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is it possible to enable jumbo frames in VLAN?

Fullmetal Chocobo

Fullmetal Chocobo

Moderator<br>Distributed Computing
Moderator
My new gigabit switch gets here on Wednesday (HP 1800-24g), and I was wondering a quick question. Can I enable jumbo frames within a VLAN only? I'm looking to put wired machines on a VLAN so that I can have faster backups to my WHS box, as well as faster transfers from that file server.

I've checked, and the wired NICs have jumbo frame capability. I'm not sure if this is worth bothering with though.
 
Frames are not in the VLAN, the VLAN is in the frames.

What makes a VLAN is a tag, a number in a field, within the frame. SO whether the frame happens to be a Jumbo frame, or a regular 64-1500 byte Ethernet frame doesn't matter.

To do jumbo frames, every component within the broadcast domain (broadcast domain ~= "between routers") has to do jumbos. Beyond that, the protocol you are using must be able to support "fragmentation" so that if the traffic crosses into a "non-jumbo" span, the frames can be broken apart to fit. If the frames can't fit, and if they can be split to fit, they're dropped.

The problem is the packet inside the frame: Most, if not all, encrypted packets do not support fragmentation.

SO, the switch you plug into must do jumbo frames, the router you pass the traffic to (at least the one interface) must also support jumbo frames. Past that, the protocols in use must support fragmentation.
 
Similar question, and I think I already know the answer, but I would like confirmation. Say I have several computers connected to a gigabit switch. Also connected to that switch is a 10/100 internet router that has the WAN connection to the internet. I assume that even though the machines connected to the gigabit support jumbo (as does the gig switch), that if the 10/100 router doesn't support jumbo, then I cannot reliably enable jumbo frames on that LAN. Correct?
 
Originally posted by: Fullmetal Chocobo
My new gigabit switch gets here on Wednesday (HP 1800-24g), and I was wondering a quick question. Can I enable jumbo frames within a VLAN only? I'm looking to put wired machines on a VLAN so that I can have faster backups to my WHS box, as well as faster transfers from that file server.

I've checked, and the wired NICs have jumbo frame capability. I'm not sure if this is worth bothering with though.
Click to expand...

I have the same switch. Its a great switch. I run jumbo frames on it and everything seems to work great and fast.
 
For the LAN (LAN host to LAN host) sure, no problem. A switch is a switch because it provides a discreet, full-duplex path between host pairs. Unless the router is the originator or recipient of the unicast traffic, it shouldn't see it at all.

Multicast, broadcast, and flood traffic is, of course, sent to all ports except the ingress port.

For anything going out to the Internet, it won't help, and it might hurt (depending on the type of traffic).
 
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