Date: Wed, 12 Mar 2008 15:34:00 -0700 From: Sean Chittenden <sean@chittenden.org> To: Andrew Thompson <thompsa@FreeBSD.org> Cc: freebsd-net@FreeBSD.org, Giulio Ferro <auryn@zirakzigil.org> Subject: Re: VLAN trunking and fragmentation Message-ID: <F2EE5F57-729D-49CC-BD01-A246008F7A68@chittenden.org> In-Reply-To: <20080312221314.GA4458@heff.fud.org.nz> References: <47D7C34E.8060805@zirakzigil.org> <D8BE14C3-9897-4F19-A5AC-6770995423E5@chittenden.org> <20080312221314.GA4458@heff.fud.org.nz>
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>>>> interface ethernet 1/g1 >>>> switchport mode trunk >>>> switchport trunk allowed vlan add 10 >>>> exit >>> I think this is an issue with default VLAN membership. >> >> I don't think it's where the problem lies, otherwise even a simple >> ping >> wouldn't work. The problem here explicitly arises when packets are >> fragmented... > > fragmentation? > I think, you use ethernet links, all have 1500byte max packet size, > you have 1500byte packet size also comfigured at the vlan interface, > so.. > why do you think anything should start fragmenting? > (and tagged vlan frames are bigger than 1500byte at the "raw" > ethernet link). > > check for maximum mtu that can travel over the link. > (ping -s 1472 for 1500byte packet) It's the MTU size, not the fragmentation or VLAN membership. The use of a default VLAN can cause problems potentially because the size of each frame can vary and, IMHO, is the cause of the problem. By default VLAN membership, I don't mean to suggest you've got your port tagged in the wrong VLAN. Switch all traffic to 802.1q tagged and you should see everything work. Use of VLANs reduces the MTU size automatically, but cycling between the two? Likely a no-go and the source of your problems. > Even nicer is using <interface>.<number> autoconfig, the following is > equivalent to above: > > cloned_interfaces="re0.10 re0.11" > ifconfig_re0="media 100baseTX mediaopt full-duplex" > ifconfig_re0.10="inet 192.168.60.1 netmask 255.255.255.0" > ifconfig_re0.11="inet 192.168.100.1 netmask 255.255.255.0" *boggles* That's hawt! 'ya learn something new every day, thanks! :~] -sc -- Sean Chittenden sean@chittenden.org http://sean.chittenden.org/
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