Introduction
As you lot would move aware a switched network creates i broadcast domain, like to that of a VLAN powered network where all nodes belonging to the same VLAN are purpose of the same broadcast domain, receiving all broadcasts sent on their network.
The Broadcast And Unicast Problem In VLAN Networks
What nosotros are nearly to encounter is how these broadcasts tin give the axe genuinely create problems yesteryear flooding the VLAN network amongst unnecessary traffic, in addition to depending on your network setup, this tin give the axe seek to move a huge problem. The argue for this is because the body links interconecting your network switches volition bear these broadcasts to every switch inwards the network, regardless of which VLAN the broadcast is intended for.
As shown in addition to described, a host connected to a port configured for VLAN 2 on Switch 1 (first switch on the left), generates a network broadcast. Naturally, the switch volition frontward the broadcast out all ports assigned to the same VLAN it was received from, that is, VLAN 2.
In addition, the Catalyst switch volition frontward the broadcast out its body link, so it may attain all ports inwards the network assigned to VLAN 2. The Root switch receives the broadcast through i of it's trunks in addition to instantly forwards it out the other 2 - towards Switch 2 & 3.
Switch 2 is delighted to have the broadcast equally it does inwards fact have got i port assigned to VLAN 2. Switch three however, is a unlike instance - it has no ports assigned to VLAN 2 in addition to thence volition drib the broadcast bundle it receives.
In this example, the bandwidth usage was ineffecient because i broadcast bundle was sent over all possible body links, in addition to was in addition to so dropped yesteryear Switch 3.
You mightiness inquire yourself 'So what's the big deal?'.
The work hither is pocket-size in addition to tin give the axe easily move ignored... but catch a network of 15 or to a greater extent than 12 port switches (this translates to at to the lowest degree 210 nodes) in addition to you lot tin give the axe start to appreciate how serious the work tin give the axe get. To brand things worse (and to a greater extent than realistic), catch you're using 24 port switches, in addition to so you're all suddenly talking nearly to a greater extent than than 300 nodes!
To farther attention empathise how serious the work gets, let's accept a expect at our illustration network below:
Here nosotros have got a medium sized network powered yesteryear Cisco Catalyst switches. The 2 brain switches upward the gain are the VTP servers in addition to too perform tertiary layer switching yesteryear routing packets betwixt the VLANs we've created.
Right below them you'll discovery our 2950's Catalyst switches which are connected to the marrow switches via redundant fiber body links. Directly below our 2950's are our 2948 Catalyst switches that connect all workstations to the network.
Influenza A virus subtype H5N1 workstation connected to a port assigned to VLAN 2 decided to mail a network broadcast looking for a specific network resource. While the workstation is totally unaware of our network pattern in addition to complexity, its broadcast is the argue all our trunks volition overflowing amongst unwanted traffic, consuming valuable bandwidth!
Let's accept a expect at what happens:
We don't scream back describing the higher upward is genuinely required equally the diagram shows all the data nosotros quest in addition to we're confident you lot volition grip that nosotros dealing amongst a big problem:)
So how create nosotros create this mess ?
Keep reading on equally you're nearly to learn........
The Solution: Enabling VTP Pruning
VTP Pruning equally you lot mightiness have got already guessed solves the higher upward work yesteryear reducing the unnecessary flooded traffic described previously. This is done yesteryear forwarding broadcasts in addition to unknown unicast frames on a VLAN over body links alone if the receiving destination of the body has ports inwards that VLAN.
Support For VTP Pruning
The VTP Pruning service is supported yesteryear both VTP 1 in addition to VTP 2 versions of the VTP protocol. With VTP 1, VTP pruning is possible amongst the usage of additional VTP message types.
When a Cisco Catalyst switch has ports associated amongst a VLAN, it volition mail an promotion to its neighboring switches informing them nearly the ports it has active on that VLAN. This data is in addition to so stored yesteryear the neighbors in addition to used to create upward one's take away heed if flooded traffic from a VLAN should move forwarded to the switch via the body port or not.
| Note: VTP Pruning is disabled yesteryear default on all Cisco Catalyst switches in addition to tin give the axe move enabled yesteryear issuing the "set vtp pruning enable" command. If this ascendency is issued on the VTP Server(s) of your network, in addition to so pruning is enabled for the entire management domain. |
When you lot enable VTP Pruning on your network, all VLANs buy the farm eligible for pruning on all body links. This default listing of pruning eligibility tin give the axe thankfully move modified to suite your needs but you lot must commencement clear all VLANs from the listing using the "clear vtp prune-eligible vlan-range" ascendency in addition to and so laid the VLAN gain you lot wishing to add together inwards the prune eligible listing yesteryear issuing the next command: "set vtp prune-eligible vlan-range" where the 'vlan-range' is the actual inclusive gain of VLANs e.g '2-20'.
By default, VLANs 2–1000 are eligible for pruning. VLAN 1 has a especial important because it is commonly used equally a management VLAN in addition to is never eligible for pruning, spell VLANs 1001–1005 are too never eligible for pruning. If the VLANs are configured equally pruning-ineligible, the flooding continues equally illustrated inwards our examples.
Summary
VTP Pruning tin give the axe inwards fact move an administrator's best friend inwards whatever Cisco powered network, increasing available bandwidth yesteryear restricting flooded traffic to those body links that the traffic must usage to attain the destination devices.
At this point, nosotros have got too come upward to the destination of the commencement purpose of our VLAN presentation. As nosotros are silent working on the instant in addition to in conclusion purpose of the VLAN topic, nosotros promise these pages volition maintain you lot going until it is complete.
