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Inline 6rd and 6to4 Softwires

Inline 6rd and 6to4 Configuration Guidelines

Keep the following points in mind when you are configuring and using inline 6rd and 6to4.

  • You can configure a maximum of 1024 softwire concentrators on a single line card.

  • Reassembly of 6rd IPv4 packet from CE is not added as part of this release.

  • 6rd multicast is not supported.

  • Any ICMPv4 errors generated in the IPv4 access network (between CPE and border relays) are dropped on the border relay. They are not converted into IPv6 errors and forwarded to IPv6 side.

  • 6rd/6to4 Anycast and load balancing can be configured only using next-hop style service-interface configuration, not interface style.

  • The si- interface input features are not exercised for packets flowing to the 6rd tunnel.

  • Bandwidth for traffic from the 6rd tunnel is limited by the available PFE bandwidth; bandwidth for traffic to the 6rd tunnel is limited by the internal VRF loopback bandwidth. SI-IFD loopback bandwidth configuration under the [edit chassis] hierarchy has no impact on the 6rd loopback bandwidth.

  • If the packet length is more than Tunnel MTU for downlink packets after encapsulating with an IPv4 header, the packet is dropped as v4 MTU errors. For these packet drops an ICMPv6 packet too big error message is sent back to the sender. Typically 6rd Tunnel MTU is configured with a high value so if the packet size is larger than the configured value, fragmentation occurs at the egress interface (towards the IPv4 access network).

Configuring Inline 6rd

Junos OS supports inline 6rd on all Modular Port Concentrator (MPC) line cards on MX Series routers. This saves customers the cost of using MS-DPCs for the required tunneling, encapsulation, and decapsulation processes. Anycast is supported for 6to4 (next-hop service interfaces only). Hairpinning is also supported for traffic between 6rd domains.

Junos OS supports inline 6rd on the following MPCs:

  • MPC5 and MPC6—Support starting in Junos OS Release 15.1R3.

  • MPC7, MPC8, and MPC9—Support starting in Junos OS Release 17.2R1.

  • MPC10E-15C-MRATE and MPC10E-10C-MRATE—Support starting in Junos OS Release 20.3R1.

  • MX2K-MPC11E—Support starting in Junos OS Release 20.3R1.

To implement the inline functionality, you configure service interfaces on the MPC as inline services interfaces (si-) rather than as multiServices (ms-) interfaces.

Configuring the Bandwidth for Inline Services

You must provide bandwidth configuration for inline services on the modular port concentrator (MPC) used for inline 6rd processing.

To configure bandwidth:

Specify the MPC and logical interface, and the desired bandwidth, 1g or 10g.

For example:

Configuring the Interfaces

Configure the si- interfaces for 6rd control and data. 6rd services must be configured on port 0.

To configure the si- interfaces:

  1. Configure the 6rd services on port 0 and include units for IPv4 and IPv6.

    For example:

  2. Configure the media interfaces for the inside service domain.

    For example:

  3. Configure the media interfaces for the outside service domain.

    For example:

  4. Configure the IPv4-facing interface for use with an interface-style or next-hop service set.
    • To configure for use with an interface-style service set, configure input and output service and specify the service set.

      For example:

    • To configure for use with a next-hop style service set, omit the service input and service output references.

      For example:

  5. Configure the IPv6 facing interface.

    For example:

Configuring the Softwire Concentrator and Rule

Define the softwire concentrator and rule used for encapsulation and decapsulation of IPv6 over IPv4 packets for CE.

To define the softwire concentrator:

  1. Specify a 6rd softwire concentrator and its address.

    For example:

  2. Configure the IPv4 address prefix for the customer edge network and the IPv6 address prefix for the 6rd domain.

    For example:

  3. Configure the size, in bytes, of the maximum transmission unit mtu-ipv4 for IPv6 packets encapsulated in IPv4. Compute this as the maximum expected IPv4 packet size plus 20.

    For example:

To configure the softwire rule:

  • Specify the softwire rule, specifying the direction of traffic to be tunneled and the 6rd softwire concentrator to be used.

    For example:

Configuring the Service Set

To configure an interface style or next-hop service set for 6rd processing:

  • Specify an interface style service set.

    For example:


  • Configure a next-hop service set.

Configuring the Routing Instance

To configure the routing instance:

  1. Specify the routing instance and each interface it serves.

    For example:

  2. Specify the route distinguisher and vrf-target.

Examples: 6rd and 6to4 Configurations


The 6rd and 6to4 features are supported on Multiservices 100, 400, and 500 PICs on M Series routers, and on MX Series routers equipped with Multiservices DPCs. MX Series routers with MS-MPCs or MS-MICs support inline 6rd and inline 6to4 features.

Example: 6rd with Interface-Style Service Set Configuration

Example: 6rd with Next-Hop-Style Service Set Configuration

Example: 6rd Anycast Configuration

Example: Hairpinning Between 6rd Domains Configuration

This example uses an interface service-set and a next-hop service set as hairpinning domains.

Example: 6to4 Configuration