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Jumbo Frames on 2848 Switches

Errol Neal
Occasional Visitor

Jumbo Frames on 2848 Switches

So we bought the 2848 switches long before Jumbos had been implemented. So we recently upgraded the the firmware of our 2848's across our infrastructure to take advantage of them - not realizing that the feature implemented kind of awkwardly, at least from our perspective. HP choose to have Jumbo Frame configuration on a per-vlan basis. Which doesn't make a-lot of sense to me since it's a deviation from all other configuration parameters like port speed, duplex and etc. But anyways. In the segment that I'd like to take advantage of JF's, the network is just flat. We do not use vlans there. What is the way that HP recommends that I implement JFs? Do I need to create a vlan specifically to support this or can I apply the appropriate configuration directives to vlan 1? If the later is true, I've already tried that with no success. Any advice will be much appreciated.

Thanks,

Errol Neal
2 REPLIES
Mohieddin Kharnoub
Honored Contributor

Re: Jumbo Frames on 2848 Switches

Hi

Switch#config
Switch(config)#vlan 1 jumbo

Good Luck !!!
Science for Everyone
rick jones
Honored Contributor

Re: Jumbo Frames on 2848 Switches

Strictly speaking, _all_ stations in the same broadcast domain must have the same MTU. In that sense, making jumbo frame a property of the VLAN does make some sense.

Mixing MTUs in the same broadcast domain is basically a problem waiting to happen.

Now, you could indeed apply the jumbo frame property to the default vlan (as previously suggested), It won't in and of itself do anything bad to systems retaining a 1500 byte MTU. Just keep in mind that as you selectively enable jumbo frame on your end stations, you could have problems with mixed MTUs - one station at 1500, another at 9000. That TCP connections still "work" in such situations is really just an accident. UDP traffic _will_ have problems in a mixed MTU situation.
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