The Cisco PE switch must be configured to enforce the split-horizon rule for all pseudowires within a Virtual Private LAN Services (VPLS) bridge domain.

Description

<VulnDiscussion>A virtual forwarding instance (VFI) must be created on each participating PE switch for each customer VLAN using VPLS for carrier Ethernet services. The VFI specifies the VPN ID of a VPLS domain, the addresses of other PE switches in the domain, and the type of tunnel signaling and encapsulation mechanism for each peer PE switch. The set of VFIs formed by the interconnection of the emulated VCs is called a VPLS instance, which forms the logic bridge over the MPLS core network. The PE switches use the VFI with a unique VPN ID to establish a full mesh of emulated virtual circuits or pseudowires to all the other PE switches in the VPLS instance. The full-mesh configuration allows the PE switch to maintain a single broadcast domain. With a full-mesh configuration, signaling and packet replication requirements for each provisioned virtual circuit on a PE can be high. To avoid the problem of a packet looping in the provider core, thereby adding more overhead, the PE devices must enforce a split-horizon principle for the emulated virtual circuits; that is, if a packet is received on an emulated virtual circuit, it is not forwarded on any other virtual circuit.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>