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Community 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?



Community Member

Re: Can't ping Serial Interfaces!?

Having a problem in the serial interface itself is possible, but unlikely to happen, you are experiencing a physical layer problem, it is either a problem you have in your CSU/DSU or in the cable connecting the router to the dsu or the other router in case you have a back-to-back connection.

Can you post your DCD, DSR, DTR, RTS and CTS status on the interface? (The last line of the "show interface s1" output)

How is your router connected? Is it to a CSU/DSU or just back to back with another router?

It may help if you can apply a loop in your csu/dsu to test the cable, or if you have another cable, try replacing the existing one and see how it goes.

If you have the interface in "shutdown" status, you won't see its route in the routing table whether everything is OK or not in your router. So, "show ip route" output won't have the interface IP network there. Look into layer-1.


Re: Can't ping Serial Interfaces!?

Are keep alive and encapsulation OK?

Community Member

Re: Can't ping Serial Interfaces!?

If he has encapsulation or keepalive mismatch, he would have "protocol" down, not "interface down". "interface down" is for sure a physical problem somewhere either a problem in hardware/cable, or one or both end are not receving clocking properly.

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