Cisco Switch Config Review

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Carlosinfl

Loves the juice
Joined
Sep 25, 2002
Messages
6,633
I've got a server that is timing out and is very slow. When I view the port on the switch that the server's plugged into, I see that the port has many errors / collisions. I also noticed it's running at half duplex as well:

Code: 
GigabitEthernet0/11 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 001b.54c6.ee0b (bia 001b.54c6.ee0b)
  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)
  [B][COLOR="Yellow"]Half-duplex, 100Mb/s, media type is 10/100/1000BaseTX[/COLOR][/B]
  input flow-control is off, output flow-control is unsupported
  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: 1331911
  Queueing strategy: fifo
  Output queue: 0/0 (size/max)
  5 minute input rate 81000 bits/sec, 39 packets/sec
  5 minute output rate 509000 bits/sec, 50 packets/sec
     667083406 packets input, 54365047130 bytes, 0 no buffer
     Received 428 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     896036917 packets output, 564804192781 bytes, 0 underruns
     0 output errors, [B][COLOR="Yellow"]20511126 collisions[/COLOR][/B], 1 interface resets
     0 babbles, 30531440 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

My server, switch, and Firewall all have Gigabit connections so I wanted to know if you guys recommend I manually configure this interface to run at Full Duplex of should I leave it alone?
 
If they are all gigabit, you should be getting a full-duplex gigabit connection. With a known-working gigabit laptop or computer, try connecting to each of the components and finding out where you are not getting a gigabit connection.
 
I configured the port in question to run at full duplex and the line stayed up and worked fine. Then when I set the speed to 1000 on that interface, the line went down and I lost the link light notification on that port. I can't understand why a port on my gigabit switch 0/11 to my ASA 5520 Firewall would die when set to 1000 Mbps. I verified that my ASA has 1000 Mbps connections so I can't see why that would fail. Same thing happens on the ASA interface as well...

Code: 
bishop# show interface dmz           
Interface GigabitEthernet0/2 "dmz", is up, line protocol is up
  Hardware is i82546GB rev03, BW 1000 Mbps, DLY 10 usec
	Full-Duplex(Full-duplex), [B][COLOR="Yellow"]100 Mbps(100 Mbps)[/COLOR][/B]
	Input flow control is unsupported, output flow control is unsupported

Any ideas why that would fail when both the switch & ASA both are capable of 1000 Mpbs?
 
how long is the cable?

Try a new one if its a patch or get a validating cable tester than can show you noise, capable link speed, etc.
 
schnell said:
how long is the cable?

Try a new one if its a patch or get a validating cable tester than can show you noise, capable link speed, etc.
Click to expand...

Going from the Firewall (ASA 5520) to the Cisco switch it's 5 ft. I replaced the cable with a newly tested Cat6 Ethernet cable. It auto defaults to 1/2 duplex & 100 Mpbs for some strange reason & doesn't mind being forced to 'full duplex' but the connection drops when I manually change the speed to 1000.
 
there is a bad port on one side if you are losing link when you try to force speed 1000
 
If you set the speed to 1000 on the switch, then you have to set it to 1000 on the ASA also. Otherwise it won't be able to negotiate and it will fail. You could set both of them to auto also. From what I can tell, your switch is now set to full duplex with 1000 speed, and your ASA is set to full duplex 100 speed.
 
I'm not a Cisco guy so to configure a specific interface to be auto would simply be:

Code: 
speed auto

Is that correct?
 
Carlosinfl said:
I'm not a Cisco guy so to configure a specific interface to be auto would simply be:

Code: 
speed auto

Is that correct?
Click to expand...

Correct. You want to do:
Code: 
speed auto
duplex auto

or
Code: 
speed 1000
duplex 1000

on both devices interfaces.
 
it sounds like a bad port, can you plug in your ASA into a different gigabit port see if it works then?
 
The spec for 1000Base-T (gigabit Ethernet) includes a reliable auto-negotiate mechanism. This was not true for 10/100. So if you have auto/auto setup on both sides, and it's coming up half-duplex, that means the 'test' is failing. It could be a bad pair, bad cable, bad interface, etc. I would *not* force 1000/Full if it is not negotiating correctly.
 
I configured both the ASA 5520 (Firewall) and my DMZ switch to both operate at 'auto' for duplex and speed & everything worked perfect. If I configured the Firewall to run at auto but didn't configure the switch, I would lose connectivity until I did so on the DMZ switch. Now everyone is running at 1000 Mbps as expected.

Thank you!
 
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