# Supported MLPPP Features

The router currently supports both the static configuration of the links participating in a multilink bundle and the dynamic creation of MLPPP bundles over L2TP (only on the LNS) when the LNS detects multilink LCP option negotiation in LCP proxy data.

The following MLPPP features are available for both static and dynamic MLPPP:

- Logical aggregation of up to eight links in a bundle
- Long sequence numbers
- Authentication for interfaces with MLPPP encapsulation or for MLPPP bundles
- Monotonically increasing sequence numbers

  All packets distributed across the member links have monotonically increasing sequence numbers. This feature enables the remote system on the customer premises to perform resequencing (if the system is configured to do so).

- Round-robin packet distribution or hash-based packet distribution

  By default, E Series routers use a round-robin algorithm to handle packet distribution across the member links in a bundle for both best-effort traffic and non-best-effort traffic. The round-robin approach is used even when the member links have different line rates.

  As an alternative to round-robin packet distribution for non-best-effort traffic, you can enable use of a hash-based algorithm for distribution of non-best-effort (high-priority) packets, such as voice or video. Using a hash-based packet distribution mechanism instead of the default round-robin packet distribution mechanism for non-best-effort traffic ensures that the router maintains the proper packet order when transmitting high-priority packets. For details, see MLPPP Link Selection.

- Forwarding of multilink traffic to L2TP tunnels

  E Series routers support dynamic MLPPP over L2TP configurations (on the L2TP network server, or LNS).

- Fragmentation and reassembly

  For details, see Configuring MLPPP Fragmentation and Reassembly.

- Packet resequencing for best-effort traffic, for non-best-effort traffic, and when MLPPP reassembly is enabled

  For details on how the router supports packet resequencing for best-effort traffic and non-best-effort traffic, see MLPPP Link Selection.

  For details on enabling MLPPP reassembly, see Configuring MLPPP Fragmentation and Reassembly.

- Multiclass MLPPP

  For information about multiclass MLPPP, see Configuring Multiclass Multilink PPP.

You can configure bundles as follows:

- On a COCX-F3 line module and its corresponding I/O modules, you can configure:
  - Up to 8 member links from different ports in the same bundle, with the following restriction for MLPPP reassembly:
    - For a COCX-F3 line module with either a 12-port E3-12 FRAME I/O module or a 12-port CT3/T3 12 I/O module, the restriction is based on the ports on which member links in the same bundle are configured.

      A 12-port E3-12 FRAME I/O module and a 12-port CT3/T3 12 I/O module each contain 12 ports numbered 0 through 11. When MLPPP reassembly is enabled, you can configure a bundle with member links on the same port; on ports 0, 1, and 2; on ports 3, 4, and 5; on ports 6, 7, and 8; or on ports 9, 10, and 11. However, the router cannot properly reassemble fragments if you configure a bundle with member links that span ports in different bundles; for example, on ports 0, 1, and 4.

      When MLPPP reassembly is disabled, this restriction is not in effect; that is, member links can span ports in different bundles.

  - Up to 12 bundles
- On a cOCx/STMx line module and its corresponding I/O module, you can configure:
  - Member links from different OC3/STM1 ports in the same bundle, with the following restrictions for MLPPP reassembly:
    - For a cOCx/STMx line module with a 4-port cOC3/STM1 I/O module, the restriction is based on the ports on which member links in the same bundle are configured.

      A 4-port cOC3/STM1 I/O module contains four ports numbered 0 through 3. When MLPPP reassembly is enabled, you can configure a bundle with member links on the same port, on ports 0 and 1, or on ports 2 and 3. However, the router cannot properly reassemble fragments if you configure a bundle with member links that span ports in different bundles; for example, on ports 1 and 2.

      When MLPPP reassembly is disabled, this restriction is not in effect; that is, member links can span ports in different bundles.

    - For a cOCx/STMx line module with a 1-port cOC12/STM4 I/O module, the restriction is based on the STM1 (OC3) paths on which member links in the same bundle are configured.

      A 1-port cOC12/STM4 I/O module has four logical paths numbered 1 through 4. When MLPPP reassembly is enabled, you can configure a bundle with member links on the same path, on paths 1 and 2, or on paths 3 and 4. However, the router cannot properly reassemble fragments if you configure a bundle with member links that span paths in different bundles; that is, on paths 2 and 3.

      When MLPPP reassembly is disabled, this restriction is not in effect; for example, member links can span paths in different bundles.

  - Any combination of bundles that does not exceed the 336 available T1 channels (for example, 336 single-link T1 bundles, 42 eight-link bundles, or 41 eight-link bundles and 8 single-link bundles)
  - Any combination of bundles that does not exceed the 252 available E1 channels (for example, 252 single-link T1 bundles, 34 eight-link bundles, or 33 eight-link bundles and 8 single-link bundles)
- On a CT3/T3-F0 line module with a CT3/T3 12 I/O module, you can configure:
  - Member links from different T3 ports in the same bundle
  - Any combination of bundles that does not exceed the 336 available T1 channels (for example, 336 single-link T1 bundles, 42 eight-link bundles, or 41 eight-link bundles and 8 single-link bundles)
- On an ES2-S1 Service IOA, you can configure:
  - Up to 16,000 member links per line module, not to exceed a total of 12,000 MLPPP bundles per chassis
  - Any combination of bundles that does not exceed either of these maximums (for example, 4000 single-link bundles, 4000 two-link bundles, 4000 four-link bundles, and 2000 eight-link bundles)
- On an OCx/STMx ATM line module and its corresponding line modules, you can configure:
  - Up to 8000 member links per line module, not to exceed a total of 8000 MLPPP bundles per chassis
  - Any combination of bundles that does not exceed either of these maximums (for example, 4000 single-link bundles, 4000 two-link bundles, 2000 four-link bundles, and 1000 eight-link bundles)
- On a Service line module (SM), you can configure:
  - Up to 16,000 member links per line module, not to exceed a total of 12,000 MLPPP bundles per chassis
  - Any combination of bundles that does not exceed either of these maximums (for example, 4000 single-link bundles, 4000 two-link bundles, 4000 four-link bundles, and 2000 eight-link bundles)
- On a shared tunnel-server port configured on a GE-2 or GE-HDE line module and corresponding line modules, you can configure:
  - Up to 8000 member links per line module, not to exceed a total of 8000 MLPPP bundles per chassis
  - Any combination of bundles that does not exceed either of these maximums (for example, 4000 single-link bundles, 4000 two-link bundles, 2000 four-link bundles, and 1000 eight-link bundles)
- On an ES2-S1 GE-4 IOA, ES2-S1 GE-8 IOA, ES2-S1 OC3-8 STM1 ATM IOA, and ES2-S1 OC12-2 STM4 ATM IOA modules that pair with an ES2 4G LM on E120 and E320 routers, you can configure:
  - MLPPP bundles with one or more links per bundle for dynamic MLPPP-over-PPPoE-over-Ethernet configurations.
  - MLPPP bundles with only one link per bundle when configuring static MLPPP-over-PPPoE-over-Ethernet. When you create multilink bundles in a static MLPPP-over-PPPoE-over-Ethernet configuration, PPPoE is unable to direct the PPPoE Active Discovery Initiation (PADI) packets received from the MLPPP bundle links on the client to the appropriate (matching) links in the MLPPP bundle on the server. As a result, the connections between bundle links become crossed, and the bundle does not come up as expected. Creating MLPPP bundles with only a single link for this configuration ensures a one-to-one correspondence between a PPPoE subscriber and its associated link, and guarantees that the MLPPP bundle comes up properly.
  - MLPPP bundles with only a single link per bundle are not required for static MLPPP-over-PPPoE-over-Ethernet with VLAN configurations if all of the links in a bundle have the same VLAN ID that is unique across all MLPPP bundles configured on the line module.
- On all E Series ATM module combinations that support MLPPP, you can configure:
  - MLPPP bundles with one or more links per bundle for dynamic MLPPP-over-multiple PPPoE subinterfaces-over-one PPPoE major interface-over-ATM 1483 subinterface configurations.
  - MLPPP bundles with only one link per bundle when configuring static MLPPP-over-multiple PPPoE subinterfaces-over-one PPPoE major interface-over-an ATM 1483 subinterface. In this configuration, you can stack multiple PPPoE subinterfaces over a single PPPoE major interface.
  - Typically when you create ATM PVCs on an ATM module, there is a one-to-one correspondence between a PPPoE subscriber and the ATM PVC with which the subscriber is associated. However, in configurations with multiple PPPoE subinterfaces stacked over a single PPPoE major interface, crossed MLPPP bundle link connections can occur, as is the case with the ES2-S1 GE-4 IOA, and the bundle does not come up as expected. Creating MLPPP bundles with only a single link for this configuration ensures a one-to-one correspondence between a PPPoE subscriber and its associated link, and guarantees that the MLPPP bundle comes up properly.
  - MLPPP bundles with only a single link per bundle are not required for static MLPPP-over-multiple PPPoE subinterfaces-over-one PPPoE major interface-over-ATM 1483 subinterface configurations if all PPPoE subinterfaces stacked over the same PPPoE major interface belong to the same bundle.

    | Note: For information about the modules that support MLPPP on ERX14xx models, ERX7xx models, and the ERX310 router, see ERX Module Guide, Appendix A, Module Protocol Support. For information about the modules that support MLPPP on the E120 and E320 routers, see E120 and E320 Module Guide, Appendix A, IOA Protocol Support.

- IPv6 Neighbor Discovery router advertisements are supported for multilink PPP interfaces when a multilink PPP bundle between the subscriber and the PPP server running on the router uses IPv6 for data transmission. When an IPv6 interface is stacked on a multilink PPP bundle, the delegating router allocates IPv6 prefixes to the requesting routers. The router uses ICMPv6 Neighbor Discovery router advertisements to respond to route solicitation packets it receives from the subscriber.