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Community Member

Ethernet port shuts down

I have a cisco 2600 router with a single T1 DSU.

The Ethernet port occasionally shuts itself down. When this happens, I can telnet in through the serial (T1) port and issue a "no shutdown" command to bring it back up.

Any idea what could be shutting down the Ethernet port?


Community Member

Re: Ethernet port shuts down

I have seen "excessive" amount of errors on a e port shut it done before

have always found it to be a bad cat 5 cable or connection.

do a show interface and see if the errors are excessive

Community Member

Re: Ethernet port shuts down

2600 router's ethernet port is connected to which device? Is it to a Catalyst switch or something? Because on few catalyst switches there is something called "errdisable" ( Error Disable ). What it does is that it will disable a specific port if it detects too much of collisions, mismatch in duplex configuration, too many errors on the port due to layer one issues etc. So, I would suggest you to check the ethernet cable on 2600 that connects it to the LAN, check the port status on the switch (assuming it is a switch) etc. May be it is worth to check out the following URL

Community Member

Re: Ethernet port shuts down

The 2600 is connected via crossover cable to a Linksys Cable/router. This device performs NAT and port forwarding.

A show int command does not show excessive errors.

Ethernet0/0 is up, line protocol is up

Hardware is AmdP2, address is 0002.16ef.b0e0 (bia 0002.16ef.b0e0)

Description: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Internet address is x.x.x.x/29

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliablility 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

5 minute input rate 23000 bits/sec, 22 packets/sec

5 minute output rate 11000 bits/sec, 13 packets/sec

16363618 packets input, 2290707514 bytes, 0 no buffer

Received 32504 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

16942754 packets output, 3314804689 bytes, 0 underruns

15 output errors, 37132 collisions, 4 interface resets

0 babbles, 0 late collision, 55565 deferred

15 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Community Member

Re: Ethernet port shuts down

You may wand to "nail down" the speed and duplex of the ethernet port. Also when the interface shuts itself down you may want to telnet into the t1 interface and do the show proce cpu and mem commands see what's up with that. You might want to also capture a show tech for cisco to look at.

Community Member

Re: Ethernet port shuts down

I issued a debug command on the router, and am seeing tons of "dispose ip.hopcount messages. Are these normal? Can anyone tell me what they are?

They seem to be coming in over the serial frame port, but some of the referenced IPs are actually connected to the Ethernet port!

I can see the command to "nail down" the duplex, but which one is for speed?

Community Member

Re: Ethernet port shuts down

don't know about the dispose ip.hopcount messages but my bad on the speed deal. If it is a 10 mb card it will not have a speed command only duplex. To clarify nail down both sides of the ethernet to 10 half or 10 full.

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