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Configuring Layer 2 Circuits

To implement Layer 2 circuits, perform the following:

Configuring an Interface Encapsulation on CE-Facing Interfaces

When you configure Layer 2 circuits, you can use Ethernet, SONET/SDH, and ATM2 IQ interfaces on a PE router. The specific steps you must take to configure these interface types for Layer 2 circuits are described as follows:

Configuring CCC Encapsulation on CE-Facing Ethernet Interfaces

On Ethernet-based CE-facing PE router interfaces, you must configure one of the three Ethernet CCC encapsulation types—Ethernet CCC, VLAN CCC, or Extended VLAN CCC. Use the following guidelines to configure an Ethernet-based interface CCC encapsulation:

For more information about VLAN IDs, see “Binding a VLAN ID to a Logical Interface” in the JUNOS Network Interfaces Configuration Guide.

To configure CCC interface encapsulation, include the encapsulation statement at the [edit interfaces ethernet-interface-fpc/pic/port] hierarchy level and select ethernet-ccc, vlan-ccc, or extended-vlan-ccc as the encapsulation type. If you select the VLAN CCC encapsulation, also include the vlan-ccc statement at the [edit interfaces ethernet-interface-fpc/pic/port unit unit-number encapsulation] logical interface hierarchy level. When using either VLAN CCC or extended VLAN CCC encapsulations, include the vlan-tagging statement at the [edit interfaces ethernet-interface-fpc/pic/port] hierarchy level.

[edit]
interfaces {
fe-0/1/0 {
vlan-tagging;
encapsulation vlan-ccc;
unit 0 {
encapsulation vlan-ccc;
vlan-id 600;
}
}
}

Configuring CCC Encapsulation on CE-Facing SONET/SDH Interfaces

On SONET/SDH interfaces in a PE router, you can use Frame Relay CCC, Cisco HDLC CCC, or PPP CCC encapsulation for Layer 2 circuits:

Configuring a CCC Encapsulation and a Layer 2 Circuit Mode on CE-Facing ATM2 IQ Interfaces

On ATM2 IQ interfaces in a PE router, you need to configure two encapsulations to enable Layer 2 circuits: one at the [edit interfaces at-fpc/pic/port] hierarchy level and the other at the [edit chassis fpc fpc-slot pic pic-slot] hierarchy level. There are two types of ATM2 IQ Layer 2 circuits: cell-relay mode and ATM Adaptation Layer 5 (AAL5) mode. For both modes, you must specify the Physical Interface Card (PIC) type with the pic-type atm2 statement at the [edit interfaces at-fpc/pic/port atm-options] hierarchy level. You can configure only one mode per PIC at a time. If you need to enable both ATM2 IQ Layer 2 circuit modes in the same router, you must configure the different modes on different PICs.

To configure a cell-relay mode Layer 2 circuit, include the atm-l2circuit-mode cell statement at the [edit chassis fpc fpc-slot pic pic-slot] hierarchy level and the encapsulation atm-ccc-cell-relay statement at both the [edit interfaces at-fpc/pic/port] physical hierarchy level and the [edit interfaces at-fpc/pic/port unit unit-number] logical interface hierarchy level.

[edit]
chassis {
fpc 0 {
pic 1 {
atm-l2circuit-mode {
cell;
}
}
}
}
interfaces {
at-0/1/0 {
encapsulation atm-ccc-cell-relay;
atm-options {
cell-bundle-size 4;
pic-type atm2;
vpi 0;
}
unit 0 {
encapsulation atm-ccc-cell-relay;
vci 32;
cell-bundle-size 10;
}
}
}

For ATM2 IQ Layer 2 circuit cell-relay mode only, you can adjust the cell bundle size at the physical interface level and the logical interface level. To configure, include the cell-bundle-size statement at either the [edit interfaces at-fpc/pic/port atm-options] physical interface hierarchy level or the [edit interfaces at-fpc/pic/port unit unit-number] logical interface hierarchy level. If the statement is included at both levels, the logical interface setting takes precedence. The default value for cell bundle size is 1 and the maximum value is 190. If you configure the cell bundle size statement, you should configure the same value on all ATM2 IQ neighbors.

To configure an AAL5 mode Layer 2 circuit, include the atm-l2circuit-mode aal5 statement at the [edit chassis fpcfpc-slot pic pic-slot] hierarchy level and the encapsulation atm-ccc-vc-mux statement at the [edit interfaces at-fpc/pic/port] hierarchy level:

[edit]
chassis {
fpc 1 {
pic 2 {
atm-l2circuit-mode {
aal5;
}
}
}
}
interfaces {
at-1/2/0 {
atm-options {
pic-type atm2;
vpi 0;
}
unit 0 {
encapsulation atm-ccc-vc-mux;
vci 32;
}
}
}

For more information on how to configure interfaces with CCC encapsulation types, see the JUNOS MPLS Applications Configuration Guide or the JUNOS Network Interfaces Configuration Guide.

Configuring the MPLS Family on Core Interfaces

Because LDP is used as the signaling protocol to transport MPLS labels across the core of the network, you must include the family mpls statement at the [edit interfaces interface-name unit logical-unit-number] hierarchy level. Include the statement on all router interfaces in the path from the local PE router to the remote PE router across the core network that transports the Layer 2 circuit traffic.

[edit]
interfaces {
interface-name {
unit logical-unit-number {
family inet {
address ip-address/prefix;
}
family mpls;
}
}
}

Configuring Layer 2 Circuits

After you enable the PE router interfaces with the proper encapsulations, you then configure Layer 2 circuits (also referred to as VCs) between two or more PE router neighbors. To configure a Layer 2 circuit, include the l2circuit statement at the [edit protocols] hierarchy level.

Each Layer 2 circuit is represented by a logical interface on the local PE router, the IP address of the remote PE router neighbor, and a virtual circuit identifier. The logical interface connects the local PE router to the local CE router. The loopback address and router ID of the PE neighbor is commonly the neighbor’s IP address. This address is also the destination end-point of the LSP tunnel, which transports the Layer 2 circuit to the neighbor. The virtual circuit ID uniquely identifies the VC to a specific neighbor.

This combination of logical interface, neighbor address, and virtual circuit ID is used to map a particular LDP forwarding equivalence class (FEC) received from a specific neighbor to a local VC. The egress label is added to a table and is used for sending traffic on that VC between the CE routers.

Both ends of a Layer 2 circuit must use the same Layer 2 technology because the Layer 2 encapsulation type is carried in the LDP FEC. The encapsulation type from a received FEC is matched against the local encapsulation type of the VC. If there is a mismatch, the VC is not established.

To add the IP address of the remote PE router neighbor into a Layer 2 circuit, include the neighbor ip-address statement at the [edit protocols l2circuit] hierarchy level. To map the remote neighbor to the local interface that connects to the CE router, include the interface statement at the [edit protocols l2circuit neighbor ip-address] hierarchy level. To select the identifier for the virtual circuit, include the virtual-circuit-identifier statement at the [edit protocols l2circuit neighbor ip-address interface interface-name] hierarchy level. To disable default control word processing, include the no-control-word statement at the [edit protocols l2circuit neighbor ip-address interface interface-name] hierarchy level. Finally, to assign the Layer 2 circuit to a community, include the community community-namestatement at the [edit protocols l2circuit neighbor ip-address interface interface-name] hierarchy level.

Note: On M-series routing platforms only, if you include the control-word statement at the [edit protocols l2circuit neighbor address interface interface-name] hierarchy level (the default setting for Layer 2 circuits), the software cannot rewrite MPLS EXP bits.

[edit]
protocols {
l2circuit {
traceoptions {
file name [replace] [size size] [files files ] [nostamp];
flag (error | topology | nlri | connections | route) [detail];
}
neighbor ip-address {
interface interface-name {
virtual-circuit-id identifier;
no-control-word;
community community-name;
}
}
}
}

You do not need to specify the encapsulation type at the [edit protocols l2circuit] hierarchy level because it is already specified in the interface configuration.

Configuring LDP and an IGP to Transport Layer 2 Circuits

LDP is used as the signaling protocol to advertise the ingress MPLS label to the remote PE router. For this purpose, a remote LDP neighbor is established using the extended discovery mechanism described in RFC 3036, LDP Specification, and a session is established.

No new configuration is necessary in LDP because the LDP protocol recognizes the Layer 2 circuit configuration and initiates extended neighbor discovery for all Layer 2 circuit neighbors on the remote PE routers. This is very similar to the behavior of LDP when it is tunneled over RSVP. However, you must configure LDP on the lo0.0 interface for extended neighbor discovery to function correctly.

LDP relies on an underlying IGP, such as OSPF or IS-IS. Therefore, configure LDP and your IGP on all routers in the path from the local PE router to the remote PE router across the service provider backbone.

[edit]
protocols {
ospf {
traffic-engineering;
area 0.0.0.0 {
interface so-0/1/0.0;
interface lo0.0;
}
}
ldp {
interface so-0/1/0.0;
interface lo0.0;
}
}

Option: Applying Traffic Engineering to a Layer 2 Circuit

To traffic engineer Layer 2 circuits over multiple LSPs, you must create a community, assign a set of Layer 2 circuits to that community, define a policy to send the community traffic over a desired LSP, and apply the policy to the forwarding table.

To create a community, include the community community-name statement at the [edit policy-options] hierarchy level. To assign a Layer 2 circuit to a community, include the community community-name statement at the [edit protocols l2circuit neighbor ip-address interface interface-name] hierarchy level. To create a policy that sends community traffic over a specific LSP, include the community community-namestatement at the [edit policy-options policy-statement policy-name term term-name from] hierarchy level and the install-next-hop lsp lsp-name statement at the [edit policy-options policy-statement policy-name term term-name then] hierarchy level. To apply the policy to the forwarding table, include the export policy-name statement at the [edit routing-options forwarding-table] hierarchy level.

[edit]
routing-options {
forwarding-table {
export policy-name;
}
}
protocols {
l2circuit {
neighbor ip-address {
interface interface-name {
virtual-circuit-id identifier;
community community-name;
}
}
}
}
policy-options {
policy-statement policy-name {
from community community-name;
then {
install-nexthop lsp lsp-name;
accept;
}
}
}
community community-name members value;

Option: Mapping Layer 2 Protocol Control Information into a Layer 2 Circuit

The control word is defined in Internet draft draft-martini-l2circuit-encap-mpls-07.txt Encapsulation Methods for Transport of Layer 2 Frames Over IP and MPLS Networks. It is a set of fields that carry Layer 2 control information across a Layer 2 circuit. The following control word support is available for PE routers:

Option: Configuring APS for Layer 2 Circuits

To apply Automatic Protection Switching (APS) to a Layer 2 circuit, you must configure an APS working circuit and a protect circuit on PE router interfaces that support SONET options (such as SONET/SDH, ATM, and ATM2 IQ interfaces) and circuit cross-connect (CCC) encapsulation types. Then, you must configure the working circuit as the primary Layer 2 circuit interface and the protect circuit as the protected Layer 2 circuit interface. Note that APS only protects the PE-CE link and not the entire Layer 2 circuit.

To configure an APS working circuit, include the working-circuit statement at the [edit interfaces interface-name sonet-options aps] hierarchy level. To configure an APS protect circuit, include the protect-circuit statement at the [edit interfaces interface-name sonet-options aps] hierarchy level. To configure the primary Layer 2 circuit interface, include the interface statement at the [edit protocols l2circuit neighbor ip-address] hierarchy level. To configure the protected Layer 2 circuit interface, include the protect-interface statement at the [edit protocols l2circuit neighbor ip-address interface interface-name] hierarchy level.

[edit]
interfaces {
at-0/0/1 {
description “ APS protect circuit”;
encapsulation CCC-encapsulation-type;
sonet-options {
aps {
protect-circuit name;
}
}
}
at-1/3/1 {
description “APS working circuit”;
encapsulation CCC-encapsulation-type;
sonet-options {
aps {
working-circuit name;
}
}
}
}
protocols {
l2circuit {
neighbor ip-address {
interface at-1/3/1.0 {
protect-interface at-0/0/1.0;
virtual-circuit-id number;
}
}
}
}

Option: Configuring Layer 2 Circuit Trunk Mode on ATM2 IQ Interfaces

When you configure Layer 2 circuits on CE-facing ATM2 IQ interfaces in a PE router that connects to some vendors’ ATM switches, you can create a trunk. The trunk bundles several ATM cell streams into one LSP, preserves the cell loss priority (CLP) and class-of-service (CoS) information of the cells within the experimental (EXP) bits of the MPLS header, and provides network-to-network interface (NNI) or user-to-network interface (UNI) information within a proprietary header. A physical interface supports a total of 32 logical trunks in NNI mode and 8 logical trunks when you use the UNI option. To configure a trunk, include the trunk statement at the [edit chassis fpc fpc-slot pic pic-slot atm-l2circuit-mode] hierarchy level, select NNI or UNI mode with the nni or uni statement, and specify a number of bits in the ATM header that will carry an identifier with the id-width statement. You can choose a value from 1 through 8 for the identifier width.

[edit]
chassis {
fpc fpc-slot {
pic pic-clot {
atm-l2circuit-mode {
trunk {
(nni | uni) {
id-width number;
}
}
}
}
}
}

You can also configure several trunk options at the [edit interfaces at-fpc/pic/port unit unit-number] hierarchy level:

You can configure a variety of CoS-related statements for an ATM2 IQ interface-based scheduler map. To select the CoS mode used for virtual circuits, include the vc-cos-mode statement at the [edit interfaces at-fpc/pic/port atm-options scheduler-maps map-name] hierarchy level. To specify forwarding class settings, include the priority, transmit-weight, and epd-threshold statements at the [edit interfaces at-fpc/pic/port atm-options scheduler-maps map-name forwarding-class class-name] hierarchy level. For more information about CoS, see the JUNOS Class of Service Configuration Guide.

[edit]
interfaces {
at-fpc/pic/port {
atm-options {
pic-type atm2;
scheduler-maps {
map-name {
vc-cos-mode (alternate | strict);
forwarding-class class-name {
priority (high | low);
transmit-weight (cells number-of-cells | percent percentage);
epd-threshold plp0-threshold plp1 plp1-threshold;
}
}
}
}
}
}

Option: Reserving LSP Bandwidth for a Layer 2 Circuit

You can specify the amount of bandwidth in bytes per second that must be available on an LSP for a specific Layer 2 circuit. By using a bandwidth constraint for a Layer 2 circuit, the router performs a type of call admission control. If an LSP exists that contains the required bandwidth, the Layer 2 circuit is established. If the bandwidth is not available on an LSP, the Layer 2 circuit is not established.

To configure bandwidth requirements for a Layer 2 circuit, include the bandwidth statement at the [edit protocols mpls label-switched-path lsp-name] hierarchy level and the [edit protocols l2circuit neighbor ip-address interface interface-name] hierarchy level.

[edit]
protocols {
mpls {
label-switched-path lsp-name {
bandwidth traffic-class bytes-per-second;
}
}
l2circuit {
neighbor ip-address {
interface interface-name {
bandwidth bytes-per-second;
}
}
}
}

You can also assign minimum bandwidth requirements for class-of-service (CoS) queues within a Layer 2 circuit and its corresponding LSP. Class type (CT) queues 0, 1, 2, and 3 in a Layer 2 circuit or LSP correspond to the standard four CoS queues available on M-series, MX-series, and T-series routing platforms. To enable mapping of class type queues to the standard CoS queues, include the bandwidth-model statement at the [edit protocols mpls diffserv-te] hierarchy level. To assign specific bandwidth requirements to each class type queue, include the ct0, ct1, ct2, and ct3 statements at the [edit protocols mpls label-switched-path lsp-name bandwidth] hierarchy level and the [edit protocols l2circuit neighbor ip-address interface interface-name bandwidth] hierarchy level.

[edit]
protocols {
mpls {
diffserv-te {
bandwidth-model extended-mam;
}
label-switched-path lsp-name {
bandwidth {
ct0 100m;
ct1 100m;
ct2 50m;
ct3 5m;
}
}
}
l2circuit {
neighbor ip-address {
interface interface-name {
bandwidth {
ct0 100m;
ct1 100m;
ct2 50m;
ct3 5m;
}
}
}
}
}

For more information about class of service, see the JUNOS Class of Service Configuration Guide.

Option: Selecting an MTU for a Layer 2 Circuit

To configure the MTU for each individual Layer 2 circuit, include the mtu statement at the [edit protocols l2circuit neighbor ip-address interface interface-name] hierarchy level. If the MTU setting between Layer 2 circuit neighbors does not match, the Layer 2 circuit is torn down.

Note: If you configure an MTU value for an ATM cell relay interface on an ATM2 PIC and simultaneously configure an MTU value for a Layer 2 circuit that uses the same ATM2 PIC, the MTU value for the Layer 2 circuit takes precedence when calculating the cell bundle size and is advertised to Layer 2 circuit neighbors.

Option: Configuring Local Interface Switching for a Layer 2 Circuit

You can terminate a Layer 2 circuit locally on an ingress PE router. To configure a locally terminated circuit, include the local-switching statement at the [edit protocols l2circuit] hierarchy level. Select the Layer 2 circuit interfaces you want to connect locally, specify any APS protect interfaces, and configure an end interface. To select the Layer 2 circuit interfaces that are connected locally, include the interface statement at the [edit protocols l2circuit local-switching] hierarchy level. To configure an end interface, include the end-interface statement at the [edit protocols l2circuit local-switching interface interface-name] hierarchy level. To specify APS protect interfaces, include the protect-interface statement at the [edit protocols l2circuit local-switching interface interface-name] or [edit protocols l2circuit local-switching interface interface-name end-interface interface-name] hierarchy levels.

[edit]
protocols {
l2circuit {
local-switching {
interface interface1 {
protect-interface interface2;
end-interface interface3 {
protect-interface interface4;
}
}
interface interface5 {
protect-interface interface6;
end-interface interface7 {
protect-interface interface8;
}
}
}
}
}

Option: Configuring Layer 2 Circuits Simultaneously over RSVP and LDP LSPs

You can configure a Layer 2 circuit simultaneously over an RSVP LSP and an LDP LSP between the same two routing platforms. To accomplish this, do the following:

To verify that your configuration is operational, issue the show l2circuit connections command. This command has been enhanced to display tunnel endpoints. For more information about configuring Layer 2 circuits simultaneously over RSVP and LDP LSPs, see the JUNOS VPNs Configuration Guide.

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