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Juniper MX Series by Harry Reynolds, Douglas Richard Hanks Jr.

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Tunnel Services

Junos makes working with encapsulation very easy and straightforward. Tunnel services are a collection of encapsulation and decapsulation logical interfaces that are used to help forward traffic. The types of tunnel services supported are as follows:

IP Tunnel (IPIP)

IPIP is a very basic IP tunneling protocol that simply encapsulates the original packet in a new IP header. The interface name for IPIP in Junos is “ip-.”

Generic Routing Encapsulation (GRE)

GRE improves upon IPIP and adds the ability to enforce packet sequencing, specify tunnel keys, and encapsulation any Layer 3 protocol without being limited to only IP. The interface name for GRE in Junos is “gr-.”

Logical Tunnels

Logical tunnels are pseudointerfaces in Junos; they look and feel like regular interfaces, but don’t consume any physical ports. A common use case is to use a logical tunnel to interconnect two VRFs. The interface name for logical tunnels in Junos is “lt-.”

Protocol Independent Multicast (PIM) Encapsulation and Decapsulation

These interfaces are used by PIM designated routers (DR) or rendezvous points (RP) to encapsulate and decapsulate packets during the PIM JOIN and REGISTER processes. The interface names for PIM encapsulation and decapsulation in Junos are “pe-” and “pd-.”

In previous platforms, a special Tunnel PIC was required to enable these interfaces. The DPC line cards also required that a single 10 G port be disabled when using tunnel services; however, with the Trio-based line cards, the ...

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