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Docop
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CRS305-1g-4s 10g proper description and Mtu transparent?

Tue Sep 06, 2022 2:41 am

Hi

So while i did get the nice unit CRS305-1g-4s like 3yrs ago, i finally plug it in, but description being so bad.. that was the reason i did not used it before.

Basically this is a super nice 10g HUB. You plug dc power and 1 dac cable to your router and hop you have full 10g network on other port. Why the description is not easily written : 10g hub with 1 eth port downspeed at 1g ! ? They only put everywhere it's a management port, that is quite useless, but no: the eth port is a full feature and working connection to be usable on the same network.
If people want to try the limited option of the crs305.. then yes play with the management and check the onboard swos.. But mostly the key selling point is being a great hub at great price.

On that side, is the unit is fully transparent for Mtu or any setting need to be put inside as mtu9000 to set proper speed ? usually it's quite only the end device that get the setting and hub is transparent.. Just to confirm that.

Thanks in advance for precision
 
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mkx
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Re: CRS305-1g-4s 10g proper description and Mtu transparent?

Tue Sep 06, 2022 3:18 pm

The device is not a hub, it's a switch (if you don't know the difference, google it up). Since the 1Gbps port is also handled by switch chip I don't see why it would be wrong to include it (by default) to common switch group. MT devices are all extremely versatile and it's easy for admin to change it according to their needs (e.g. removing RJ45 port from switch group and use it as management port only).

As to MTU: there are two uses of it:
  1. property of IP interface. When device needs to send out data, originating from its own IP stack, it consults the set value and fragments datagram to chunks (segments) of appropriate size.
  2. property of hardware port
    this is largely reflecting limit of hardware to receive large frames. Most of time it has no sense to set it lower than hardware capability as it will only have effect to drop frame which has excessive size. If all devices in given network behave properly (i.e. properly fragment datagrams to MTU-sized chunks as described in bullet #1 above), then this will not ever happen so no use to fuss about it.
    In ROS this is actually referred to as l2mtu property.

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