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VLAN Setup

VLAN Setup
Occasional Visitor

VLAN Setup

Have HP ProCurve 2524 and trying to set a vlan for ip based pbx usage. There are three buildings on this site and not sure how to set up the vlan. The following setup follows:

switch A is Bldg 1 that houses the pbx
switch B is Bldg 2 housing switches only
switch C is Bldg 3 housing phones needed to connect to pbx

Created a vlan in all three switch stacks (A, B, C) but am unable to ping from C to A or B. Ports are all untagged.

This is probably easy for someone who lives and breathes this stuff but I do not. Any help greatly appreciated.
Mohieddin Kharnoub
Honored Contributor

Re: VLAN Setup


Usually, the Switch comes with 1 Default-Vlan with ID=1, and if yo uwant more, you can create on the switch but in this case you need to do routing between these Vlans so they will be able to communicate between each other.

The switch you have 2500 series doesn't have routing between the connected Vlans, so if your plan to have more than one Vlan crossing all the Switches and routed to other Vlans, they you need an External Router to do that.

Basically what you can do is:
Just keep the default vlan as it is, and connect cables between the switches, in this case all the switches have one vlan (the Default) shared between them, and keep the ports also untagged since you don't have more than one Vlan.

You don't have to have different IP Subnet on each switch since they all part of the same Vlan = Same Subnet, say you dedicate for first building, for second, for the third.

If that was not enough to explain, then i prefer you attach the config of your switches here so we can sort it out together.

Good Luck !!!
Science for Everyone
VLAN Setup
Occasional Visitor

Re: VLAN Setup

I was wanting to do this on my existing switches as I have them configured with 2 vlans. The default and one for the pbx. Is it possible to set this up without using an external router? I would think that since they are connected by fiber I should be able to route normally without an external router.

Configuration is setup as follows:

Default vlan Bldg A - 10.1.1.xxx
PBX vlan Bldg A -

Default vlan Bldg B - 10.1.1.xxx
PBX vlan Bldg B -

Default vlan Bldg C - 10.1.1.xxx
PBX vlan Bldg C -

The data network is running on 10.1.1.xxx while I have sectioned off part of the ports on the switch for the pbx connection. I would think that I would not need a router to make this work. I'm I right?
Trusted Contributor

Re: VLAN Setup

If you do not need hosts in one VLAN to exchange information with hosts in the other VLAN, then you will not need a router to perform the routing between the subnets associated to each VLAN.

If you need hosts in one VLAN to be able to communicate to hosts in the same VLAN, but which are connected in different switches, then you need to set the ports that connect the switches (the uplink ports) so that they carry both VLANs over the uplinks (the DEFAULT_VLAN may be left untagged, but the PBX_VLAN must be tagged).

Across all 3 switches, DEFAULT_VLAN must be defined with the same 802.1Q ID (which is always 1) and the PBX_VLAN must be defined, also, with the same 802.1Q ID (for example 2).

802.1Q IDs are the tags that switches put in front of each ethernet frame, so the receiving switch knows on which port to forward the frame (or on which ports, if the frame is a broadcast frame having the destination MAC address FF:FF:FF:FF:FF:FF).

Before the switch forwards a frame to a computer/printer or to a switch/hub without management, it strips the VLAN information from the first part of the frame, since the vast majority of the operating systems do not know what to do with a tagged frame (and they do not expect tagged frames): this is why the ports of the switch where computers/printers or flat switches/hubs are attached must be defined as untagged.

If you assign IP addresses to VLAN interfaces on the switch, anybody in that subnet can stumble on your switches and try to hack them or perform denial of service on them: I do not assign IPs to switch VLAN interfaces for the subnets my users live in. Instead I use DEFAULT_VLAN for the purposes of switch administration, and create more VLANs for users.