Cabling Switch to Switch to Switch Problem

Hi,
I would like to know what are the standard Uplink Ports on Switch and Hubs. For instance our 1 wiring Closet has 4 Switches and they are all connected to each other twice via straight thru cable(shouldn't it be crossover cable from switch to switch on any port or switch to hub???) and one Switch has a Fiber Module where the Line from the other building is coming thru. No switch are stacked and they are 3com 24 port switches. The Problem is that some ports are 100 Half Duplex and on 2 switches All the Status and Packet Light are Orange on every port.
My theory is that the Switch with the Fiber Module is giving the 3 switches the connection to the Internet/Intranet. All the other switches are just sending broadcast in a loop thats why its 100 Half Duplex on some ports.


-thanks any info can be directed my way via e-mail at Vangandr@cssbh.org

All settings are Auto Negotiate , AutoSense , Flowcontrol=Enable, STP=Disabled, No Rip/Ripv2/OSPF, no QoS, LCAP=Disable, Vlan1=Default Management Vlan,

When connecting switches to switches etc you normally plug a straight thru cable from an uplink port on one to a normal port on another. However, many switches now include the capability to automatically detect if a switch is attached to the port and make an changes to the connections as need. Therefore, with many switches, you can connect them together with straight thru cables plugged into normal ports.

You've connected each switch to another switch with two cables. I've had problems in the past when I've connected switches together twice before - just connect them with the one cable and I think your status and packet lights will stop.

THe switches are newer 3com 17707 , 1000 24 port 10/100. I will try connecting just the 1 switch to other and not having 2 switches go into 1 switch. Looks like this

SW1 port13 ------> SW2 port 13
SW3 Port 24 ------> SW2 Port 24
SW2 Port 7 --------> Fiber Transcevier going to DSL Router

I would say that probably looks better I'd be surprised if you still get the flashing activity lights.

You may want to look at the config as you can load balance these ports (its called fast etherchannel) where you can group two or four ports together and load balance by source or destination. for instance lets say I have a server with a fast etherchannel card with 4 100Mbps ethernet ports I could plug that into the first four ports of the switch put them ports into a port group ( this makes the switch see these ports as one logical port) and I would have 400Mbps to my server. In full duplex 800Mbps. You can also connect switches together this way. On cisco you can make the port groups layer2 or layer 3 port groups. to make it layer3 give the first interface an IP address (which will give it to all interfaces in the group) and type no switchport.

Switches use spanning tree protocol (or should be using) to avoid routing loops so if you plugged 2 switches together on two ports one would actualy be turned off untill the other fails (this is a failover). I am confused why it says STP=dissabled unless that is for the port and not the global.

Also you should have one main switch that your servers plug into and all other switches plug into that one also so your not making multiple hops to get to the servers (if using cat5). If not then use the stacking capabilities (usualy needs special cable and or card) such a Gigastack modules in cisco and stacking interface on back of most bay and 3com switches.

Come to think of it I messed with one of these about 6 months ago and 3com calls port grouping, port aggregation ( I mainly do cisco). when this is setup you have to set speed and duplex manualy on both sides otherwise it will auto negotiate 100 half and usualy has a bunch of deffereds. If I remeber correctly the only way to veiw this and configure on 3com is through the management software that runs on your PC (maybe that was only the Intel switches bah). On the 17707 is this a 3c17707/4000 series switch(does it say 4050 or 4060 or 4070 anywhere)? as these are 10/100/1000 Mbps ports and will be yellow if they are running 10 or 100 Mbps and will be green at 1000Mbps. Also if you have any devices (PCs, Printers or whatever) configured staticly for speed and duplex you have to configure the port speed and duplex you can not let it auto negotiate as well if you have a printer that only has a 10Mb NIC you will need to set the switch speed and duplex also if this is a 4000 series switch then you have to leave it in auto when conecting 1000 to 1000 as manual duplex is not supported.
Basicly if you are not familiar with the switch get the manual and read it before making changes especialy if there is no performance issues at this time and the only issue you have is the yellow lights or have someone set it up that is more familiar with this switch if you are having performance issues as all switches are different in their own way.

If someone did set these ports up for aggregation then you will have to dissable the aggregation before using the other port so be carefull I would not recommend jumping in and moving stuff around at this time.

juniperr- I am a cisco guy also but just got hired in as a Network Administrator to work with 3com Switches. So far it has been judgement day.

Here is all the equipment we have and the physical layout.

5 Wiring Closets Total 1 Across The Street

Central Closet - Problems Lots Orange Packet and Status Orange LED's
Not yet documented only seen 2 Switch and 1 Hub
1 Switch is the 3Com 3c17701 4924 - Switch with lots problem
1 Switch is a 3com 24 port - Everthing ok on this one
Hub is Netgear DS524 - ok here



Center Closet - Problems Lots Orange Packet and Status Orange LED's
Equipment:
-Switch A 3Com Superstack 3 3c17203 Switch 4400 24port
-Switch B 3Com Superstack 3 3c16465B 24port
-Switch C 3Com Linkswitch 1000 3c16900 24port
Physical Layout:
Fiber Transceiver to Rj45 -----> Port 24 on Switch A
Port 23 on Switch A ------> Port 26 on Switch C
Port 1 on Switch A -------> Port 24 on Switch B

2nd Closet - Ok here
Equipment:
-Switch A 3Com Superstack 3 3c16980A Switch 3300
-Hub A Netgear Dual Speed Stackable Hub DS524
Central Closet RJ45 ------> Port 1 Switch A
Central Closet RJ45 ------> Port 24 Hub A

3rd Closet - Everything ok
Equipment:
-Switch A 3Com Superstack II Switch 1000 (POS with Fiber Module Installed)
-Switch B 3Com Superstack II Switch 1000 (POS)
-Router A Linksys Router BEFVP41 Used to go to another room with just 1 Line on port 1
Central Closet Fiber Line 1 -----> FX Module on Switch A
Port 26 on Switch A ------> Port 24 on Switch B
Port 11 on Switch B ------> Wan Port on Router A
Port 1 on Router A -------> PC Host



Any Help would be appreciated. I hate 3com Switch and no good documentations for anything. Seems 3com likes to Add All Models into one datasheet ;(

Seems to be sending a lot of Broadcast ARP. I am using Ethereal and 1-600 are all Broadcast. Im wondering what is causing all these broadcast on my network??

Ok what exactly is the problem you are seeing so far everything you say is normal?
Just so you are aware the 4924 is 10/100/1000 on all ports and if running at 10 or 100 will have yellow lights on it only if it is running at 1000Mbps will it be green. Also it is common in a network of your size to see lots of ARP broadcasts (this is how your PC talks to other PCs on the same network as NICs only know MAC addresses not IP so it will ARP if sending to another machine on the same network to build its ARP table also might see lots of DHCP requests) Actualy whith what I am seeing you may want to start thinking about VLANS at this point. How many users are on this subnet? As I stated before look into your config and see if port aggregation is setup which would be why there is two connection from it to each ajoining switch ( you actualy want this!). also if you know the IP address of your switch use the web browser to connect to it so you have a graphical view.

Couple of comments

Never wire switches in series. You never want to go below three levels deep. Don't connect hubs to switches. Look at the switch port the hub is connected to. I will bet you see lots of errors.

Ideally each switch in each closet would be connected to a uplink in a backbone switch located in common with the servers.

Your configuration has each closet having a top shelf switch with hubs/switches downlinked. I have to assume they terminate in the Central ? closet but your diagram doesn't cover that connection that I can see.

Anytime you can do trunking between switches you want to do so. This doubles the bandwidth of the channel between the switches.

The biggest problem I see with this confirguration was a lack of capacity planning.

For example the Central closet has 3 24port switches. At the very least you have two switches going into one. So that is 48 ports going to 2 uplink ports [assuming no trunking]. Not great.

These 3 switches should have been a 72+ port modular switch that also contained gigabit port modules to uplink the remote closets. You would put gigabit cards into the servers and connect the servers to this backbone switch.

The other closets would have their equipment replaced with a single unit with port growth capacity. In other words a closet with 2 24 port switches would be replace with one 72 port switch or at the very least a 48 port switch.

I have been very happy with my Nortel 8010 Passport backbone switch with gigabit fiber blades and a 40 port 10/100 blade. Servers with dual gigabit fiber modules in adapter teams connect to the backbone. 7 Campus switches all connect via gigabit fiber uplinks [all HP's]. Cisco routers connect to the 10/100 blade. Routers connect 9 sites via point to points.

I would suggest you consider upgrading the 3com switches [I heard 3com ended all switch products and support awhile back] and redesigning your configuration from the top down. It is the amount of uplinks you have that I believe are the problem.

Just another opinion. Best of luck!