1. Home
  2. Cisco Certification
  3. Serial Connection not coming UP

Serial Connection not coming UP

I think that I'm having a problem with the serial interface. Here is the scenario, I have 3 cisco 2500 routers (2503, 2501, 2514). I'm trying to connect the router in a simple lab with the 2503 being in the middle connecting the 2501 via Serial 1 and the 2514 via Serial 0. From the 2514 I can ping the serial S0 of the 2503 router and vice versa. But I can't get the S1 interface to come up. It is always saying manually down after I run a "sh ip int brief", I've reloaded the routers, and swapped cables and still get the same result. I have clocking enabled on the interface since both interfaces are the DCE to the other two routers. When I do a sh cont serial 0 I see the cable as a V.35 but I'm using the standard back-to-back serial cable?? Is this weird?? Do you think it could be a bad interface?? Are there any other troubleshooting methods or diagnostics??? I have the config below, I threw RIP on the routers to see if they would communicate and populate the tables but they still wouldn't, possibly because they aren't learning because of the downed interface. If you want to see the other configs I can place them in here two. Any help will be appreciated, this is driving me crazy!!!

Thanks

version 12.1 no service single-slot-reload-enable service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname 2503 ! no logging console ! ! ! ip subnet-zero no ip domain-lookup ! ! ! ! nterface Ethernet0 ip address 192.168.3.1 255.255.255.0 ! interface Serial0 description DCE connection to 2514 ip address 192.168.1.1 255.255.255.0 no fair-queue clockrate 64000 ! interface Serial1 description DCE connection to router 2501 ip address 192.168.2.1 255.255.255.0 no fair-queue clockrate 64000 ! interface BRI0 no ip address shutdown ! router rip network 192.168.1.0 network 192.168.2.0 network 192.168.3.0 ! ip classless ip http server ! banner motd ^CC This is the 2503 router^C ! line con 0 line aux 0 line vty 0 4 login ! end

2503#sh ip int brief Interface IP-Address OK? Method Status Prot ocol BRI0 unassigned YES NVRAM administratively down down

BRI0:1 unassigned YES unset administratively down down

BRI0:2 unassigned YES unset administratively down down

Ethernet0 192.168.3.1 YES NVRAM up down

Serial0 192.168.1.1 YES NVRAM up up

Serial1 192.168.2.1 YES NVRAM down down

Reply to
matthewpascucci
Loading thread data ...

You're showing physical down on S1. This could be a number of problems:

1) Bad S1 interface on 2503. 2) Bad interface on 2501. 3) Bad cable. 4) Mis-configured 2501. (shutdown on interface)

You're in luck, however, in that you have a known good 2514, one known good interface on the 2503, and one known good cable. Check your 2501 config (easy stupid mistake), and then swap known good components against untested components until you find the problem. You don't even need to fiddle with changing addresses around for testing--all you're looking for is an "UP" or "DOWN" in the physical column to isolate the failure.

Reply to
Mike Dorn

Hi

Do you have the DCE end of the cable plugged into the router with the clockrate configured ?

Rgds

Jimmy

Reply to
Jimmy

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.