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valleytechFlag for United States of America

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managed switch? where to start

i will need to configure a switch of 3COM 4250T to replace a cheapo 50$ network 100Mbps auto-configured switch so that I can look at traffic incoming/outgoing to/from particular router

I have been able to telnet into the switch's built-in console. I also have plugged in the switch for usage
(NET CABLE from ISP) --> 3 COM switch ---> 4 different routers ---> internal servers on each router.

the 3COM switch itself has the capability to auto-negotiate. So far, everything is up. However, I noticed that there are several collisions (light goes yellow = only 10Mpbs).

I'm so blind of **where to start** in order to manage a switch (i was looking at concepts of layer 2 network, but it's quite hard to grasp in a matter short time - 1 week to complete this task):
1. to resolve the collision
2. to look at traffic in detail

any direction will be so helpful

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thanks so much! i was able to access webinterface of the 4250T

Can you please be more specific?
1. assign static IP address/ gateway?
here is my network setup
therefore, the IPs will be at routers? For example, one router is connected at port 10 on the switch (i saw a green indication of 100FD which is fine). I want that router to be public static IP, then i have to set i right at the switch? static IP goes to port 10 for instance.

2. I saw errors right at port 1 where i connect internet cable from ISP to the switch. The port right now is only at 10HD. is there anything wrong?

thanks again!!!
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1. If you can access the switch using the browser it already has an ip address. You may check/change it in Device View, Protocol, IP, Setup. Sorry if I confused you. There is no link with the routers ip addresses.

2. 10HD may be ok if the device attached to the port is an old print server or an old router with an ethernet interface. The important is that they match. I would suggest to log on the router and do a "show interface" (or equivalent) to verify the router side. Worst case, check the lights on the devices to identify the speed/duplex.


10HD shows off at port 25 where i connect the cable provided by my ISP to the switch. The logs only showed number of errors though. they don't say specifically anything the source of the error.

I figured out that there's also 10HD also 10FD are those mean half duplex and full duplex? I manually changed to 100FD and 100HD, the link was down right away. Unless, as you say, the duplex setting should be matched. The switch currently is set to automatically obtain duplex settings.

are those 10HD/FD and 100HD/FD means 10Mbps and 100Mbps?  Besides, the number of erros are 2000 something. may I look into details of those erros?
To answer your question, 10 and 100 mean 10Mbps and 100Mbps respectively.
HD and FD mean Half Duplex and Full Duplex respectively.
Both speed and duplex need to match on both sides (swicth port and server). Very frequently, the "auto" detection does not work very well resulting to a mismatch.
I do not know how to dig more in the errors on the 4250 with using a snmp management tool.

thanks!! look like i will need to check the HD and FD settings. The ISP confirms that the cable should be 10H. however, since there's error, i will need to check up with them again!

in addition, would you mind for another question mark? ;)
since the switch can be automatically set. I succeeded in using MRTG or PRTG to look at traffic in particular ports in the switch. HOw about the other settings like Spanning Tree, Bridge, quality of service?

What can I do with those?general idea will lead to the right direction to dig in deeper!

If you only have one switch/hub, spanning tree (Bridging loops avoidande) can be disabled. Bridge will allow you to manage VLANs (that you are not using).
QoS does not make a lot of sense over the internet (Not "QoS enabled" for now) but if you really want to push it, you may set some queueing in place that will deal with the CoS or DiffServ for the packet bound to your 4 routers. This will assume that something has tagged the packets. Either the source or a router on the path.

Have fun :-)
I will put that switch into action!!