From: Jeff Mullan (jmullan78@gmail.com)
Date: Fri Feb 23 2007 - 02:54:31 ART
Thanks folks. May be I wasnt clear in the begining but my question is
specific to a "Router on a Stick" Scenario. Would it make sense to have the
allow VLAN command on the switch which is talking to the router.
Thanks,
JM
On 2/22/07, Dwi C Taniel <dc@dwichandra.info> wrote:
>
> Hi Lou and Jeff,
>
> I agree with Lou, to force certain vlan to be allowed through certain
> trunk must be well justified as you are forcing those vlans to
> traveverse through certain trunk ports only (and maybe not another).
> Thus if that particular trunk that only provides path access to
> certain switch, you are going to break the VLAN member nodes into
> several isolated network until the trunk carrying those VLANs can go
> back up.
>
> In using VTP client, yes, 64 VLANs is the 'jinx' that cought me up
> thinking the VTP is not working in client-server mode.
> It happen in the past when I was first introduced to VTP using Cat4k
> and Cat6.5k (fresh from the oven at that time ;) )
>
> Besides, if using VTP pruning would do the job, then why bother
> manually fine tuning the VTP settings?
> The trade off between those two are:
> - With manual VTP fine tuning, you really controlling the actual VLANs
> flowing through certain VTP link. This will also reduce the switch CPU
> utilization as it just 'forced' to pass through certain trunk for
> certain VLANs
> - With VTP pruning, you will have less administrative overhad (tasks)
> since you are giving it to the switch (and it's miraculous VTP/STP
> algorithm to put into work). But, using this method, your switch CPU
> tend to work more than the previous option.
>
> If switch CPU is not much of a concern, then VTP pruning would be
> better options.
>
> Happy Friday everyone! :)
>
> DC
>
> On 02/23/2007, Lou Ioanni <louisccie_r_s@yahoo.com> wrote:
>
> > I would say is good to use the allow statement if you know what you
> > doing. If you using VTP server/client many switches can support 64
> > vlans and if you do not use the allow statements and allow all vlans
> > to go through you might experience network downtime.
> >
> > I had an experience where they were using the allow statement and
> > someone just removed it and the whole network slowed down because
> > switches could not support all vlans that went through. Especially
> > they created another 200 vlans for NAC clean access that day too.
> >
> > Many get around this by using Transparent mode instead of
> > server/client VTP mode.....especially if you have cores at L3 and no
> > distribution L3 you should be carefull with using server/client
> > mode...especially without allow statements.
> >
> > Thanks,
> >
> > Loizos Y.
> > CCIE#10702 R & S
> >
> > Jeff Mullan <jmullan78@gmail.com> wrote:
> > Folks,
> > For example, if between a switch and router there are only 2 Vlans
> active (
> > say vlan 10,11) vlan 10 being native and switch is a trunk port , do
> need to
> > have the "switch port mode allowed vlan 10,11" command ? Ideally if we
> dont
> > have it configured then the router will drop all vlans without tags
> 10,11
> > but just wanted to find out from a best practice point of view ? Thanks
> !!
> >
> >
> > interface FastEthernet0/6
> > switchport trunk encapsulation dot1q
> > switchport trunk native vlan 10
> > switchport trunk allowed vlan 10,11 <=================
> > switchport mode trunk
> > end
> >
> > SW_1#
> >
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