Table Of Contents
Configuring Layer 2 Local Switching
The Layer 2 Local Switching feature allows you to switch Layer 2 data between two physical or virtual interfaces of the same type on the same router. The interfaces can be on the same line card or on two different line cards. In local switching, the Layer 2 address is used, not a Layer 3 address.
Local switching can be used by incumbent local exchange carriers (ILECs) who use an interexchange carrier (IXC) to carry traffic between two local exchange carriers. Telecom regulations require the ILECs to pay the IXCs to carry that traffic. At times, the ILECs cannot terminate customer connections that are in different local access and transport areas (LATAs). In other cases, customer connections terminate in the same LATA, which may also be on the same router.
For example, Company A has more than 50 LATAs across the country and uses three routers for each LATA. Company A uses Companies B and C to carry traffic between local exchange carriers. Local switching of Layer 2 frames on the same router might be required.
The Layer 2 Local Switching feature is described in the following topics:
Feature History for Layer 2 Local Switching
Restrictions for Layer 2 Local Switching
The Layer 2 Local Switching feature is supported only between:
•PVCs on ATM interfaces in AAL5 SDU mode
•Frame Relay interfaces
Standards 1 Title
An Architecture for L2VPNs
1 Not all supported standards are listed.
The Cisco Frame Relay Management Information Base (MIB) adds extensions to the standard Frame Relay MIB (RFC 1315). It provides additional link-level and virtual circuit-level information and statistics that are mostly specific to Cisco Frame Relay implementation. This MIB provides Simple Network Management Protocol (SNMP) network management access to most of the information covered by the show frame-relay commands, such as show frame-relay lmi, show frame-relay pvc, show frame-relay map, and show frame-relay svc.
Configuring ATM-to-ATM PVC Local Switching
The following ATM line cards are supported for Cisco 10000 series routers:
To configure ATM-to-ATM PVC local switching, enter the following commands, beginning in global configuration mode:
Example 17-1 shows how to enable ATM AAL5 SDU mode Layer 2 local switching.
Example 17-1 Enabling ATM AAL5 SDU Mode Layer 2 Local Switchinginterface atm 1/0/0pvc 0/100 l2transportencapsulation aal5interface atm 2/0/0pvc 0/50 l2transportencapsulation aal5connect conn1 atm 1/0/0 0/100 atm 2/0/0 0/50
Configuring OAM Cell Emulation for Layer 2 Local Switching
If a provider edge (PE) router does not support the transport of Operation, Administration, and Maintenance (OAM) cells across a Link State Protocol (LSP) data unit, you can use OAM cell emulation to locally terminate or loop back the OAM cells. You configure OAM cell emulation on both PE routers, which emulates a VC by forming two unidirectional LSPs. You use the oam-ac emulation-enable and oam-pvc manage commands on both PE routers to enable OAM cell emulation.
After you enable OAM cell emulation on a router, you can configure and manage the ATM VC in the same manner as you would a terminated VC. A VC that has been configured with OAM cell emulation can send loopback cells at configured intervals toward the local customer edge (CE) router.
The endpoint can be either of the following:
•End-to-end loopback, which sends OAM cells to the local CE router.
•Segment loopback, which responds to OAM cells to a device along the path between the PE and CE routers.
The OAM cells include the following:
•Alarm indication signal (AIS)
•Remote defect indication (RDI)
These cells identify and report defects along a VC. When a physical link or interface failure occurs, intermediate nodes insert OAM AIS cells into all the downstream devices affected by the failure. When a router receives an AIS cell, it marks the ATM VC down and sends an RDI cell to let the remote end know about the failure.
Note For AAL5 over Multiprotocol Label Switching (MPLS), you can configure the oam-pvc manage command only after you issue the oam-ac emulation-enable command.
You can configure OAM cell emulation for ATM AAL5 SDU support over MPLS in the following ways:
Configuring OAM Cell Emulation for ATM AAL5 SDU Support over MPLS on PVCs
To configure OAM cell emulation for ATM AAL5 SDU support over MPLS on a PVC, enter the following commands, beginning in global configuration mode:
Example 17-2 shows how to enable OAM cell emulation on an ATM PVC.
Example 17-2 Enabling OAM Cell Emulation on an ATM PVCinterface ATM 1/0/0pvc 1/200 l2transportencapsulation aal5xconnect 126.96.36.199 100 encapsulation mplsoam-ac emulation-enableoam-pvc manage
Example 17-3 shows how to set the rate at which an AIS cell is sent to every 30 seconds.
Example 17-3 Setting the AIS Send Rate in OAM Cell Emulation on an ATM PVCinterface ATM 1/0/0pvc 1/200 l2transportencapsulation aal5xconnect 188.8.131.52 100 encapsulation mplsoam-ac emulation-enable 30oam-pvc manage
Verifying OAM Cell Emulation on an ATM PVC
In Example 17-4, the show atm pvc command shows that OAM cell emulation is enabled on the ATM PVC.
Example 17-4 OAM Cell Emulation Is EnabledRouter# show atm pvc 5/500ATM4/1/0.200: VCD: 6, VPI: 5, VCI: 500UBR, PeakRate: 1AAL5-LLC/SNAP, etype:0x0, Flags: 0x34000C20, VCmode: 0x0OAM Cell Emulation: enabled, F5 End2end AIS Xmit frequency: 1 second(s)OAM frequency: 0 second(s), OAM retry frequency: 1 second(s)OAM up retry count: 3, OAM down retry count: 5OAM Loopback status: OAM DisabledOAM VC state: Not ManagedVerifiedILMI VC state: Not ManagedInPkts: 564, OutPkts: 560, InBytes: 19792, OutBytes: 19680InPRoc: 0, OutPRoc: 0InFast: 4, OutFast: 0, InAS: 560, OutAS: 560InPktDrops: 0, OutPktDrops: 0CrcErrors: 0, SarTimeOuts: 0, OverSizedSDUs: 0Out CLP=1 Pkts: 0OAM cells received: 26F5 InEndloop: 0, F5 InSegloop: 0, F5 InAIS: 0, F5 InRDI: 26OAM cells sent: 77F5 OutEndloop: 0, F5 OutSegloop: 0, F5 OutAIS: 77, F5 OutRDI: 0OAM cell drops: 0Status: UP
Example 17-5 shows the output of the show connection command.
Example 17-5 Output of the show connection CommandRouter# show connectionID Name Segment 1 Segment 2 State==================================================================2 atm_conn_1 AT6/0/0.1 AAL5 1/100 AT6/0/1.1 AAL5 1/100 UP
Example 17-6 shows that the ATM PVCs are up.
Example 17-6 Output of the show atm pvc CommandRouter# show atm pvcVCD/ Peak Avg/Min BurstInterface Name VPI VCI Type Encaps SC Kbps Kbps Cells Sts6/0/0.1 4 1 100 PVC AAL5 UBR 149760 UP6/0/1.1 2 1 100 PVC AAL5 UBR 149760 UP
Configuring OAM Cell Emulation for ATM AAL5 SDU Support over MPLS in VC Class Configuration Mode
The following steps explain how to configure OAM cell emulation as part of a VC class. You can then apply the VC class to an interface, a subinterface, or a VC. When you configure OAM cell emulation in VC class configuration mode and then apply the VC class to an interface, the settings in the VC class apply to all the VCs on the interface; unless you specify a different OAM cell emulation value at a lower level, such as the subinterface or VC level.
For example, you can create a VC class that specifies OAM cell emulation and sets the rate of AIS cells to every 30 seconds. You can apply the VC class to an interface. Then, for one PVC, you can enable OAM cell emulation and set the rate of AIS cells to every 15 seconds. All the PVCs on the interface use the cell rate of 30 seconds, except for the one PVC that was set to 15 seconds.
To enable OAM cell emulation as part of a VC class and apply it to an interface, enter the following commands, beginning in global configuration mode:
Example 17-7 configures OAM cell emulation for ATM AAL5 SDU support over MPLS in VC class configuration mode. The VC class is then applied to an interface.
Example 17-7 Enabling OAM Cell Emulation for ATM AAL5 SDU Support over MPLS in VC Class Configuration Mode—VC Class Applied to an Interface with an AIS Rate of 30vc-class atm oamclassencapsulation aal5oam-ac emulation-enable 30oam-pvc manageinterface atm1/0class-int oamclasspvc 1/200 l2transportxconnect 184.108.40.206 100 encapsulation mpls
Example 17-8 configures OAM cell emulation for ATM AAL5 over MPLS in VC class configuration mode. The VC class is then applied to a PVC.
Example 17-8 Enabling OAM Cell Emulation for ATM AAL5 SDU Support over MPLS in VC Class Configuration Mode—VC Class Applied to a PVCvc-class atm oamclassencapsulation aal5oam-ac emulation-enable 30oam-pvc manageinterface atm1/0pvc 1/200 l2transportclass-vc oamclassxconnect 220.127.116.11 100 encapsulation mpls
Example 17-9 configures OAM cell emulation for ATM AAL5 over MPLS in VC class configuration mode. The VC class is then applied to an interface. One PVC is configured with OAM cell emulation at an AIS rate of 10. That PVC uses the AIS rate of 10 instead of 30.
Example 17-9 Enabling OAM Cell Emulation for ATM AAL5 SDU Support over MPLS in VC Class Configuration Mode—VC Class Applied to an Interface with an AIS Rate of 10vc-class atm oamclassencapsulation aal5oam-ac emulation-enable 30oam-pvc manageinterface atm1/0class-int oamclasspvc 1/200 l2transportoam-ac emulation-enable 10xconnect 18.104.22.168 100 encapsulation mpls
Configuring Frame Relay-to-Frame Relay Local Switching
Frame Relay switching is a means of switching packets based upon the data link connection identifier (DLCI), which can be looked upon as the Frame Relay equivalent of a MAC address. You perform the switching by configuring your router or access server as a Frame Relay network. There are two parts to a Frame Relay network: the Frame Relay data terminal equipment (DTE) (the router or access server) and the Frame Relay data communications equipment (DCE) switch.
Local switching allows you to switch Layer 2 data between two interfaces of the same type for example, ATM-to-ATM, or Frame-Relay-to-Frame-Relay.
For background information about Frame-Relay-to-Frame-Relay Local Switching, see the Distributed Frame Relay Switching feature guide.
You can switch between virtual circuits on the same port, as detailed in the "Configuring Frame Relay Same-Port Switching" section.
The following channelized line cards are supported for the Cisco 10000 series routers:
•1-Port Channelized OC-12/STM-4
•4-Port Channelized OC-3/STM-1
•6-Port Channelized T3
•24-Port Channelized E1/T1
The following packet over SONET line cards are supported for the Cisco 10000 series routers:
•1-Port OC-12 Packet over SONET
•1-Port OC-48/STM-16 Packet over SONET
•6-Port OC-3/STM-1 Packet over SONET
The Frame Relay-to-Frame Relay Local Switching feature is described in the following topics:
Configuring Frame Relay for Local Switching
To configure Frame Relay for local switching, enter the following commands, beginning in global configuration mode.
Example 17-10 configures Frame-Relay-to-Frame-Relay for local switching.
Example 17-10 Configuring Frame Relay-to-Frame Relay for Local Switchingframe-relay switchinginterface serial 1/0/0.1/1:0
frame-relay interface-dlci 100 switched
exitconnect connection1 serial1/0/0.1/1:0 100 serial2/0/0.1/2:0 101
Configuring Frame Relay Same-Port Switching
Use the following steps to configure local Frame Relay same-port switching on a single interface, beginning in global configuration mode.
Example 17-11 configures Frame Relay same-port switching.
Example 17-11 Configuring Frame Relay Same-Port Switchingframe-relay switchinginterface serial 1/0/0.1/1:0encapsulation frame-relayframe-relay intf-type nniframe-relay interface-dlci 100 switchedexitexitconnect connection1 serial1/0 100 serial1/0 200
Verifying Layer 2 Local Switching for Frame Relay
To verify configuration of the Layer 2 Local Switching feature, use the show connection frame-relay-to-frame-relay command and the show frame-relay pvc command in privileged EXEC mode.
Example 17-12 shows the output of the show connection frame-relay-to-frame-relay command, which displays the local connection between a Frame Relay interface and a Frame Relay local switching interface.
Example 17-12 Output of the show connection frame-relay-to-frame-relay CommandRouter# show connection frame-relay-to-frame-relayID Name Segment 1 Segment 2 State==================================================================1 fr2fr Se3/0/0.1/1:0 100 Se3/0/0.1/2:0 200 UP
Example 17-13 shows the output of the show frame-relay pvc command, which shows a switched Frame Relay PVC.
Example 17-13 Output of the show frame-relay pvc CommandRouter# show frame-relay pvc 16PVC Statistics for interface POS5/0 (Frame Relay NNI)DLCI = 16, DLCI USAGE = SWITCHED, PVC STATUS = UP, INTERFACE = POS5/0LOCAL PVC STATUS = UP, NNI PVC STATUS = ACTIVEinput pkts 0 output pkts 0 in bytes 0out bytes 0 dropped pkts 100 in FECN pkts 0in BECN pkts 0 out FECN pkts 0 out BECN pkts 0in DE pkts 0 out DE pkts 0out bcast pkts 0 out bcast bytes 0switched pkts 0Detailed packet drop counters:no out intf 0 out intf down 100 no out PVC 0in PVC down 0 out PVC down 0 pkt too big 0pvc create time 00:25:32, last time pvc status changed 00:06:31
Configuring QoS Features
For information about configuring QoS features on the Cisco 10000 series router, see the Cisco 10000 Series Router Quality of Service Configuration Guide.
The values shown in the tables are as follows:
•No—You cannot perform this policy map action
•Yes—You can perform this policy map action
•N/A (not applicable)—You can apply the policy map action but it will not have any effect on packets
Monitoring and Maintaining Layer 2 Local Switching
To monitor and maintain the configuration of the Layer 2 Local Switching feature, use the following commands in privileged EXEC mode.
Caution Because debugging output is assigned high priority in the CPU process, it can render the system unusable. For this reason, use debug commands only to troubleshoot specific problems or during troubleshooting sessions with Cisco Systems technical support personnel. It is best to use debug commands during periods of lower network traffic and fewer users. Debugging during these periods decreases the likelihood that increased debug command processing overhead will affect system use.