[CentOS] VLAN issue

Less,

You are 100% right. Of course I brought up my eth0 - but, like you said,
with no IP. Meanwhile, I brought up eth0.48 with 192.168.48.100.

However, until I would bring up eth0 with an IP address (any in the
network) I would have no connection. Why? That's what I fail to understand.

Boris.

On Fri, Jan 23, 2015 at 6:45 PM, Les Mikesell <lesmikesell at gmail.com> wrote:

> On Fri, Jan 23, 2015 at 5:27 PM, Boris Epstein <borepstein at gmail.com>
> wrote:
> > Hello all,
> >
> > I have a machine running Centos 6.6 connected to a port on a Cisco
> Catalyst
> > 3750 series switch. That port is part of VLAN 48. I have VLAN 48 on the
> > CentOS machine too.
> >
> > The IP network on VLAN 48 is 192.168.48.0/255.255.255.0. The address on
> the
> > CentOS side is 192.168.48.101, the address on the Linux end ought to be
> > 192.168.48.100.
> >
> > When I only bring up eth0.48 VLAN device with the IP=192.168.48.100 I
> have
> > no connectivity. If I bring it up along with eth0 with another VLAN 48
> > address assigned to it (for instance, 192.168.48.99) I do have
> connectivity.
> >
> > Also, strangely enough, sometimes to get things going I have to
> disconnect
> > the Linux host from the switch - physically detach the wire and reconnect
> > it again.
> >
> > Be that as it may when I just bring up the VLAN by itself I have thus far
> > been unable to get anywhere.
> >
> > Has anybody seen a situation like this? Does anybody have an explaination
> > for it?
>
> I think you always have  to bring up the underlying eth device to
> activate a related eth.nn vlan.  The base device would not normally
> have an IPADDR, though, unless it is for an untagged vlan 0.
> Assuming the connected switch port is configured as a trunk, you
> shouldn't see vlan 48 addresses on the base (untagged) device.
>
> --
>    Les Mikesell
>      lesmikesell at gmail.com
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