Help with 2216

Question

Hello!

I need some assistance in configuring/understanding the 2216 switch.

Here is my setup. 5 Dell Optiplex (Out of the box) desktops running XP Pro (brand new machines about 1 month old). PowerEdge1800 server (brand new, 1.5 month old but OS has been rebuilt from scratch) running MS Small Business Server 2003. All 5 desktop are connected to the server via the 2216 switch. The server serves IP address to the desktops (local private IP via DHCP).

I have Goldmine 6.x (5 user pack) installed on the server and is accessed by the 5 users. To enhance Goldmine performance, I decided to modify the network setup after having gone through other options such as software settings, etc.

I modified the NIC settings on the desktops to change from 'AutoDetect' to '100FD'. The settings for the NIC on the server was also modified from 'AutoDetect' to '100FD'. I thought this would help eliminate some of the negotiation traffic and improve speed of access. It turned out that it had the opposite effect. The performance and access speeds were degraded significantly.

The good news is that I reverted back to 'AutoDetect' on the desktops and server and the users have laid down their arms. I need some help in understanding why this happened and how I could fix it to improve network access speeds. Thanks.

Cheers
Subbarayudu

HiTechRedneck · Answer

Are any other devices on this sub-net (router, bridge, etc)?  Does the server have only 1 nic?  Are you using mapped drives between the desktops, for other 'sharing'?

sdarisi · Answer

Are any other devices on this sub-net (router, bridge, etc)?
No, there are no other devices on this sub-net!

Does the server have only 1 nic?
Yes, there is only one NIC in the server

Are you using mapped drives between the desktops, for other "sharing"?
There is no sharing of folders between desktops. There is one shared folder on the server that is accessible to all desktops.

HiTechRedneck · Answer

OK. That is good news.  The DHCP service provided by your server, how long have you set the IP lease for?

GregG1 · Answer

Sdarisi,

If you are asking why you saw degraded network performance when hard-setting the NICs to 100full, this has nothing to do with DHCP or other network devices. This is a standard problem caused by a negotiation mismatch. The 2216 is an unmanaged switch, therefore all ports use Auto-Negotiation to determine link speed/duplex. Valid negotiation settings require either auto-negotiation on both sides or hard-set speed/duplex on both sides. If one side of the link is using auto-negotiation and the other side is hard-set, you will get a duplex mismatch and the link will be established at half-duplex.

Auto-negotiation works by determining the best speed/duplex supported by both devices. If the NIC and switch both support 100full, the link should be established at 100full. It works at an electrical level so there is no network traffic utilized.

sdarisi · Answer

Greg,

Thank your for your detailed note and explanation. This is indeed what has been done. All machines on both sides of the switch are configured for 100FD to eliminate any overhead associated with negotiation. Despite this configuration, I was surprised to see the performance degradation (lower than when neogotiation took place on the network).

HiTechRedneck, as for your question, the DHCP lease is set at 8. Hope this helps.

Please advise any suggestions/options that I can explore. Thanks.

Cheers
Subbarayudu

GregG1 · Answer

Auto-negotiation of link speed/duplex is performed between the NIC on the client and the port on the switch. It has nothing to do with how the speed/duplex is configured between two clients (unless the two client NICs are connected directly using a crossover cable.   Since the switch is only capable of auto-negotiation, the client NICs must be configured as auto for valid negotiation and full-duplex connectivity.

sdarisi · Answer

Hi Greg,

I am sorry if I am creating confusion. Please allow me to elaborate.

All the 5 dekstops are connected directly to the switch through their NICs. The server is also connected directly to the switch. ie. all connectivity in the network takes place through the switch

FYI, the firewall that connects to the internet is also connected to the switch.

I manually configured the NIC on desktops and server to 100FD and noticed a significant performance degradation (in regards to network speed/performance as measured by access from desktop to server, network logins, file transfers between desktop and server or desktop and desktop, access to shared applications located on the server, etc). This was surprising to me as I had eliminated the (small) negotiation overhead associated with the auto-sensing option on the individual NICs. I have since reverted back to the auto-sensing mode on all devices.

Hope this provides clarity. Thanks.

Cheers
Subbarayudu

Networking General

Help with 2216

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