The Basic AToM Configuration

The basic configuration for AToM is pretty straightforward. You must first select the encapsulation type of the customer-facing (CE-facing) interface on the PE with the following command:

Router(config-if)# encapsulation encapsulation-type

Then you enable AToM by specifying the xconnect command on the CE-facing interface, as follows:

Router(config-if)# xconnect peer-router-id vcid encapsulation mpls

The peer-router-id is the LDP router ID of the remote PE router. The vcid is the identifier that you assign to the pseudowire. The VCID has to be unique per pair of PE routers. As soon as you configure this command on the interface—on both PE routers—the targeted LDP session is established between the two PE routers. The specification of the MPLS encapsulation is optional, because you can also specify it in the pseudowire class. The pseudowire class is not required on the PE router to configure AToM, but it is necessary if you need to specify more than just the encapsulation to be MPLS. In the pseudowire class, you can specify certain characteristics of the pseudowires. Interworking, preferred-path, and sequencing are such configurable characteristics, besides the encapsulation type. The only other encapsulation type available besides MPLS is L2TPv3. Interworking, preferred-path, and sequencing are explained in following sections of this chapter.

Figure 10-9 shows a basic example of an AToM network with two PE routers that provide an AToM service to the two CE routers, CE1 and CE2. The transported Layer 2 protocol is HDLC.

Figure 10-9 AToM Example for HDLC

Targeted LDP Session

Figure 10-9 AToM Example for HDLC

Targeted LDP Session

Serial 0/1/0

Attachment Circuit (AC)

Attachment Circuit (AC)

Serial 0/1/0

Attachment Circuit (AC)

Attachment Circuit (AC)

You can see the basic configuration needed on the PE routers for AToM in Example 10-3.

Example 10-3 Basic AToM Configuration of PE1 and PE2

mpls ldp router-id Loopback0 force mpls label protocol ldp pseudowire-class one encapsulation mpls

interface Serial0/1/0 no ip address encapsulation hdlc xconnect 10.200.254.4 100 pw-class one

PE2#

mpls ldp router-id Loopback0 force mpls label protocol ldp pseudowire-class one encapsulation mpls

interface Serial4/0/0 no ip address encapsulation hdlc xconnect 10.200.254.1 100 pw-class one

NOTE The default encapsulation for a serial interface in Cisco IOS is HDLC, so it is normally not displayed in the configuration. It is shown here for clarity.

Example 10-4 shows that you can verify the state of the pseudowire with the show mpls l2transport command.

Example 10-4 Verifying AToM on PE1 and PE2 PE1#show mpls l2transport vc 100

Local intf Local circuit Dest address VC ID Status

Se0/1/0 HDLC 10.200.254.4 100 UP

PE1#show mpls l2transport vc 100 detail

Local interface: Se0/1/0 up, line protocol up, HDLC up

Example 10-4 Verifying AToM on PE1 and PE2 (Continued)

Destination address: 10.200.254.4, VC ID: 100, VC status: up Output interface: Et0/0/0, imposed label stack {19 23} Preferred path: not configured Default path: active

Tunnel label: 23, next hop 10.200.200.2 Create time: 01:11:35, last status change time: 00:03:31 Signaling protocol: LDP, peer 10.200.254.4:0 up MPLS VC labels: local 24, remote 19 Group ID: local 0, remote 0 MTU: local 1500, remote 1500 Remote interface description: Sequencing: receive disabled, send disabled VC statistics:

packet totals: receive 54, send 44 byte totals: receive 4964, send 4483 packet drops: receive 0, send 0

PE2#show mpls l2transport vc 100

Local intf Local circuit Dest address VC ID Status

Se4/0/0 HDLC 10.200.254.1 100 UP

PE2#show mpls l2transport vc 100 detail

Local interface: Se4/0/0 up, line protocol up, HDLC up

Destination address: 10.200.254.1, VC ID: 100, VC status: up Preferred path: not configured Default path: active

Tunnel label: 22, next hop point2point Output interface: Se5/0, imposed label stack {22 24} Create time: 00:12:23, last status change time: 00:03:51 Signaling protocol: LDP, peer 10.200.254.1:0 up MPLS VC labels: local 19, remote 24 Group ID: local 0, remote 0 MTU: local 1500, remote 1500 Remote interface description: Sequencing: receive disabled, send disabled Sequence number: receive 0, send 0 VC statistics:

packet totals: receive 50, send 64 byte totals: receive 4578, send 6984 packet drops: receive 0, seq error 0, send 0

PE1#show mpls l2transport binding 100

Destination Address: 10.200.254.4, VC ID: 100 Local Label: 24

Example 10-4 Verifying AToM on PE1 and PE2 (Continued)

Cbit: 1, VC Type: HDLC, GroupID: 0 MTU: 1500, Interface Desc: n/a VCCV Capabilities: Type 1, Type 2 Remote Label: 19

Cbit: 1, VC Type: HDLC, GroupID: 0 MTU: 1500, Interface Desc: n/a VCCV Capabilities: Type 1, Type 2

To see which AToM features the interface supports for each encapsulation type, use the show mpls l2transport hw-capability command, as shown in Example 10-5.

Example 10-5 Verifying AToM Features

PE1#show mpls l2transport hw-capability interface serial 0/1/0

Interface Serial0/1/0

Transport type FR DLCI Core functionality:

MPLS label disposition supported Distributed processing supported Control word processing supported Sequence number processing not supported VCCV Type 1 processing supported Edge functionality:

MPLS label imposition supported Distributed processing supported Control word processing supported Sequence number processing not supported

Transport type ATM AAL5 Core functionality:

MPLS label disposition supported Control word processing supported Sequence number processing not supported VCCV Type 1 processing supported Edge functionality: Not supported

Transport type ATM CELL Core functionality:

MPLS label disposition supported Control word processing not supported Sequence number processing not supported VCCV Type 1 processing not supported Edge functionality: Not supported

Example 10-5 Verifying AToM Features (Continued)

Transport type Eth VLAN Core functionality:

MPLS label disposition supported Distributed processing supported Control word processing supported Sequence number processing not supported VCCV Type 1 processing supported Edge functionality: Not supported

Transport type Ethernet Core functionality:

MPLS label disposition supported Distributed processing supported Control word processing supported Sequence number processing not supported VCCV Type 1 processing supported Edge functionality: Not supported

!output omitted for brevity

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