Fine tuning a network

[HodgeHi]

Hello all,

 

So the half-term is coming soon. during this week i want to look at the network and tweak it's configuration a little since it seems to be quite slow, especially when using OS X over the network, just browsing the Internet brings up the spinning ball for a second or two.

 

So my question is how's the best way to tune a network? What tools would be best used to do this job?

 

We have a few SRW-2048 switches which allow for quality of service configuration although I'm not too sure just as to how this works.

 

I am also looking at teaming up the connections on some of the servers.

 

One other thing i need to look at is setting up DNS to utilise DNS round-robin. My AD servers have DNS installed. Is round-robin configured automatically?

 

Also the main DC seems to be used for nearly all connections, authentication, DNS etc. How can i get the 2nd DC to be utilised more?

 

Also is it wise to do this stuff without any users in or should i do it when there us traffic flowing across the network?

 

Hope you can help

 

Thanks

[SYNACK]

Network tuning can get quite complicated. Personally if I was planning on doing something like this I would be checking the loading on the live network while it is in use using something like performance moniter on windows servers and other tools like SNMP moniters depending on what hardware you have to see if there are any bandwidth or queue bottlenecks. PRTG Network Monitor - intuitive network monitoring software or How-To: Measure your bandwidth with SNMP -- Engadget

 

I would then look at using something like the wireshark network sniffer to see what kind of network traffic is flowing over the network.

 

As you mentioned the Macs I would use a wireshark trace on one while it was having the issue to see where it hung up and look to speed up that service, probably DNS (which you can make more aggressive).

 

Most of this stuff apart from the mac network trace would be better done on a live network but given the extra cpu cycles to moniter it all may slow it down further.

 

I would also suggest posting a good network diagram here or doing one and going over it to look for any possible weak points. You can simulate traffic but it is not as good as the real thing.

 

 

Edit: to make DNS hit the other server first change the DNS server order in the DHCP service config.

[HodgeHi]

Thanks for the info. I have wanted to look at SNMP but didn't quite understand how it worked.

 

I think i may need to investigate SNMP further.

[DMcCoy]

Are you redirecting the cache to the local HDD on the Macs? They can be very slow loading Safari when all the files are on the network as it opens an awful lot of them.

[Linfit]

Wireshark is a good place to start. If you use it to monitor your network in normal operation it will give you a good insight into what is happening and what devices are generating traffic.

 

Once you've looked at the captures you will probably find a fair bit of broadcast chatter that you can find ways to turn off. Network printers are notorious for this; they might have manufacturer specific protocols, IPX and all sorts of other redundant rubbish that can be simply turned off. Once you get a better feel for the normal traffic you will start to see potential issues that you can get into more deeply.

[HodgeHi]

Are you redirecting the cache to the local HDD on the Macs? They can be very slow loading Safari when all the files are on the network as it opens an awful lot of them.

 

I had. I followed your post on a previous thread about re-directing a few locations (Application Support, log, printers etc). I had a few issues with some of the re-directs however. iWork 09, Pages in particular) kept crashing after printing a document. Upon creating the Printer folder again the problem went away.

 

Also some of the re-directs didn't seem to take on login and iWeb failed to load correctly since it could not create it's site file in the Application Support folder.

 

I think that i kept the caches and logs re-directs though. I will check this.

[HodgeHi]

Wireshark is a good place to start. If you use it to monitor your network in normal operation it will give you a good insight into what is happening and what devices are generating traffic.

 

Once you've looked at the captures you will probably find a fair bit of broadcast chatter that you can find ways to turn off. Network printers are notorious for this; they might have manufacturer specific protocols, IPX and all sorts of other redundant rubbish that can be simply turned off. Once you get a better feel for the normal traffic you will start to see potential issues that you can get into more deeply.

 

We do have a fair number of Networked printers now. I will have a look at their configurations. These haven't been looked at since they were installed.

[p858snake]

Perhaps do a map of your network in something like visio/dia showing how everything connects together and all the devices on it, and look to see if theres anything that can be done physically.

[bio]

I would use cacti (Cacti: The Complete RRDTool-based Graphing Solution) and wireshark to troubleshoot this one

 

bio..

[HodgeHi]

Perhaps do a map of your network in something like visio/dia showing how everything connects together and all the devices on it, and look to see if theres anything that can be done physically.

 

In what way would i move connections around to optimise network traffic. At the moment i have 5 switches each daisy-chained through ports 24 and 48. I have recently connected the bottom switch to the top switch for fault tolerance.

 

Is this the best method?

 

Also the network wiring and switches are cat 6 which i use to connect the switches together. They do have connections for fibre but i haven't used these.

[_Adam_]

Concerning your switches I am not familiar with the SRW-2048 options, but if you link all of them together in effectively a circle (or create multiple paths between 2 or more) you will need to ensure spanning tree protocol is used. If not you will have bridged loops which will result in flooding the network and this could result in the slowness you see.

 

As for linking between the switches, it comes down to the amount of traffic your servers/workstations pass. It may pay to create trunks between them with 2 or more links between each switch.