Tunnel interfaces (Inline) on MX Trio based line cards

This article provides information on Tunnel interfaces that can be created Inline on MX Trio based line cards. Tunnel services are a collection of encapsulation and decapsulation logical interfaces that are used for forwarding traffic in certain scenarios. On platforms prior to MX, a special Tunnel PIC was required to enable these tunnel service interfaces. With the Trio-based line cards, the tunnel services are built into each PFE and there is no loss of physical ports meant for forwarding traffic. Since the tunnel service processing happens directly on the line card, the performance is near line-rate and keeps the latency to a minimum.

Tunnel interfaces are used for a variety of applications in JunOS. They provide the ability to do a second forwarding table lookup after a packet has been encapsulated for entry into a tunnel or decapsulated after exiting a tunnel.

The following are most common tunnel types supported in JunOS :

GRE Tunnels: Generic Routing Encapsulation (GRE) is a tunneling protocol that can encapsulate multiple network layer protocol packet types inside IP tunnels, creating a virtual point-to-point link to routers at remote points over an IP network. The interface name for GRE tunnels is "gr-"

PIME/PIMD Tunnels: Protocol Independent Multicast (PIM) tunneling is a way of tunneling IP multicast traffic inside unicast IP tunnels from the DR connected to the source to the Rendezvous Point (RP) over an IP network. The DR uses the "pime" interface to encapsulate and the RP uses the "pimd" interface for the encapsulation and decapsulation of the PIM Register messages.

Multicast (MT) Tunnels: Multicast tunneling used in Rosen MVPN scenarios is based on GRE that can encapsulate multiple customer multicast traffic inside IP Multicast tunnels in the service provider network. Th "mt-" interfaces are required on the Rosen MVPN PE devices for encapsulation and decapsulation of the customer multicast traffic.

VT Tunnels: Virtual loopback tunneling (VT) is used to support VRF (multi-protocol) lookup based on result of MPLS lookup. This "vt-" interface can be used in L3VPN and VPLS scenarios on the PE devices.

LT Tunnels: Logical tunneling (LT) is used to support point-to-point connectivity between logical systems. The "lt-" interface can be used for interconnecting different VRFs or logical systems on the same physical router.

IP-IP Tunnels: IPIP tunneling is similar to GRE tunneling except that there is no GRE header between inner IP and outer IP headers. Hence, it will encapsulate only IP packets instead of encapsulating multi- protocol payloads. The interface name for IP tunnels is "ip-"

Sample configuration to enable inline tunnel services on FPC 2 PIC 0:

chassis {
    fpc 2 {
        pic 0 {
            tunnel-services {
                bandwidth 10g;
            }
        }
    }
}

lab@rtr-> show interfaces terse | match 2/0/0 
gr-2/0/0                up    up < --  GRE
ip-2/0/0                up    up < -- IPIP
lt-2/0/0                up    up < -- Logical tunnel
mt-2/0/0                up    up < -- Multicast tunnel
pd-2/0/0                up    up < -- PIM decap
pe-2/0/0                up    up < -- PIM encap
vt-2/0/0                up    up < -- Virtual tunnel
xe-2/0/0                up    up < -- Physical interface

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