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264 Extreme Networks Consolidated Hardware Guide

BlackDiamond 6800 Series I/O Modules

By mapping to a specific FEC, the MPLS label efficiently provides the router with all of the local link

information needed for immediate forwarding to the next hop. MPLS creates a Label Switched Path

(LSP) along which each Label Switch Router (LSR) can make forwarding decisions based solely upon

the content of the labels. At each hop, the LSR simply strips off the existing label and applies a new

one that tells the next LSR how to forward the packet.

MPLS Layer-2 VPNs. As networks grow and become more pervasive, the need to separate the

physical network infrastructure from the logical network or VLAN organization has become

increasingly important. By logically separating the network topology from the service provided by the

physical network, services are more easily managed, reliability through increased redundancy is

improved, and you gain more efficient use of the physical network infrastructure.

By mapping a VLAN to a specific set of MPLS tunnels, you can create virtual private networks (VPNs).

Within a VPN, all traffic is opaquely transported across the service provider network. Each VPN can be

managed and provisioned independently.

VPNs may have two or more customer points of presence (PoP). All PoPs are interconnected using

point-to-point tunnels. If there are two PoPs in the VPN, the VPN is considered to be point-to-point. If

there are more than two PoPs in the VPN, the VPN is considered to be multipoint. Multipoint VPNs can

be fully-meshed or hub-and-spoke.

Layer-2 VPNs are constructed from a set of interconnected point-to-point MPLS tunnels. Tunnel

endpoint nodes operate as virtual VPN switches, bridging traffic between tunnels and the local egress

VLAN. MAC caching is integrated into the MPLS module. Source MAC addresses within each VPN are

associated with the tunnel from which the packet is received. Up to 256K MAC addresses can be

cached. Within a VPN, once a MAC address has been learned, unicast traffic destined to the cached

MAC address is transmitted over a single tunnel. Integrated VPN MAC caching enhancement increases

network performance and improves VPN scalability.

IP Unicast Forwarding. IP unicast packets are forwarded in the MPLS module using the longest prefix

match algorithm. IP unicast forwarding is required to switch packets at ingress or upon egressing an

MPLS network domain.

All IP unicast forwarding is performed on the MPLS module to facilitate implementation of MPLS and

accounting. When MPLS, longest prefix match, or accounting functions are enabled, the MPLS module,

rather than the switch fabric hardware, performs layer-3 IP unicast forwarding. Layer-2 switching and

Layer-3 IP multicast forwarding are unaffected. See the ExtremeWare Software User Guide for more

information about configuring longest prefix match on the MPLS module.

ExtremeWare distributes its IP unicast routing table, ARP table, MPLS incoming label mappings (ILMs),

FEC-to-NHFLE database, and interface IP addresses to each MPLS module so that every MPLS module

contains the same IP routing database.

Each MPLS module has sufficient capacity to support 256K IP longest prefix match lookup route entries.

Each route entry also supports up to four equal-cost paths. IP forwarding is configurable per VLAN.

Each MPLS module IP routing database provides an aggregate IP forwarding throughput of up to 4

Gbps. The total forwarding throughput for a single BlackDiamond chassis can be scaled up to 16 Gbps

by adding up to four MPLS modules. MPLS modules interface to the BlackDiamond switch fabric via

four 1 Gbps internal links. IP unicast traffic is internally forwarded from the BlackDiamond I/O

modules using one of three backplane load-sharing policies: port-based, address-based, or round-robin.

See the ExtremeWare Software User Guide for more information.

Destination-Sensitive Accounting. Counts of IP packets and bytes are maintained based on the IP

routes used to forward packets. Destination-sensitive accounting gives you the flexibility to bill your

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