JUMBO FRAMES

[carl_townshend]

I just spoke to a colleugue and he said are we using jumbo frames there for your backups, can anyone enlighten me on this issue

thanks

Carl

[arvindchari]

I think jumbo frames refers to giant frames.

Here is what I came up with on them

http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration_example09186a008010edab.shtml

[carl_townshend]

does this make much difference to the speed of my backups ?

[spremkumar]

Hi Carl

Can you be more specific on what kinda backups you are talking about here ??

regds

[carl_townshend]

basically out server backups, mail, file servers etc across my lan !!

[Marvin Rhoads]

Jumbo frames can definitely make a difference in throughput and server load. Here is one citation supporting this assertion: http://www.small-tree.com/jumbo5.htm

Jumbo frames need to be enabled on both your host and any intervening network equipment.

Hope this helps. Please rate helpful posts.

[carl_townshend]

would I change the mtu for the whole switch or particular interface ?

[Marvin Rhoads]

For some switches (e.g., Catalyst 6000 series), jumbo frame support is configured at the port level. Others have it as a global setting. Some don't support jumbo frames at all. See the configuration guide posted above by arvindchari for details and syntax.

[carl_townshend]

Can anyone suggest a good size to set my mtu as, this wont cause any problems with my normal traffic I presume ? what does everyone else set theres as ?

I think its between 1500 and 9000 ?

thanks

[Anand Narayana]

Changing the MTU size on 6500 series switches will be applicable for port level, where as for switches like 3550,3750 it will apply for all the ports by default.in this case you need to restart the switches.

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[carl_townshend]

will this cause any problems with any other equipment plugged into the switch

[Anand Narayana]

ofcourse YES, if the JUMBO frames is set for 9000 in 3750 & the PC's have the frame size less than 9000 or any un-manageable Switch(1500) which can't be changed, also Frame size can be changed in 10/100/1000 Mbps NIC cards i am not sure the newer 10/100 Mbps NIC will support max. of 9000.

Plz. rate the post.

[carl_townshend]

so will it cause me any problems, I have 2 servers and lots of pcs plugged into 1 switch, I want the traffic between the servers use jumbo frames, Its a 3550 switch, will this cause any issues with the other machines in the switch

[Anand Narayana]

if JUMBO frames are enabled in 3550, it wil get enabled in all the ports, so what ever machines are connected directly in 3550 whose NIC doesn't support 9000, will definetly affects the performance.

[bhedlund]

I dont see how this would cause problems. If a port is configured for an MTU of 9000 and its link partner is sending in frames no larger than 1500 the switch will still forward the traffic as normal as there is no MTU violation.