Layer 2 Vpn Architectures [Electronic resources] نسخه متنی

Layer 2 Local Switching with Interworking

This section brings together the two previous sections of IW and local switching to provide another building block of the Cisco Unified VPN suite: any-to-any local switching. The configuration aspect also uses the two core commands of each of the previous sections: the connect command and the interworking keyword.

In this section, you learn the configuration and verification of the following case studies:

Case Study 14-11: Ethernet-to-VLAN Local Switching

Case Study 14-12: ATM Attachment Circuits and Local Switching

Case Study 14-11: Ethernet-to-VLAN Local Switching

This section discusses the mechanisms to implement local switching between Ethernet and Ethernet VLAN attachment circuits, using the topology shown in Figure 14-15.

The configuration that is required in the SanFran PE is shown in Example 14-43.

Example 14-43. Configuring Ethernet-to-VLAN Local Switching

!
hostname SanFran
!
interface Ethernet2/0
no ip address
!
interface Ethernet3/0
no ip address
!
interface Ethernet3/0.1
encapsulation dot1Q 27
!
connect eth-vlan Ethernet2/0 Ethernet3/0.1 interworking ethernet
!
!

You can see that this example uses the global command connect with diverse interfaces, and it prompts you for the IW type. The IW types are also IP or Ethernet.

You can perform connection verification from the SanFran PE and connectivity checking from the SanJose CE (see Example 14-44).

Example 14-44. Verifying Ethernet-to-VLAN Local Switching

SanFran#show connection name eth-vlan
Connection: 4 - eth-vlan
Current State: UP
 Segment 1: Ethernet2/0 up                                             
 Segment 2: Ethernet3/0.1 up                                           
 Interworking Type: ethernet                                           
SanFran#
SanJose#ping 192.168.52.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.52.1, timeout is 2 seconds:
!!!!!                                                                  
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/29/36 ms
SanJose#

The show connection command shows the IW type as Ethernet.

Case Study 14-12: ATM Attachment Circuits and Local Switching

This section deals with Layer 2 VPN local switching with IW and goes over some details and ideas that are helpful when using ATM PVC attachment circuits.

When you are configuring ATM-to-Ethernet Local Switching Interworking (LSIW) or ATM-to-Ethernet-VLAN LSIW, both IP and Ethernet types of IW are supported. With IP IW, you can configure the ATM PVC for either AAL5SNAP (in which translation takes place) or AAL5MUX (without translation because the AAL5 packet begins with raw IP). On the other hand, when you are using Ethernet IW, only AAL5SNAP PVC encapsulation is supported.

Creating the ATM PVC is not required. When you enter the connect command without the existing PVC, the PVC-A is created automatically and assigned AAL5SNAP encapsulation. If, however, you create the ATM PVC, you need to specify the l2transport keyword to indicate that it is a switched PVC and not a terminating PVC.

When you are configuring ATM-to-Frame Relay IW, only IP IW is supported. The ATM PVC encapsulation can either be AAL5SNAP or AAL5NLPID.

Table 14-3 summarizes the PVC encapsulation options while using ATM local switching with and without IW.

Segment 1 (Attachment Circuit)

Segment 2 (Attachment Circuit)

Interworking (IW) Type

ATM PVC Encapsulations