831 Interface Light Goes Out

[JSKoval]

I have a Cisco 831 that I had to put through password recovery. Ever since, I have not been able to connect to the LAN ports. What happens is that the router looks OK through most of the reboot, but just as it gets to the point where it says "Press Return to Get Started!" the LAN light goes dark, no matter which port I use. I've reseated the memory and upgraded the IOS to 12.3(2)XE3, but it hasn't made any difference. The ethernet0 config is very simple:

interface Ethernet0
ip address 10.1.1.98 255.255.255.0
ip access-group 100 in
ip nat inside
no cdp enable
hold-queue 32 in
hold-queue 100 out

Show int shows the interface as up and up. Can anyone give me any ideas where to go next? Thank you.

 

[KiscoKid]

Have you tried a different LAN cable? Ar you using a straight through or crossover cable? What kind of device is connected to the LAN port of the 800? As this is only an Ethernet port, is the device connected set to auto or 10mb/half or 10mb/full?

 

[JSKoval]

I did change cables. The router was connected to a relatively-new LinkSys switch, but with a straight cable. The LinkSys apparently has auto-crossover, because it was working with that cable before I did the password recovery. However, I tried another straight cable, as well as a crossover cable anyway, and it didn't make a difference. I've now got the router home, where it's been connected to a Netgear router with both types of cables--still the same. The router interface shows 10Mb/s with full duplex, but it won't allow the duplex command, so I can't try changing it.

 

[voltron1011]

Have you tried making a loopback cable tester with a spare RJ45 connector? This would be your best bet. Plus, it's really simple to do.

http://www.juniper.net/techpubs/software/nog/nog-interfaces/html/fe-ge-loopback25.html

 

[JSKoval]

I used a loopback connector in port 1 of the inside interface and a cable to a Netgear switch in port 4. When I reboot the router, lights for both port 1 and port 4 come on and stay on through almost the entire boot sequence, until right after

"Cisco C831 (MPC857DSL) processor (revision 0x400) with 44237K/4915K bytes of memory.
Processor board ID AMB083107YQ (1097041270), with hardware revision 0000
CPU rev number 7
2 Ethernet interfaces
4 FastEthernet interfaces
128K bytes of NVRAM.
12288K bytes of processor board System flash (Read/Write)
2048K bytes of processor board Web flash (Read/Write)"

and right before

"Press RETURN to get started!"

when both port 1 and port 4 lights go out. After that happens, the interface looks like this:

"Ethernet0 is up, line protocol is up
Hardware is PQUICC Ethernet, address is 0011.931b.841f (bia 0011.931b.841f)
Internet address is 10.1.1.98/8
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 10Mb/s
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:04:38, output 00:00:08, output hang never
Last clearing of "show interface" counters never
Input queue: 0/32/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/100 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
15 packets input, 900 bytes, 0 no buffer
Received 14 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
30 packets output, 1800 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out

 

[JSKoval]

SOLVED!!

I discovered that the 831 has a "Managed LAN" feature, where each port of ethernet0 is mapped to a fast ethernet interface. So to make port 1 of ethernet0 work, interface "fastethernet1" cannot be shutdown. Same for 2, 3, and 4. In my config, they were all shut down because I didn't understand where these phantom fast ethernet interfaces were. Therefore I had no idea they were in use. Once I applied "no shut" to each of the four fast ethernet interfaces, the lights came back on and the router worked well again.

Thanks to those who responded!