3a. vnet0 and eth0 are in the same VLAN, so vnet0 can access the outside
world. vnet0 and ovsbr0 are in different VLANs, so vnet0 cannot
access the host IP.
3b. ovsbr0 and eth0 are in different VLANs, so ovsbr0 cannot access the
external world.
On Fri, Oct 04, 2013 at 10:40:58AM +0530, ashish yadav wrote:
> I have gone through OVS FAQ , but not able to understand Scenario 3 from
> FAQ.
> So could you please help me in same ?
>
>
> Thanks & Regards
> Ashish
>
>
> On Fri, Oct 4, 2013 at 10:16 AM, Ben Pfaff <b...@nicira.com> wrote:
>
> > The results you explain in all of your scenarios are what I would expect
> > to happen. Did you read the introduction to VLANs in the OVS FAQ?
> >
> > Q: What's a VLAN?
> >
> > A: At the simplest level, a VLAN (short for "virtual LAN") is a way to
> > partition a single switch into multiple switches. Suppose, for
> > example, that you have two groups of machines, group A and group B.
> > You want the machines in group A to be able to talk to each other,
> > and you want the machine in group B to be able to talk to each
> > other, but you don't want the machines in group A to be able to
> > talk to the machines in group B. You can do this with two
> > switches, by plugging the machines in group A into one switch and
> > the machines in group B into the other switch.
> >
> > If you only have one switch, then you can use VLANs to do the same
> > thing, by configuring the ports for machines in group A as VLAN
> > "access ports" for one VLAN and the ports for group B as "access
> > ports" for a different VLAN. The switch will only forward packets
> > between ports that are assigned to the same VLAN, so this
> > effectively subdivides your single switch into two independent
> > switches, one for each group of machines.
> >
> > So far we haven't said anything about VLAN headers. With access
> > ports, like we've described so far, no VLAN header is present in
> > the Ethernet frame. This means that the machines (or switches)
> > connected to access ports need not be aware that VLANs are
> > involved, just like in the case where we use two different physical
> > switches.
> >
> > Now suppose that you have a whole bunch of switches in your
> > network, instead of just one, and that some machines in group A are
> > connected directly to both switches 1 and 2. To allow these
> > machines to talk to each other, you could add an access port for
> > group A's VLAN to switch 1 and another to switch 2, and then
> > connect an Ethernet cable between those ports. That works fine,
> > but it doesn't scale well as the number of switches and the number
> > of VLANs increases, because you use up a lot of valuable switch
> > ports just connecting together your VLANs.
> >
> > This is where VLAN headers come in. Instead of using one cable and
> > two ports per VLAN to connect a pair of switches, we configure a
> > port on each switch as a VLAN "trunk port". Packets sent and
> > received on a trunk port carry a VLAN header that says what VLAN
> > the packet belongs to, so that only two ports total are required to
> > connect the switches, regardless of the number of VLANs in use.
> > Normally, only switches (either physical or virtual) are connected
> > to a trunk port, not individual hosts, because individual hosts
> > don't expect to see a VLAN header in the traffic that they receive.
> >
> > None of the above discussion says anything about particular VLAN
> > numbers. This is because VLAN numbers are completely arbitrary.
> > One must only ensure that a given VLAN is numbered consistently
> > throughout a network and that different VLANs are given different
> > numbers. (That said, VLAN 0 is usually synonymous with a packet
> > that has no VLAN header, and VLAN 4095 is reserved.)
> >
> > On Fri, Oct 04, 2013 at 10:12:08AM +0530, ashish yadav wrote:
> > > Hi,
> > >
> > > Could anyone please look into these fundamental queries of OVS & Vlan
> > and
> > > reply ?
> > >
> > >
> > > Thanks & Regards
> > > Ashish
> > >
> > >
> > > On Thu, Oct 3, 2013 at 9:42 PM, ashish yadav <ashishyada...@gmail.com
> > >wrote:
> > >
> > > > Hi,
> > > >
> > > > I was doing some exercise, came across few scenario.
> > > > I need help to understand these cases.
> > > >
> > > > *Environment: *
> > > > a. One Host and one VM in it
> > > > b. OVS running:
> > > > [root@sholay ashish]# ovs-vsctl show
> > > > 2b113c03-81e5-4c90-ba6c-b2eb2381432a
> > > > Bridge "ovsbr0"
> > > > Port "ovsbr0"
> > > > Interface "ovsbr0"
> > > > type: internal
> > > > Port "vnet0"
> > > > Interface "vnet0"
> > > > Port "eth0"
> > > > Interface "eth0"
> > > > ovs_version: "1.4.6"
> > > >
> > > > VM is up and I am able to ping:
> > > > a. External World from VM & Host.
> > > > b. Ping between HOST & VM fine.
> > > >
> > > > *Scenario 1:*
> > > > vnet0 is vlan tag:
> > > > [root@sholay ashish]# ovs-vsctl show
> > > > 2b113c03-81e5-4c90-ba6c-b2eb2381432a
> > > > Bridge "ovsbr0"
> > > > Port "ovsbr0"
> > > > tag: 0
> > > > Interface "ovsbr0"
> > > > type: internal
> > > > Port "vnet0"
> > > > tag: 5
> > > > Interface "vnet0"
> > > > Port "eth0"
> > > > tag: 0
> > > > Interface "eth0"
> > > > ovs_version: "1.4.6"
> > > >
> > > > a. From VM, not able to ping Host machine & External world.
> > > > b. From Host, able to ping External world.
> > > >
> > > > This is desired behaviour. No problem here.
> > > >
> > > >
> > > > *Scenario 2:*
> > > > ovsbr0 & vent0 are Vlan Tag:
> > > > [root@sholay ashish]# ovs-vsctl show
> > > > 2b113c03-81e5-4c90-ba6c-b2eb2381432a
> > > > Bridge "ovsbr0"
> > > > Port "ovsbr0"
> > > > tag: 5
> > > > Interface "ovsbr0"
> > > > type: internal
> > > > Port "vnet0"
> > > > tag: 5
> > > > Interface "vnet0"
> > > > Port "eth0"
> > > > tag: 0
> > > > Interface "eth0"
> > > > ovs_version: "1.4.6"
> > > >
> > > > a. VM is able to Ping host, but Fail to ping External world.
> > > > * Why it is so ?*
> > > > b. Host Machine Fail to ping External world.
> > > > *Why its is so ?*
> > > >
> > > >
> > > > *Scenario 3:*
> > > > eth0 & vent0 are Vlan Tag:
> > > > [root@sholay ashish]# ovs-vsctl show
> > > > 2b113c03-81e5-4c90-ba6c-b2eb2381432a
> > > > Bridge "ovsbr0"
> > > > Port "ovsbr0"
> > > > tag: 0
> > > > Interface "ovsbr0"
> > > > type: internal
> > > > Port "vnet0"
> > > > tag: 5
> > > > Interface "vnet0"
> > > > Port "eth0"
> > > > tag: 5
> > > > Interface "eth0"
> > > > ovs_version: "1.4.6"
> > > >
> > > > a. VM able to ping external world, but fail to ping host ip.
> > > > * Why it is so ?*
> > > > b. Host Machine not able to ping external world.
> > > > *Why VM can excess external world, but host not ?*
> > > >
> > > >
> > > > Thanks & Regards
> > > > Ashish
> > > >
> > > >
> >
> > > _______________________________________________
> > > discuss mailing list
> > > discuss@openvswitch.org
> > > http://openvswitch.org/mailman/listinfo/discuss
> >
> >
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