Date: Sun, 11 Mar 2012 11:12:11 +0330 From: h bagade <bagadeh@gmail.com> To: Peter Jeremy <peterjeremy@acm.org> Cc: freebsd-net <freebsd-net@freebsd.org> Subject: Re: problem with vlan interfaces tagging/untagging in a simulated switch box Message-ID: <CAKWOZ6Ue6mr-mHgQV--gqeSFK6ndRDEybmbn3dCQ3_bpYzSKJQ@mail.gmail.com> In-Reply-To: <CAKWOZ6WrYrFso7nhxqi_5Nm0Z8_YWNJwt5FaAjVS3dEeBRjCOA@mail.gmail.com> References: <CAKWOZ6VH5Jv9kd-QuCM3oiukwTUajMAOvmGeg1uofNa4A3UXjA@mail.gmail.com> <20120305084359.GA56606@server.vk2pj.dyndns.org> <CAKWOZ6Vog_uxEn8ea4Jm=RS_R0PHZ0Y9jndsFdn8OfHC5gPCNg@mail.gmail.com> <20120305222811.GA64183@server.vk2pj.dyndns.org> <CAKWOZ6Uqwgw7ro=_Sn8ycUPtC2BAYiAuBKza4W8-WL-gNScKrg@mail.gmail.com> <20120306074655.GA71641@server.vk2pj.dyndns.org> <CAKWOZ6WrYrFso7nhxqi_5Nm0Z8_YWNJwt5FaAjVS3dEeBRjCOA@mail.gmail.com>
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Sorry my last post was sent out suddenly by pressing a key, I don't
yet know even which one! the compelete post is written down here.
let me explain my problem with this type of topology when I want to
simulate a switch like cisco
eth0 -+
|
eth1 -+ --- bridge1 --- vlan9 --+-- eth4 -----
outside of switch
| |
eth2 -+ --- bridge2 --- vlan8 --+ |
|
eth3 -+ ------------ bridge3 -----------+
In above example, eth0 and eth1 are vlan9 ports which means that
traffic coming from these ports are sent out eth4(trunk port) with
vlan9 tag. the same for eth2 which is vlan8 port. eth3 is the port
with vlan id equal to native vlan on eth4. the native vlans are those
vlans which would not tag across trunk port, so traffic comes from
eth3 pass the trunk port(eth4) untagged.
the scenario works fine without eth3! it means that when eth3 is
excluded from the topology, the other ports are tagged the proper vlan
tag when going through eth4. As eth3 is added the all traffic receives
on eth4 are passed to eth3 with out cheching vlan tags! this is due to
bridge between eth3 and eth4! but I don't know how to correct the
scenario that eth3 packets to be not tagged through eth4 without
disturbing the function of other parts!
I would be very glad if someone help me on this important problem I've
encountered.
On 3/11/12, h bagade <bagadeh@gmail.com> wrote:
> let me explain my problem with this type of topology when I want to
> simulate a switch like cisco
>
>
>
> eth1 -+ --- bridge1 --- vlan9 --+-- eth0 --- trunk0
> |
> eth2 -+ --- bridge2 --- vlan8 --+
>
> On 3/6/12, Peter Jeremy <peterjeremy@acm.org> wrote:
>> On 2012-Mar-06 09:15:57 +0330, h bagade <bagadeh@gmail.com> wrote:
>>>On 3/6/12, Peter Jeremy <peterjeremy@acm.org> wrote:
>>>> The following example diagram shows 3 distinct packet flows:
>>>> - packets tagged 5 in trunk1 and 6 in trunk0
>>>> - packets tagged 7 in trunk1 and 9 in trunk0
>>>> - packets tagged 8 in trunk0 and 10 in trunk2
>>>>
>>>> +-- vlan5 --- bridge1 --- vlan6 --+
>>>> | |
>>>> trunk1 --- eth1 -+- vlan7 --- bridge2 --- vlan9 --+-- eth0 --- trunk0
>>>> |
>>>> bridge3 --- vlan8 --+
>>>> |
>>>> trunk2 -- eth2 --- vlan10
>>>>
>>>I've described the function of Cisco switches in vlan
>>>tagging/untagging.
>>
>> Real switches typically have everything tagged internally, with the
>> native VLAN tags added/removed at the ingress/egress ports. This
>> simplifies the internal switch logic (at the expense of meaning that
>> tags have to be consistent across all trunks).
>>
>> FreeBSD works differently. Packets are _untagged_ internally and you
>> need a separate bridge(4) device for each broadcast domain (vlan).
>>
>>> In your topology, packets should be tagged when
>>>recieved on real interfaces to be send out to vlan interfaces.
>>
>> Packets are never tagged by real interfaces and always have tags
>> added/removed by vlan devices.
>>
>>> It
>>>would be fine when two trunks are communicating because on both side
>>>packets are tagged. But as I mentioned before, Cisco switches receive
>>>packets on an interface untagged and then sending packets tagged out
>>>of trunk port, based on which interface it receives,
>>
>> You can connect a physical interface (ethX) directly to a bridge device
>> to access untagged packets. Note that I'm not sure whether it is safe
>> to access the native VLAN in a trunk in this way.
>>
>> To continue the above example,
>> ifconfig bridge1 addm eth3
>> would result in packets arriving on eth3 leaving tagged as vlan 5 in
>> trunk1, vlan 6 in trunk0 and vice versa.
>>
>> --
>> Peter Jeremy
>>
>
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