Juniper JUNOSE 11.2.X MULTICAST ROUTING, Configuration Manual

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This section describes the redundancy and interface distribution mechanisms for all
tunnel-server ports.
SMs, ES2-S1 Service IOA, and Shared Tunnel-Server Modules
You can install multiple modules to provide redundancy. If you install multiple modules
at the same time, the router automatically distributes the tunnel-service interfaces over
the modules in proportion to the available tunnel-service interfaces. Both the primary
and the redundant line modules must provide identical functionality. For instance, if the
primary line module provides forwarding functionality, you cannot configure the redundant
line module to provide shared tunnel-server functionality. Similarly, if the primary line
module provides shared tunnel-server functionality, you cannot configure the redundant
line module to provide forwarding functionality.
NOTE: Shared tunnel server on the ES2 10G ADV LM supports line module redundancy.
Even distribution of tunnel-service interfaces is not critical to router performance. However,
the number of modules that you install must be able to support the extra tunnel if one
of the modules becomes unavailable.
NOTE: When both dedicated tunnel-server ports (on SMs) and shared tunnel-server
ports (on shared tunnel-server modules) are configured on ERX7xx models, ERX14xx
models, and the ERX310 router, the router performs load balancing across all available
server ports of the same type. For this purpose, dedicated tunnel-server ports (on SMs)
and shared tunnel-server ports (on shared tunnel-server modules) are considered one
type of server port, whereas server ports on ISMs are considered a different type.
Interface allocation depends on the types of tunnel-service interface created on the
router. For more information about the types of tunnel-service interfaces, see “Types of
Tunnel-Service Interfaces” on page 208
.
Static IP Tunnel-Service Interfaces
You can configure and delete static IP tunnel-service interfaces.
When you configure a static tunnel-service interface, the router automatically assigns
that interface to a particular module. If that module becomes unavailable, the router
attempts to reassign the interface to an available module. If no module is currently
available, the router keeps track of the interface and assigns it to a module when one
become available.
Consequently, if you reinstall a module that was formerly unavailable or removed, the
distribution of static tunnel-service interfaces over the modules might be uneven. Because
users create and remove static tunnels, the distribution might remain uneven indefinitely.
Dynamic Tunnel-Service Interfaces
The router dynamically creates and deletes dynamic tunnel-service interfaces as dictated
by the operation of the relevant protocols. Currently, L2TP sessions are the only dynamic
tunnel-service interfaces available.
213 Copyright © 2010, Juniper Networks, Inc.
Chapter 6: Managing Tunnel-Service and
IPSec-Service Interfaces