Multilink interfaces are used bond multiple PPP links to be used as a single link, this link will be represented by a virtual access. Multilink must be configured on the two ends of the circuit in order to work and they can be configured by multilink or interfaces or use a virtual-template configuration.

On the other hand virtual-templates are used to create virtual-access interfaces by cloning the virtual template configuration. For an example of using both, if we are configuring PPPoFR a virtual-template will be needed to create the PPP virtual-access interface dynamically, then if you have multiple PPPoFR that you want to bond together as a single link you will configure a multilink interface to represent the bond.

If this is still confusing let me know to try to communicate it better.

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thank you for your swift answer but doesn’t the virtual-template interface bind p2p interfaces too?

what you’re implying is that multilink interface is used when i’m connecting 2 routers with 2 or more serial interfaces and i want to bind them

but when a router is connected to a DSLAM for example and several different sources are needed to be binded, i use the virtual template

am i getting this right?

BTW.. you’re one of my heros

Thanks for your comment, The Multilink interface is another kind of logical interface with a single purpose which is to bind multiple PPP links together, the interface will be used as long as there are links up in the bond. The virtual-template for example in the case of PPPOE is used to create interface for each incoming user.

I hope I have clearly answered your question. Let me know if you are still confused.

your article is great but i want to know what is the difference between creating a MULTILINK interface and bind the physical interfaces to it versus creating a VIRTUAL-TEMPLATE interface with an ip unnumbered to a loopback to it?

is there difference in the way i should implement those and can you give me an example for each of those?

Typically virtual templates is used to provide Point to Point connections over different L2 technologies like PPPOA, PPPOE and PPPOFR. You do this when your implementation requires some of the PPP features like authentication of multilink.

virtual access may go down for any cause affecting any layer of communication between the end points. However, authentication and other PPP are common problems.

I hope your questions are answered

I have seen configs where the main WAN link say ADSL link ATM0, being bound to Virtual access interface. And also strange thing noticed is that if that Virtual access interface is in up down state, then other remote sites where not able to reach my site irrespective of WAN link staying UP, here I have few queries:

i) Why do we bound interfaces to Virtual access?

ii) when does the Virtual access go in UP/DOWN state?

Hearty request to see answers to my questions … Thanks for sharing your knowledge, Honestly speaking I have improved a lot reading posts here, continue the great work, may Almighty grant you guys a huge success