Network Design opinion 1

[fledder]

Our LAN consists of about 125 devices located all on 1 floor. We have no wiring closets. All cat5 cabling comes into our main computer room where our racks and servers are located. We have about 8 or 9 Cisco 2950 switches stacked on top of each other. We have declared one of the 2950 switches as our core switch. It has all our servers plugged into it as well as having all the other 2950 switches uplinked into it. All swtiches are pretty much default. All have the default mgmt vlan and that is it for vlans. No portfast or etherchannel being used. Spanning Tree is still enabled on all switches. We have a Cisco 3600 router for WAN connectivity to remote sites. That router is also plugged into our core switch. I am not really noticing any network problems. I just wanted to get some opinions and ideas on ways to possibly make this a better network. Is spanning tree even needed in our setup since their are no redundant paths? Should I start using portfast on switch ports for PC's and maybe use etherchannel for uplinking the switches. I am stuck with this equipment for now, so I must make use of what we got. 48 port Layer 3 switches with gigabit uplink would be nice, but I can't get that now.

Thanks for any ideas that you can provide.

 

[KiscoKid]

I admit I cringed when I read your post as it sounds like the very first network I ever worked on. Back then though we had hubs and we had regular, problematic network problems. Albeit I did have in excess of 2000 nodes to look after and your base is considerably smaller.

Your network is probably satisfactory to be honest. However it's far from scalable but you could dramatically improve that by perhaps purchasing a pair of 3560 or 3750 switches to be your core switches isntead and relegate the 2950's to access switches only, i.e. to provide user connections only.

I would keep spanning tree enabled. A simple miswiring, i.e. introducing a 2nd uplink to the same switch could wreak havoc for you.

As and when you are in a position to purchase some Layer 3 switches for your distrbution/core, I would entertain allocating vlans to introduce some segmentation.

Portfast on any PC links is always a good idea. Enable BPDU Guard just in case if you deploy this.

You only need Etherchannel if you are considering 200mb+ connections between each switch. I would envisage that with a user base of 100+, you would be hard pushed to load up any uplink to over 100mb but if you find that's happening, then yes Etherchannel is the way forward.

This core 2950 switch you talk about that terminates all the server connections, have you configured it so that it is root switch? I would recommend you control the root switch election for optimal performance.

 

[PalmTest]

Hi Fledder,

It seems to me that the physical part is O.K.
(If it works, don't fix it)

I would however enable Portfast for the Workstations and Servers.
If PortFast is not enabled for the Workstations (with Windows XP I guess) might have difficulties when using DHCP at Bootup, because the switchport is still figuring out if a Switch is attached to it. While the Switch is thinking about this, no traffic can flow through the switchport and a DHCP timeout might occur.

I would also use Trunks between the Switches.
This will come in handy when using VLAN's.

Leave SpanningTree as it is.
If you accidentally patch two Access Switches together, Spanning Tree will protect you.
(But I guess that you are the only person who performs patching)

Do you use Syslogging?
Find a (free) Syslog Server on the Internet, instal it on your Management Workstation.
Enable Syslogging on all the Switches, so you are informed when a switch has something interesting to report.

Do you have a spare PC? You might consider to use MRTG (GNU GPL)to monitor all the ports on your CoreSwitch.
This way you might see utilization fluctuations you never expected.
Get a complete MRTG bundle at

http://www.openinnovations.com/mrtgbundle.html

Scroll down to download the MRTG2 bundle.
(This is a good moment to change the default SNMP community strings on all the switches)

Perhaps other Forum readers have more Hints&Tips.

 

[fledder]

Thanks KiscoKid. I took a look at the spanningtree config on all the switches and it just so happens that our core 2950 switch has the lowest mac address and it is our root. If I can get the new switch approved, it will be a layer 3 for sure.

Computer Running Slow

http://www.computerrunningslow.com

 

[fledder]

Thanks PalmTest,

I will look for a free Syslog Server...great idea. I will also explore the free port monitoring software

Computer Running Slow

http://www.computerrunningslow.com

 

[jdeisenm]

Here are some settings I would put on your "access ports".

interface FastEthernet0/1
switchport access vlan 1
switchport mode access
no cdp enable
spanning-tree portfast

For routine maintence, in addition to checking bandwidth on your uplinks, make sure your interfaces are running full duplex. Also, check for errors and collisions...Especially after server crashes and reboots.