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private vlan

Hi,

What is private vlan? Can someone give some scenario that when the implementation of private vlan come in place?

2 REPLIES
Hall of Fame Super Blue

Re: private vlan

kevinlim62 wrote:

Hi,

What is private vlan? Can someone give some scenario that when the implementation of private vlan come in place?

Normally within a vlan all devices can communicate with each other at L2. With private vlans you segregate up one L2 vlan so that some hosts within the vlan cannot talk to other hosts within the same vlans. There are 3 types of ports within a private vlan -

1) promiscuos ports which can talk to any other port within the L2 vlan. The L3 interface for the vlan would normally be a promiscuos port

2) community ports - these ports can communicate with any other community ports and the promiscuos port

3) islolated ports - these ports can only communicate with the promiscuous port.

When would you use them ? Well a common example would be if you had a L2 vlan and the corresponding L3 subnet. You want to separate some of the devices within the vlan but you don't want to use another vlan because that would require readdressing. So you can use private vlans instead.

Jon

Silver

Re: private vlan

Hello,

In addition to Jon's very clear post allow me to attach a picture I like to use and which sums up IOS configuration considerations about pvlans.

Cheers

Karim

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