Ethernet Switching
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Posts: 5
Registered: ‎09-23-2009
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VLAN on a logical unit interface or physical interface

I'm actually attending a Juniper sponsored security class at the moment and our LAB books had us create two VLANs as physical interfaces for connecting to some virtual routing instance objects.  In my own work environment all of our VLANs are created as logical interfaces using RVIs.


Is there a district advantage to using one method or another?  Performance?  Reliability?


For a concrete example the LAB book suggests creating a physical VLAN interface like:

set ge-0/0/x vlan-tagging

set ge-0/0/x unit 100 vlan-id 100

set ge-0/0/x unit 100 family inet address 192.168.1.x/24


I learned to create VLAN interfaces logically like so:

set vlan vlan100 vlan-id 100 l3.interface vlan.100

set interface vlan unit 100 family inet address 192.168.1.x/24

set interface ge-0/0/x unit 0 family ethernet switching port-mode access vlan members vlan100



Posts: 35
Registered: ‎09-28-2009
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Re: VLAN on a logical unit interface or physical interface



The only difference I have come across is that as a physical interface no other ports on that switch can be in that vlan. But as a physical interface it is easy to get snmp stats whereas I have difficulty getting stats of an RVI


Hope this helps some

Distinguished Expert
Posts: 1,127
Registered: ‎01-10-2008

Re: VLAN on a logical unit interface or physical interface

The big difference is the mode your using for the port layer2 vs layer3. In layer 2 you can combine switching (putting multiple ports in the same vlan) with the secuirty features of a SRX/ J-series.

best regards,

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Distinguished Expert
Posts: 2,248
Registered: ‎08-21-2009

Re: VLAN on a logical unit interface or physical interface

[ Edited ]

Hello there,

First method works on any JUNOS platform I know of.

Second method works only on J-series and EX kit.

There is a third one with IRB interfaces on MX which are nearly equivalent to RVI.

If you are not doing L2 switching between interfaces I would always recommend  1st method because of:

1/ compatibility

2/ usability for redundant links design: how do plan for 2nd method if You must use 2 redundant L3 links with same VLAN tag and two different /30 subnets? AFAIK, VLAN tag push/swap is supported on IQ2 PICs and MX only

3/ 2nd method burns more IFL (subinterfaces in Cisco IOS speak) than 1st: you have to create units on physical interfaces and units on RVI interface.






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Posts: 1
Registered: ‎06-25-2010
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Re: VLAN on a logical unit interface or physical interface

You have to think of what would happen to your routing and your vlan when your physical interface goes down to.

I mean as an example

Vlan 1 on interface ge/0/0 to ge/0/03

Vlan 2 in ge0/0/4 to 6

IP address of vlan 1on ge/0/0/0

ge0/0/0 goes down, you could lose you route to vlan 2


An rvi is almost always up, not depending on one link