[c-nsp] Adjusting MTU on 802.1q links

[Matthew Huff]

I have. A cisco 3750, but an older release. Must be a bug. But wanted to know if it was a general problem overall. Doesn't look like it.


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> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Phil
> Mayers
> Sent: Friday, December 03, 2010 10:58 AM
> To: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Adjusting MTU on 802.1q links
> 
> On 03/12/10 13:49, Matthew Huff wrote:
> > I don't know why it never occurred to me, but on 802.1q trunk links,
> > non-native vlans are encapsulated within 802.1q headers, therefore
> > max packets would have to be fragmented. On trunks that support it,
> > should standard practice to bump up the mtu on both sides to account
> > for the 802.1q header.
> 
> No. 802.1q trunks do this automatically i.e. bump MTU from 1518 to 1522
> to account for the extra space. I've never seen a switch platform that
> needed any special config for this to work.
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