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Switch Problem?? Slow LAN Communication

So I put this in the wrong forum I believe, so I'm putting it here in the small business support forums - hopefully this is the right place...

Firewall: Cisco SA540

Switch: Cisco SG 200-50

Router (DHCP): Wireless-N Gigabit Security Router WRVS4400N

So I work for a small veteran owned company, about 10 employees on site at any given time.

I was tasked with restructuring the IT infrastructure, and bringing it up to date.  I decided to go with gigabit hardware, and rewired with cat6 cable throughout our office - so that's all in place.

I want to make sure though that I have the proper setup for what we have.

This is our general set up line:

T1 Line -> Adtran Router (provided by service provider) -> Cisco Firewall -> Cisco Wireless Router (acts as the DHCP) -> Cisco smart Switch -> Out to the offices...

Originally our router and firewall both shared the same gateway of the Adtran router - when I purchased the new equipment, I wasn't able to do that (I'm guessing that the firewall was letting the router communicate directly with the adtran router outside of the firewall).  So I set the Cisco Firewall's gateway as the Adtran Router, and I set the Cisco Wireless Router (DHCP)'s gateway to the Cisco Firewall's internal IP address.  The Cisco Firewall interal IP is set to and the Cisco Wireless Router (DHCP) is set to and then all of the internal machines are on the

The only problem I've been running into with this set up are machines talking to each other, such as accessing our server, or accessing the network printers... There is a great communication delay in doing this - so I'm trying to find out if I have this all set up generally correctly.

I have a sneaky feeling that the switch is deferring to the router (DHCP) to route the packages within the LAN, rather than keeping it within the switch.  When someone goes to Print, it shouldn't have to go through the router, it should stay at the Switch level - but when people go to Print on our machine, it usually takes awhile to FIND the printer, and then sometimes it times out when sending files.  We usually send very large documents to our Xerox printer, and we print all day so this is delaying a lot of our production...

Please ask if I'm not being clear, or if I can provide any logs or answers to anything?

Thank you!

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Switch Problem?? Slow LAN Communication

I'll continue trying to post information until I come up with a solution, or until someone can help me troubleshoot this.

I just don't know if I have this set up incorrectly, or if there's a problem...

I checked the ARP table for both our DHCP/Router and for the Switch - the machines that people are struggling connecting to are not on either table.  I also checked the dynamic MAC address table on the switch - and they're not on their either...

Now - These machines (Printers/Server) are on a static IP address - so I'm guessing I should add them to the MAC address table on the switch?

People are able to print, but it's slow - And when they select the xerox to print to, it takes about 10-15 seconds to connect to it (used to be pretty instant on the old hardware), and if someone is sending a large file to print, it will either crash the software or the printing job will timeout.

Same with the server when it comes to transferring large files - it will timeout and stop transferring..

And as I write this, I wonder if there is a setting somewhere that allows a maximum file size to be transferred across the switch...

Is there a way, once I set the printer/server as static addresses on the corresponding ports, to set a higher transfer limit on those ports?


Re: Switch Problem?? Slow LAN Communication

Hello RJ,

This is the correct place for your devices.

Are all devices on your network connected directly to the switch? Also you mention the connection goes SA540 -> WRVS4400N -> SG200, are the firewall and router going from LAN to WAN?

You are correct about all the traffic being local and should only be going over the switch. If you do a tracert to your server or printer, it should only have one hope straight to the device and should give you an idea if it is going over the router.

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Switch Problem?? Slow LAN Communication

So our network goes like this...

T1 comes into the building, and it's wired to our Adtran router (provided by our service provider) - one cable goes from the adtran router to our SA540 firewall.  Then one cable goes from our SA540 firewall to our WRVS4400N DHCP.  Then one wire goes from our WRVS4400N DHCP to our SG200-50 Switch.  Then everything else is connected directly into the switch. 

The SA540 firewall's gateway is set up as the Adtran router, and it has an exterior static IP address.  It then has it's own internal IP address.  That internal IP address is then set as the WRVS4400N DHCP's gateway, and that DHCP has a different internal IP address - one is on the and the other is on the

Tee WRVS4400N was obviously a wireless router, which I have since disabled - as I was concerned that people connecting wirelessly to the DHCP router were bypassing the switch all together.  So I disabled the wireless feature, and added a wireless access point that is connected directly to the switch.  So every packet, coming through the wireless access point, must pass through the switch.  I would prefer to use the WRVS4400N for wireless acces, but it was one piece of troubleshooting I could do.

Yes - when I do a tracert on any of our hardware it is an immediate hop to the device, and does not pass through our router.

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Switch Problem?? Slow LAN Communication

by the way...

we do not have any problems at all connecting to the internet - so that setup between the firewall/router seems to be right??

We're having a lot of communication problems between machines internally...

Another one that has developed is we have two users on quickbooks that reside on one of the accounting machines - and the only way the other accountant can work on it is to connect to the file on the other machine - both are hard wired, but after working for a bit, the connection is lost between the two, and crashes the program they're working on...

Now both of these machines are set up with dynamic IPs - so my secondary thought that this is just because the static IPs are not in the switch doesn't seem to be the reason.

I feel like there's an overload going on somewhere, and the Switch is shutting the connection down?? And then having trouble connecting to the server (which has a static IP address), may be because the IP address can't be found anywhere in our Switch or Router


Switch Problem?? Slow LAN Communication

From the layout there should not be any problem from the WAN side of your network.

In the WRVS4400N under Status > Local Network you should see the server IP and MAC address. Also, under the dynamic MAC address table for the switch, do you see entries being learned for other devices?

Knowing that it is local traffic only, I would suggest making sure the switch is on the latest firmware. You could also do a packet capture to see what kind of traffic is going around on your network. From the information you have provided, I would start looking at the amount of traffic on your network and to make sure that one system is not sending alot of network traffic.

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Switch Problem?? Slow LAN Communication

Thanks again for responding Robert

I checked to make sure all of our firmware is updated and it's good to go there.

When I look at the WRVS4400N Status > Local Network - none of the machines on my network that have static IPs are listed... neither my server, nor my printers are listed there.  They are not listed under the ARP table either.

In the Switch - Under dynamic MAC address table I do see entries being learned for other devices on our network. 

I also reset all of the port statistics, and then waited for about a minute - and went through to look at packets received/transmitted on all active ports - no port showed any outstanding transmission/receiving that exceeded about the average of the other ports - so it doesn't seem to me that anything is flooding the system at first glance.

I'm not sure if there is a better way to capture these statistics. As I mentioned, one of the thing that concerns me is that our devices with static IP addresses are not located anywhere, in any of the tables.  In the switch, I did go ahead and add the static devices to the MAC table for their respective ports - but still nothing on the routers network table nor ARP table.

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Switch Problem?? Slow LAN Communication

One other quick thing - is there anywhere that I can look for a setting that sets a maximum packet size or transmission size per port? or overall?  I've noticed one thing with our server, is when we attempt to move a larger file (around 50mb or so) off of the server and onto a local machine, the server is disconnected and we have to log back into it.

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Switch Problem?? Slow LAN Communication

And also - lol - sorry...

For the DNS on these internal machines (DHCP, Switch, Printers) what should they be set as?? the DNS for my firewall is set to what looks like an external server, but the DNS for the printer here is set to the internal address of the router DHCP, and the router DHCP's DNS is set to the same as the firewall's... does this matter since we aren't having any problems with the internet?


Switch Problem?? Slow LAN Communication

DNS should not be causing a problem. If you are able to get to websites by name then everything is working correctly. If you are intrested in trying it, there is an option for Jumbo Frames. It is located under Port Management > Port Settings.

Try setting that and see if you still have problems moving large files.

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Switch Problem?? Slow LAN Communication

I'll give the Jumbo Frames a go and see what we come up with.  Is there any reason why the MAC/IP Addresses would not be coming up in any tables in the router nor switch?

I'm just getting the feeling that because it's not in the table, it's broadcasting to all ports until it finds it, and that's what's causing the hold up.

Do you know of any settings anywhere that put a time limit on how long a connection lasts between two machines? For instance, when one of our accountants accesses another's machine to work on a QB file, that connection gets terminated after some time.  I would like to open up the time limit between their ports or at least mac addresses, or something so that it stays open for a longer period of time, or something.

Thank you again for all of your help!


Switch Problem?? Slow LAN Communication

The switch will learn the MAC address of devices that send traffic through it. And what you said may very well be true for the entire network. Each time they are looking to send traffic to the server they would send out an ARP request. You could try a different port for the server, but there might be more going on then just the connection. For that I would recommend capturing the packets of the server just to make sure everything is showing up correctly.

As for a connection time out, there would not be anything like that on the switch by default. As long as there is data to be sent, the switch will send it along.

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