New Member

Re: Can't ping serial interfaces!?

i think yor both the serial port are not fine, check them and then try....


Re: Can't ping serial interfaces!?

You can ping all day and all night, but if you don't have those serial interfaces connected to something and up/up (vs. shutdown or disconnected) you won't get a response from the IP addresses you assigned to them.

You won't see the corresponding subnets in your route table, either, unless you have redundant connections and dynamic routing protocols telling your router how to find its way to those subnets through alternate paths.

What you're describing sounds like normal behavior for Cisco routers. I don't think there's anything wrong with your serial ports.

You need to get another router and a serial cross-over cable to test this. And either a single DCE-to-DTE back-to-back router cable; or two regular cables, one DCE and the other DTE, with the appropriate genders on the connectors so you can plug them both together forming a DCE-to-DTE link. Connect the two routers using this cable, and on the router with the DCE end run the clock rate command on that serial interface. Also, make sure your serial encapsulation matches on both ends (either HDLC or PPP).

When you get that serial link up, you should see your assigned IP addresses and subnet.

Hope this helps.

New Member

Re: Can't ping serial interfaces!?

i just got two 2500 series routers with 1 ethernet and 2 serial interfaces i cant get them talk together.

I've tried (ip address,no shut,clock rate)configuration the serial stays up the protocol goes down after 10 sec.

However when i put" no keepalive" the serial and the protocol stay up but no input packets .

Otherwise i cant ping the interfaces.

Thanks in advance.

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