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Vlan Id

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Sumanth N
Occasional Advisor

Vlan Id

is it Possible to configure vlans with same ID in 2 sperate braodcast domains. If Possible how can it be done, and how packets are seperated ??
I it based on VlanId or something else TagId??
5 REPLIES
Igoris_1
Frequent Advisor

Re: Vlan Id

If they are separated sure you can. It is the same if VLAN ID 1 is in company A and VLAN ID2 is in company B. Just make sure they are indeed separated.
VLAN ID actually is the tag number.
Why do you need the same VLAN ID?
Sergej Gurenko
Trusted Contributor

Re: Vlan Id

Technically: You can use same VLAN ID for the different purposes and reuse VLAN ID's on the different switches if you do not forward them (q-trunk) between switches.
Logically: This is not a good idea. This will a common misconfiguration/misunderstanding problem.
Kell van Daal
Respected Contributor

Re: Vlan Id

As the previous two posters noted, it is indeed possible, but it can create a complex, non-transparant network design.
If the two VLAN's need to communicate with eachother, just make sure that traffic between them is routed and not bridged.

If you care to state why you want to use the same VLAN ID twice, we may be able to supply you with an (better) alternative.
NicholasH
Occasional Visitor
Solution

Re: Vlan Id

Absolutely.
In fact, this is the setup I work with.
Two sites, each has VLAN 1,2,3, & 8
VLAN 1 is for servers and network appliances.
VLAN 2 is for workstations.
VLAN 3 carries IP Telephony.
VLAN 8 acts as routing network between the two sites.
We could have simply extended the VLANs across the WAN link by passing tags, but using the aforementioned configuration keeps a lot of unnecessary traffic off our WAN link.
By using VLAN 8 strictly for routing, the delivery decision between VLANs in different sites is based on simple Layer-3 routing principles.

At the smaller site, we have two ProCurve 2650's that are joined in a 2Gb trunk.
Only traffic for VLANs 2 & 3 are allowed on the trunk, as all of our servers are located in the same area and (presently) are connected to the same switch. Whereas our workstations and phones are spread out over two floors. VLANs 2 & 3 are both tagged on the trunk, but only 3 is tagged on the "regular" ports workstations get connected to.
Sumanth N
Occasional Advisor

Re: Vlan Id

Thanks for all the replies.
It really helped me.