Ethernet Interface problems

[pjgordon64]

I am having trouble pinging any devices connected to an ethernet interface on a 2600 router. sh cdp neighbors doesn't show anything even though the ethernet cable is connected to a 2950 switch.

Show interfaces has this information:

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

Last input 00:35:15, output never, output hang never

The ARPA table is empty except for the interface address. If I manually map an ip address to its mac address, I still can't ping that address.

The interface is up and up. The keepalive is set, so it must be communicating with somethign, right?

When I turn on "debug ip packets" and then try to ping, I get error messages with the packets --"ecapsulation failure".

Anyone have any ideas?

Paul

[glen.grant]

What addresses and mask do you have on the ethernet interface and also the 2950 . I assume they are both in the same subnet and all clients default gateways are pointed towards the router interface . Maybe you can post what you have .

[pjgordon64]

I don't have an ip address set on the switch. I don't think it is necessary unless I want to telnet into it. Is it?

The topology is two routers connected by a serial cable. An ethernet cable on either router is connected to a switch. Each switch also has a host on it. On one end, I can ping the ethernet interface. When I change the switch that each ethernet cable is connected to, and make the appropriate changes in ip and subnet masks, the same ethernet interface works, and the same one still has the problems listed above, so I don't think it has to do with addressing or subnet masking issues.

[glen.grant]

Saw something similar to this recently where we had cdp one way , seems like it was on a 2600 also , what I did that seemed to fix it was I did "clear interface x/x . Was running cdp debug and I watched it start working so this may be something to try , almost think I saw a bug that related to something like this also .

[cro9uk]

I take it you have checked encapsulation at both ends and the subnets and masks are ok. If so i had a similar problem on my 3640. The interface was up up and pinging the interface from IOS gave me 100% success, however there was no data flow. Turned out to be a hardware failure on the card. Try pinging the interface from the switch, that will tell you if the card is ok. If you have no joy then first replace the cat5 lead (from switch to router) and try again. if all else fails then it could be a hardware failure on the card.

[pjgordon64]

No, I can't ping the router from the switch. I have tried switching the cables with the working ethernet interface and it doesn't help. The ip addresses and subnets are correct.

I hoping against hope that there is another explaination other than hardward failuer.

Thanks for the response.

Paul

[Richard Burts]

The encapsulation failure message is generated because the router does not have a MAC address corresponding to the destination IP address. You might try running debug for arp and see if it sheds any light.

You comment that show cdp neighbors does not show any neighbors. Assuming that CDP has not been disabled on the router and the switch, I think this is another indicator of the problem.

My first step would be to look for physical layer problems, check the cables (or perhaps test with a different cable). If you unplug the cable from the switch, do you get an error on the router? And if you unplug from the router do you get an error on the switch?

Are you sure that the speed of the interface matches on both ends of the connection? It might be helpful if you could post the output of show interface and show port.

HTH

Rick

[pjgordon64]

This is what debug arp gives when I try to ping the host from the router:

2d19h: IP ARP: creating incomplete entry for IP address: 192.168.55.10 interface

FastEthernet0/0

2d19h: IP ARP: sent req src 192.168.55.8 0009.b77c.0420,

dst 192.168.55.10 0000.0000.0000 FastEthernet0/0.

I don't know if I already mentioned this, but if I create a static mapping the ping still fails.

cdp is enabled on both router and switch.

I've tried different cables, different ports of the switch.

If I unplug the cable from the switch, the protocol changes to down.

Here is show int for the ethernet port:

FastEthernet0/0 is up, line protocol is down

Hardware is AmdFE, address is 0009.b77c.0420 (bia 0009.b77c.0420)

Internet address is 192.168.55.8/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Auto-duplex, Auto Speed, 100BaseTX/FX

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

Last input 2d19h, output never, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

28791 packets output, 2754853 bytes, 0 underruns

0 output errors, 0 collisions, 24297 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Here is sh port:

Secure Port MaxSecureAddr CurrentAddr SecurityViolation Security Action

(Count) (Count) (Count)

-------------------------------------------------------------------------------

It is an empty table.

Paul

[Richard Burts]

When I asked about show port I was thinking generically about Catalyst switch and forgot that you had said that it was a 2950. So what I should ask for is the show interface on the switch for where the router is connected not a show port.

In the show command that you included it shows the Ethernet interface as:

FastEthernet0/0 is up, line protocol is down

It is significant that the line protocol is down. This will prevent communication. What is the state of the other end of the connection?

HTH

Rick

[pjgordon64]

Oh, the down on the protocol was because I still had the cable out -- you asked something about if there was an error message when I removed the cable from the switch. It is normally up and up. Here is the correct output:

FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0009.b77c.0420 (bia 0009.b77c.0420)

Internet address is 192.168.55.8/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Half-duplex, 100Mb/s, 100BaseTX/FX

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

Last input 2d21h, output never, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

29636 packets output, 2836266 bytes, 0 underruns

0 output errors, 0 collisions, 25006 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Here is the show interfaces for the port connected to the router:

Hardware is Fast Ethernet, address is 0009.b702.c6ce (bia 0009.b702.c6ce)

MTU 1500 bytes, BW 100000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Half-duplex, 100Mb/s

input flow-control is off, output flow-control is off

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

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

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

1 packets input, 64 bytes, 0 no buffer

Received 0 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

5323 packets output, 450099 bytes, 0 underruns

0 output errors, 0 collisions, 2 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

I wonder why they are at half-duplex. Aren't both interfaces (2600 and 2950) full-duplex capable. The interfaces are all set to auto.

The other thing is that on the switch there is this line:

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

and on the router there is this:

Last input 2d21h, output never, output hang never

It definately appears they are not communicating.

Paul

[Kevin Dorrell]

Paul,

Just a few of things to check:

1. Are both of the switch ports switchport mode access?

2. Are both of the switch ports in the same VLAN switchport access vlan n?

3. (optional) Is CDP actually enabled on both switch ports, router interface, and globally? cdp enable

Kevin Dorrell

Luxembourg

[pjgordon64]

1. Yes, both switch ports are in switchport access mode.

2. All switch ports are part of the same vlan.

3. Cdp is enabled globally and on the switch ports and router interface

Paul

[netadmin]

Even though both 2600 and 2950 are full duplex capable, every now so often I have run into mismatches or half/full issues on auto setting. A cleaner fix is to lock both ends to 100/full and you will see better communication.

Also, it may have already been mentioned but the switch has to have an ip address if you wish to ping from the switch.