Slow network problems

Unanswered Question
Feb 18th, 2009

Hi group,

I'm having some slow network issues. We have Catalyst 3560 FastEthernet with IOS version 12.2(35)SE5. We also have a 3560 Gigabit switch. On the LAN, I can copy a file (109 Mb) from an XP PC to our Windows Server 2003 in about a minute, but it takes about 15 minutes to copy that file from the server to the PC. I've tried these same tests with several PCs on the LAN and got the same results. We've even tried the same tests between a PC on another LAN and the server (going across the WAN) with the same results--server to PC, slow; PC to server, fast. On the LAN, I've been able to transfer the same file between two PCs with no problems--fast either way. Now, we've moved the server from the Gigabit switch to the FastEthernet switch and have the same issues--either switch. We've replaced the server cable also--it's plugged directly into the switch. At this point, you may be thinking we have a server problem, but the slow data transfer is only one example. We've had slow printing problems and sporadic network connectivity with some clients. All sporadic, of course. This building was newly refurbished, so the cable is new-- Cat 6. During the data transfers, I'm watching the server performance and there's no memory, processor, or network performance issues. No errors on the switch ports. I've turned off anti-virus on servers and workstations during the transfers. Ports show they're running full/100 and are set to autonegotiate--which again, there's no tx/rx errors. I am going to look at some Microsoft docs, but we keep our MS boxes fully patched and things I've seen thus far talk about this patch and that.

I thought maybe it was a switch configuration problem, as some ports on switches are different than others. Here's an example of how most are configured:

interface FastEthernet0/6

switchport trunk encapsulation dot1q

switchport trunk native vlan 10

switchport mode trunk

switchport voice vlan 172

mls qos trust dscp

spanning-tree portfast

I changed the switchport mode to access instead of trunk and changed 'switchport trunk native vlan 10' to 'switchport access vlan 10', but made no difference. I know a little about trunk vs. access mode, but just a little cloudy. A discussion of tagging frames would be a good post for me for a separate post.

Anyone have any ideas?

I have attached a switch config.

I have this problem too.
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Mohamad Qayoom Wed, 02/18/2009 - 12:00

How is the server's NIC configured? Does it have speed and/or duplex settings hard coded?

Leo Laohoo Wed, 02/18/2009 - 13:35

Good point.

"Now, we've moved the server from the Gigabit switch to the FastEthernet switch and have the same issues--either switch."

When the server was hooked up to a Gig switch, was was the speed and duplex setting of the switch port(s)? Is the server Gig capable? Were there any transmit/receive errors from the switch?

How's the transfer from PC to PC on the same LAN/network or different LAN/network?

christopher_hal... Wed, 02/18/2009 - 13:56

I have just gotten involved, so I don't know if there were any errors on the gig switch. The server is an IBM xSeries and is gig capable. We keep all the switch ports set to auto, but there are some exceptions (routers and some static devices). The one transfer I did from PC 2 PC was different in that one was plugged into the 10/100 switch the other was in the gig switch.

I just re-read you questions...PC to PC on the same LAN is quick--tx & rx. Both ways. That's all I've tested at this point.....but was told that my peers/boss experienced the exact opposite--fast transfer from the server to a pc, but slow from the pc to the server. And also slow from pc to pc. I'll have to re-test some of this myself, so I'm working with known information.


p.j.gerpot Fri, 03/27/2009 - 06:28

We had a similar problem.

There are some bugs known for connecting some type of pc NIC's to cisco switchports.

Changing the duplex,speed and updating de software of the NIC is recommended.

In our case we tried configuring the server with auto flow control on.

that gave good results. Normally it is not necessary to do this buth de network card of that type of vendor(IBM) did not work well with the Cisco switch.

let me know if it worked for you pls


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