Port Speed Mismatch

[WildMonkey365]

My company installed a hosted voip system for a customer with 10 sites. Our data vendor who sold these jobs for us provided 100Mb managed switches for the Phones and PC network. The router I installed auto negotiates at 1000Mb full. Our systems show the LAN Port going out to the switch is connecting at 100Mb Full as it is a 100Mb switch. Unfortunately the model of router I installed does not have an option to Hard Set the port speed to 100Mb Full. One of our techs suggested putting in a 5 port gigabit dummy switch in between our router and their managed switch. My mai questions are as follows.

1) will the port speed mismatch affect call quality? there is no duplex issue just speed.

2) If putting a switch in between our router and their switch will help shouldnt we be putting in a mangaed switch so we can hard set the port speed on the port connecting to the 100Mb switch? Just putting in a gigabit dummy switch although it would match speeds on the router side would still not on the port connecting to the 100Mb switch correct?

 

[Snipergod87]

Speed mismatches can severely impact data transmission. I have seen one device set to 100 full and another 1000 full but because of the mismatch many packets were dropped and you were limited to 10mbit full.

You dont want to hard set limits on network interfaces unless you can do it on both ends (which it sounds like you cannot on the VOIP router)

 

[WildMonkey365]

That sounds about right. I found a gigabit 5 port managed switch. My thoughts are to connect the router to an auto neg port on this mini switch and hard set a port to 100Mb full and have the data vendor hard set his switchport of the main switch to 100Mb full. Does this sound right to you?

Also if a gigabit dummy switch were to be put in the middle wouldnt there still be a port speed mismatch occurring? Even though the LAN port of router is Auto linked at gigabit the Main switch being 100Mb full would be connecting to a gigabit port that could not be hard set.

 

[Snipergod87]

Does the vendor switch support setting to 100 full or just auto?

You can use the 5 port managed switch to manually specify the interface speeds or let them auto. However since you are getting mismatch issues I would recommend setting the vendor switch and its corresponding switch port on the 5 port device to 100 Full, and your switch + the corresponding switch port on the 5 port device to 1000 full

You will not have any dropped packets this way as everything will be negotiated / set properly

 

[WildMonkey365]

The vendor switch is capable of hard setting port speed to 100mb full but the LAN port on my router only auto senses. My plan is to get this mini managed switch set up with a hard set 100mb full port and get the vendor to hard set his switch port to 100mb full. I will connect the mini switch and the vendor switch together at the hardset 100mb full ports & since my routers LAN port only does auto(1000/100/10) I will leave a port on the mini managed switch (which is gigabit) at Auto and connect to my routers LAN. The port speed from my routers LAN to the vendor switch will be as follows....

Router LAN (Auto 1000mb Full) to Managed Mini (Auto 1000mb Full)
Managed Mini (Hardset 100mb Full) to Vendor Switch (Hardset 100mb Full)

Does this seem like a good game plan? I have to do this for 10 sites.

 

[bill001g]

In general the best option is to leave everything in auto. It is suppose to figure out the speed and duplex. The problems generally come if you try to hard set anything. As soon as you hard set any option it turns off the signalling used for auto detection. The hard coded side does what you have configured it. If the other side is auto it will not get the signalling and most times ends up in half duplex. It will still many times get the speed right but not all the time.

I would hope you manged switch has the ability to set the ports to auto rather than just a fixed rate.

 

[WildMonkey365]

In general the best option is to leave everything in auto. It is suppose to figure out the speed and duplex. The problems generally come if you try to hard set anything. As soon as you hard set any option it turns off the signalling used for auto detection. The hard coded side does what you have configured it. If the other side is auto it will not get the signalling and most times ends up in half duplex. It will still many times get the speed right but not all the time.

I would hope you manged switch has the ability to set the ports to auto rather than just a fixed rate.

Sorry to keep this thread alive. I appreciate your answers. I have one more question. Do you think just throwing a standard gigabit mini switch between the router and 100Mb switch will be fine?The current set up is auto at the router to auto at the switch. The only problem is the router is stepping down to 100Mb because that's the speed of the switch it's connected to. Sorry to drag this out but I really appreciate your answers and it's helping me to look at this at all angles.

 

[Snipergod87]

If i am understanding correctly both are set to auto currently, and they are both negotiating 100Mbit full duplex? If so you don't need any additional hardware. If they are not matching speeds or duplex automatically putting another switch inbetween could help.

Auto will negotiate to the highest rate that both devices can handle, so either 10Mbit, 100Mbit, 1Gbit, 10Gbit etc.

 

[WildMonkey365]

If i am understanding correctly both are set to auto currently, and they are both negotiating 100Mbit full duplex? If so you don't need any additional hardware. If they are not matching speeds or duplex automatically putting another switch inbetween could help.

Auto will negotiate to the highest rate that both devices can handle, so either 10Mbit, 100Mbit, 1Gbit, 10Gbit etc.

Both the Port on the Router and the Port on the Switch are set to Auto Negotiation. I'm not getting any compliants the last few days but when I did (because of a delay in call Routing at the pop) I was in formed that the router which is gigabit, wasn't auto negotiating at 1000Mb full but at 100Mb full. The switch port connected to the router is also auto negotiating at 100Mb full. It's not a problem that a gigabit port is auto negotiating at 100Mb full unless the other side is not the same right? In other words gigabit devices can connect to 100Mb devices and as long as they are both auto negotiating at 100Mb full than it should be fine right?

 

[bill001g]

That is the whole purpose of the auto negotiation. The only time it causes trouble is when they do not match. It should always pick the fastest speed both device can run at.

Pretty much if the speed does not match the port will not even come up. The most common problem is if one get set to half duplex. If both would run half duplex it would sort work just slow. When one is full duplex and the other half what that means is the full duplex side assumes no data collisions can occur and does not even attempt to avoid transmitting at the same time. You tend to get massive packet damage. Then again nobody has used half duplex for many many years so I don't even really know why it is still supported.

 

[WildMonkey365]

That is the whole purpose of the auto negotiation. The only time it causes trouble is when they do not match. It should always pick the fastest speed both device can run at.

Pretty much if the speed does not match the port will not even come up. The most common problem is if one get set to half duplex. If both would run half duplex it would sort work just slow. When one is full duplex and the other half what that means is the full duplex side assumes no data collisions can occur and does not even attempt to avoid transmitting at the same time. You tend to get massive packet damage. Then again nobody has used half duplex for many many years so I don't even really know why it is still supported.

I install and maintain VoIP so what ever data transmission issues affect a network it will definitely even more so affect call quality. Thanks for all the info everyone!