01-05 VPLS Troubleshooting

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VRP Troubleshooting - VPN

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Contents5 VPLS Troubleshooting..............................................................................................................5-15.1 VPLS Overview ............................................................................................................................................5-2 5.1.1 Related Concepts of VPLS...................................................................................................................5-2 5.1.2 Encapsulation Type ..............................................................................................................................5-3 5.1.3 MTU.....................................................................................................................................................5-4 5.2 VPLS Troubleshooting..................................................................................................................................5-4 5.2.1 Typical Networking..............................................................................................................................5-4 5.2.2 Configuration Notes.............................................................................................................................5-6 5.2.3 Troubleshooting Flowchart ..................................................................................................................5-9 5.2.4 Troubleshooting Procedures.................................................................................................................5-9 5.3 Troubleshooting Cases ................................................................................................................................5-10 5.3.1 A VSI Cannot Be Up in LDP Signaling Mode ...................................................................................5-11 5.3.2 Packets Cannot Be Forwarded Successfully Between Two PEs Though VSI Is Up..........................5-13 5.3.3 A VSI Cannot Be Up in BGP Signaling Mode...................................................................................5-14 5.4 FAQs ...........................................................................................................................................................5-16 5.5 Diagnostic Tools..........................................................................................................................................5-19 5.5.1 display Commands.............................................................................................................................5-19 5.5.2 debugging Command .........................................................................................................................5-19

Issue 01 (2009-06-01)

Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd.

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5 VPLS Troubleshooting

VRP Troubleshooting - VPN

FiguresFigure 5-1 Basic VPLS networking....................................................................................................................5-4 Figure 5-2 Hierarchical VPLS Networking........................................................................................................5-5 Figure 5-3 VPLS troubleshooting flowchart ......................................................................................................5-9 Figure 5-4 VPLS networking diagram .............................................................................................................5-11

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Huawei Proprietary and Confidential Copyright Huawei Technologies Co., Ltd.

Issue 01 (2009-06-01)

VRP Troubleshooting - VPN

5 VPLS Troubleshooting

5About This ChapterSection 5.1 VPLS Overview 5.2 VPLS Troubleshooting

VPLS Troubleshooting

The following table shows the contents of this chapter. Describes This section describes the knowledge you need to know before troubleshooting VPLS. This section describes the notes about configuring VPLS, and provides the VPLS troubleshooting flowchart and the troubleshooting procedure in a typical VPLS Network. This section presents several troubleshooting cases. This section lists frequently asked questions and their answers. This section describes common diagnostic tools: display commands and debugging commands.

5.3 Troubleshooting Cases 5.4 FAQs 5.5 Diagnostic Tools

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5 VPLS Troubleshooting

VRP Troubleshooting - VPN

5.1 VPLS OverviewThis section covers the following topics: Related Concepts of VPLS Encapsulation Type MTU The development of Ethernet has made it a dominant LAN technology and is increasingly applied as an access solution in the Metropolitan Area Network (MAN) and in the Wide Area Network (WAN). VPLS is used to connect more than one Ethernet LAN segments through the Packet Switched Network (PSN), to enable them to operate as if in a LAN. VPLS is also called Transparent LAN Service (TLS) or Virtual Private Switched Network service (VPSN). Unlike the common L2VPN point-to-point service, VPLS allows service providers to offer Ethernet-based multi-point service over the MPLS backbone network.

5.1.1 Related Concepts of VPLSPWA Pseudo Wire (PW) is a virtual connection used to transmit frames between two PEs. In the VPLS packet, PW corresponds to the inner label. The PE sets up and maintains a PW, at both ends. The setup of a PW is a process of generating local and remote labels by using signaling. Currently, LDP signaling and BGP signaling are supported. The following conditions should be met to enable a PW to be Up: At least one AC is Up at the local end. At least one VSI is Up at the remote end, and the negotiation parameters are consistent at both ends of the PW.

TunnelA tunnel is a direct virtual path, used to transparently transmit data. The tunnel in VPLS is used to carry PWs. Multiple PWs can be delivered on a single tunnel. To set up a PW to the remote, a tunnel to the remote end must be available first. The tunnel is set up by the tunnel management module. VPLS queries the tunnel against the tunnel management module according to the remote destination address of a PW. If there is no tunnel to the remote destination address, the PW cannot be set up. VPLS supports using the tunnel policy to choose a tunnel.

ACCE connects PE through the Attachment Circuit (AC) in an L2VPN.

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5 VPLS Troubleshooting

An AC can be either a physical link or a logical link. AC transfers frames between CE and PE. Users can specify a remote PE as the AC side of the local VPLS (upe often used). Then, the specified PE then need not fully connect with other PEs or perform split horizon. Similar to that in the distance vector (DV) routing protocol, the split horizon in VPLS can reduce the bandwidth consumption and prevent the loop.

VSIVirtual Switch Instance (VSI) implements the bridging function. In VPLS, a VSI on PE represents a VPN. A PE may have multiple VPNs. Therefore, a PE may be configured with multiple VSIs. Each VSI provides separate VPLS service.

5.1.2 Encapsulation TypePacket Encapsulation on the ACPacket encapsulation on the AC is determined by the user access mode. There are two user access modes. VLAN access: In this mode, the Ethernet frame sent upstream from CE or sent downstream from PE contains a VLAN tag in the frame header. This tag is a service delimiter used by the Internet Service Provider (ISP) to differentiate users. This type of tag is called P-tag. Ethernet access: In this mode, the Ethernet frame sent upstream by CE or sent downstream by PE does not contain P-tag. If the frame contains a VLAN tag in its header, this tag is an internal VLAN tag and is of no significance for PE. This type of internal VLAN tag is called U-tag. You can specify the access mode of the user on the device. Packet Encapsulation on the PW There are two types of packet encapsulation on the PW. Raw mode: In this mode, the P-tag is not transmitted over the PW. If the upstream packets on CE contain the service delimiter, their service delimiter is removed before they are sent upstream; two layers of MPLS labels are added to them before they are forwarded. If the upstream packets on CE do not contain service delimiter, they are sent upstream directly; two layers of MPLS labels are added to them before they are forwarded. For downstream packets on PE, the service delimiter is added to them as needed before they are forwarded to CE. It is not allowed to rewrite or remove an existent tag. Tagged mode: In this mode the frame sent to the PW must contain a P-tag. If the upstream packets on CE contain the service delimiter, they are sent upstream directly without the P-tag removed; two layers of MPLS labels are added to them before they are forwarded. If the upstream packets on CE do not contain the service delimiter, they are added a null tag and then sent upstream; two layers of MPLS labels are added to them before they are forwarded. For downstream packets on PE, their service delimiter is rewritten, removed or retained as needed before they are forwarded to CE.

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5.1.3 MTUIn VPLS, the MTU refers to the maximum transmission unit of the link layer. The encapsulation type and the MTU are both regarded as the Layer 2 information and are processed. The MTU of respective VPLS must be consistent in a same VPN. If inconsistency occurs, the PW cannot be set up successfully.