Helping a Friend - Slow Network with Switch Added

[Fatawan]

Here is the description I got this evening from my friend. They have Ethernet cable to each room of their house, home-runned to a switch in the basement(16 port). They have Comcast Business 150meg service. He works from home with three devices in his office. It sounds like they have a combo modem/router from Comcast. There are two older Apple wireless AP's connected to the switch also. He gets 180meg speeds when his three office lines are connected directly into the router/modem(it has 4 ports). However, if you connect the switch to the router, service slows to a crawl. If his office lines go through the switch, it is super slow again. Only when his lines are directly connected to the router AND the switch is NOT connected to the router does he get full speed service. They have changed the router/modem and tried 3 different switches. Same results. I told him to connect it as he has it now(office lines into router, no switch) and run speedtest. Then connect switch, run speedtest. Then I told him to start with one AP and disconnect it from the switch, run speedtest. Then connect the other AP and repeat. If no change, start disconnecting one at a time and repeating speedtest. Any other ideas as to what could be going on?
Thanks!

 

[degrub]

Without specific details, we cannot help you much.
Are the switches used all gigabit full duplex ?
If they were 100 mbit port speed that could explain it.
So would a bad cable between the switch and the router. Or a bad port. Or a bad network port on a device.
A network layout sketch would help, with specific make and model of all devices attached.

Btw, i would test by removing all device connections and add back one by one, testing each by itself , then adding together.

Pingplotter might help you figure out which device is slowing it down.

 

[Fatawan]

Thanks for the reply--I do recall him saying that it was a gigabit switch, as were the others they tried. I will let them know on your advice and post what happens.

 

[thiggins]

Disconnect all devices that do not support Gigabit Ethernet and see if that helps.

https://www.smallnetbuilder.com/lanwan/lanwan-features/30212-when-flow-control-is-not-a-good-thing

 

[Klueless]

I really liked the Mr. "thiggins" response (once I got used the idea of 100 mbps as slow).

Since everything was working fine on the router it would seem that you should get good performance by moving gigabit to the switch and leaving all non-gigabit on the router?

 

[Fatawan]

UPDATE: They didn't do anything in the interim, so I finally went over there today.

They have a Comcast for business modem hooked to the Comcast for business router. The house was wired 15-20 years ago with Cat 5 to a patch panel. There is Cat 6 cable from the patch panel to a 16 port gigabit switch. The lines attached to the switch included an older Apple AirPort Extreme, AirPort Express, and Time Capsule as well as unused Ethernet sockets. The router itself had 3 office computers and an Airport Extreme plugged in to the Ethernet sockets.

When the office PC's are connected directly to the router, we got 175mbps speeds. If I disconnected everything from the switch and hooked up only the router to the switch and then added a single PC via Ethernet directly to the switch, I got 89mbps(that pc was getting 175 when direct to router). If I then added the office PC's to the switch, I got the same 175 mbps as previously.

I then started adding back lines to the switch and testing. All the PCs, whether in the office or directly connected, tested at around 80-89mbps. Finally, we connected an Airport Extreme that was new in December that provides coverage to their basement to the switch. That's when it all came crashing down. It is set up in bridge mode. All the PCs lost connectivity after that. However, if we plug the office PCs and the offending Airport Extreme directly into the router, everything works, including WiFi on the Airport Extreme. If you add the switch at that point, it all comes crashing down.

Another bit of info--this whole setup, with the AP's and router and switch, was working perfectly for months until there was a surge or somesuch that fried the Comcast router. That was replaced, and the original setup has not worked correctly since. So, what say ye now?

 

[degrub]

i bet switch
or switch power supply.
Go get a cheap gigabit unmanaged switch 8 port and test.

 

[thiggins]

So, what say ye now?

I say use some paragraph breaks so I don't have to struggle to read your post.

 

[Fatawan]

i bet switch
or switch power supply.
Go get a cheap gigabit unmanaged switch 8 port and test.

The switch has been swapped out for 2 different switches--no change.

 

[Fatawan]

I say use some paragraph breaks so I don't have to struggle to read your post.

Done

 

[Fatawan]

I am having them swap out the other Airport Extreme they are using for the one in the basement and see if the same results occur.

 

[degrub]

i don't understand this statement -
"If I disconnected everything from the switch and hooked up only the router to the switch and then added a single PC via Ethernet directly to the switch, I got 89mbps(that pc was getting 175 when direct to router). If I then added the office PC's to the switch, I got the same 175 mbps as previously."

it sounds contradictory.

Are you saying that with one PC on the switch the speed was 89 but adding more PCs increased each PCs speed to 175 ?

Or are you saying this is a different PC from the office PCs ?

What were you doing with the cables and ports when you did this ?
almost sounds like a bad cable or cable termination.

 

[Fatawan]

I went back and pulled out the two older (non-gigabit) Apple routers and now there are no issues. I am not sure what type of interaction was happening between the apple products and switch that caused an internet disconnect, but it was resolved by removing two of them. Thanks again for the help.

 

[sfx2000]

One thing to consider with Airports - if just using them as AP's and not as routers, ensure that they're configured in "Bridge Mode" as that's what Apple calls it in the Airport Utility.

If configured as a router, and nothing on the WAN side, and plugged into the LAN port of the AP, one can get into some interesting issues... including, but not limited to ARP storms and some unexpected spanning tree issues.