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Cisco 10000 Series Router Software Configuration Guide
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Chapter 22 Configuring Multilink Point-to-Point Protocol Connections
How MLP Determines the Link a Bundle Joins
MLP Group Interfaces and Virtual Template Interfaces
You can configure MLP by assigning a multilink group to a virtual template interface configuration.
Virtual templates allow a virtual access interface (VAI) to dynamically clone interface parameters from
the specified virtual template. If you assign a multilink group to a virtual template and you assign the
virtual template to a physical interface, all of the links that pass through the physical interface belong to
the same multilink bundle.
A multilink group interface configuration overrides a global multilink virtual template configured using
the
multilink virtual template
command.
On the Cisco 10008 router, you can use multilink group interfaces with ATM and serial interfaces. To
configure MLP using a multilink group interface, do the following:
•
Configure the multilink group under the ATM PVC or any other interface.
•
Assign the ppp multilink to a virtual template.
•
Configure the physical interface to use the virtual template.
For more information, see the
“Changing the Default Endpoint Discriminator” section on page 22-37
.
How MLP Determines the Link a Bundle Joins
A link joins a bundle when the identification keys for that link match the identification keys for an
existing bundle.
Two keys define the identity of a remote system: the PPP username and the MLP endpoint discriminator.
The PPP authentication mechanisms (for example, PAP or CHAP) learn the PPP username. The endpoint
discriminator is an option negotiated by the Link Control Protocol (LCP). Therefore, a bundle consists
of all of the links that have the same PPP username and endpoint discriminator.
A link that does not provide a PPP username or endpoint discriminator is an anonymous link. MLP
collects all of the anonymous links into a single bundle referred to as the anonymous bundle or default
bundle. Typically, there can be only one anonymous bundle. Any anonymous links that negotiate MLP
join (or create) the anonymous bundle.
When using multilink group interfaces, more than one anonymous peer is allowed. When you preassign
a link to an MLP bundle by using the
ppp multilink group
command, and the link is anonymous, the
link joins the bundle interface it is assigned to if the interface is not already active and associated with
a nonanonymous user.
MLP determines the bundle a link joins in the following steps:
1.
When a link connects, MLP creates a bundle name identifier for the link.
2.
MLP then searches for a bundle with the same bundle name identifier.
–
If a bundle with the same identifier exists, the link joins that bundle.
–
If a bundle with the same identifier does not exist, MLP creates a new bundle with the same
identifier as the link, and the link is the first link in the bundle.
Table 22-2
describes the commands and associated algorithm used to generate a bundle name. In the
table, “username” typically means the authenticated username; however, an alternate name can be used
instead. The alternate name is usually an expanded version of the username (for example, VPDN tunnels
might include the network access server name) or a name derived from other sources.
