VMAN

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Hi,

please help how to configure a VMAN. thanks
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Marlon

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Posted 4 years ago

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Paul Russo, Alum

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Hello Marion.  a VMAN is really the same as a VLAN. It is created using the create vman command and you configure the tag and add ports the same way as a VLAN.

For example
create vman extr
config extr tag 100
config extr add port 1 tag

 Summit-PC.5 # sh vman
---------------------------------------------------------------------------------------
Name            VID  Protocol Addr        Flags                Proto  Ports  Virtual
                                                                      Active router
                                                                      /Total
---------------------------------------------------------------------------------------
extr            100  -------------------- ----------------------------- ANY    1 /1   VR-Default
---------------------------------------------------------------------------------------
Flags : (a) Learning Domain, (B) 802.1ah Backbone VMAN,
        (c) 802.1ad customer VLAN, (C) EAPS Control vlan, (E) ESRP Enabled,
        (f) IP Forwarding Enabled, (F) Learning Disabled, (i) ISIS Enabled,
        (I) IP Forwarding lpm-routing Enabled, (L) Loopback Enabled,
        (m) IPmc Forwarding Enabled, (n) IP Multinetting Enabled, (N) Network LogIn vlan,
        (N) Network LogIn vlan, (o) OSPF Enabled, (O) Flooding Disabled,
        (p) PIM Enabled, (P) EAPS protected vlan, (r) RIP Enabled,
        (S) 802.1ah Service VMAN, (T) Member of STP Domain, (v) VRRP Enabled,
        (V) VPLS Enabled, (W) VPWS Enabled

Total number of vman(s) : 1
* Summit-PC.6

using the command show vman ethertype will show the ethertype used for the tag.  In XOS it defaults to the standard 0x88a8.  to change the ethertype use the command config vman etherype

Does that help?

P
(Edited)
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Marlon

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Hi Paul,

thanks for the info. how can we add a vlan (Tagged or Untagged) to a vman? the tagged port of a vman is connected to another switch with vman? is this correct? sorry for my english. thanks
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Paul Russo, Alum

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Hello Marion

In order to put a VLAN into a VMAN you need to have two switches so for example we cant bring in traffic into a VLAN on port 1 of a switch and go out port 10 in a VMAN.

So in order for us to do this you will have the VLAN switch, like at the edge of a customer prem where that traffic is tagged on the uplink.  That uplink port, from the VLAN edge switch gets connected into an untagged port on the switch running the VMAN.  What happens is that since the traffic coming into the VMAN will have a tag of 8100 the VMAn will see it as untagged traffic as the VMAN is set to recognize 88a8 traffic.  That edge VMAN switch then gets connected to the other VMAN switches over a tagged link. see below

VLAN SW T-------(U)VMAN(T)------(T)VMAN(U)-----(T)VLAN


Does that help?

P
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Marlon

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Hi Paul,

thanks a lot. very nice and simple explanation. this helps a lot.

Regards,
Marlon
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Paul Russo, Alum

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great let us know if you run into any issues during your testing or if there are any new questions

P
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Marlon

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Noted. thanks
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Marlon

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Hi Paul,

we alredy test the vman and it works. :)

VLAN SW T-------(U)VMAN(T)------(T)VMAN(U)-----(T)VLAN

when we try to Tag the ports of vman facing vlan SW, we cannot ping. will this setup be possible?

VLAN SW T-------(T)VMAN(T)------(T)VMAN(T)-----(T)VLAN
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Paul Russo, Alum

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Hello Marion

In your second design where you have the VMAN ports tagged to the VLAN SW that will not work because the ethertype is a different number.  The VLAN ethertype is 8100 so the switches at the edge are looking for that header to read the VLAN ID number.  The VMAN is using ethertype 88a8.

When the VMAN port to the VLAN switch is untagged then the VMAN accepts all of the VLAN traffic because in its view it is an untagged packet.  i.e. 8100 doesn't mean anything to him.  The VMAN switch then adds it's tag to the packet to create the tunnel across the VMAN network and the other side strips it to the VLAN switch.  This is really no different then how VLANs work we are just telling the switch to use a different ethertype for the VMAN.


Does that help?  Does it make sense?

P
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Marlon

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Hi Paul,

the design is not possible? what if we change the ethertype of vman to 8100?
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Paul Russo, Alum

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Hey Marion


If you are going to do that then just tag the VLAN across as it wont really provide any different aspect.

Thanks
P
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Paul Russo, Alum

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To be clear you can do 8100 on the VMAN but you would have to map the VLANs from the edge to the VLANs in the core which may be a major management headache.  If you don't properly match it then you can get inter VLAN leaking because a VLAN can have the same tag as a VMAN .  This is why the standard is to use a different ethertype.

P
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Marlon

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hi Paul,

Got it. thanks for your time.