On 29/05/12 15:41, CiscoNSP_list CiscoNSP_list wrote: > > Are there any "issues" with setting mtu at 9000? (We have a mix of > routers/switches some of which only support mtu of 1500), so is adding a new > switch(or adjusting an existing switch(3560+2960)) going to cause issues if > other connecting devices mtu is smaller?
With switches doing L2 only it's worth making a difference between L3 interface MTU and L2 transit MTU. There's a bunch of switches where the two can be different (I remember one switch, can't remember from who, doesn't allow L3 above 1500, but L2 can be 9k). There's a few things to remember: - All L3 devices on a jumbo VLAN must share the same MTU - Any L2 devices can use a larger MTU - This may not be the same number in the configuration (eg, IOS vs IOS XR/JunOS) - Many devices can't fragment in the fast path, so make sure path MTU discovery is working You also should standardise what jumbo means in your enviroment, and standardise on two/three values (1500, jumbo, and jumbo+QinQ/MPLS). This makes it much easier to audit and document. -- Julien Goodwin Studio442 "Blue Sky Solutioneering"
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