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Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 1 Broadband Aggregation and Leased-Line Overview
Load Balancing Architecture Models
Combined Broadband and Leased-Line Applications
The demarcation between leased-line and broadband applications has become less clear over the past few
years. DSL circuits are competing in the traditional leased-line space, with many service providers
offering Internet and VPN services over these lower-cost alternatives to dedicated TDM. The role of the
leased-line aggregator has expanded to include the termination of many traditional broadband interfaces
and encapsulations. Combining leased-line and business-class DSL access is one option that many
providers are introducing to reduce costs and consolidate the number of edge products.
Figure 1-16 shows an example of combined broadband and leased-line architecture.
Figure 1-16 Combined Broadband and Leased-Line Architecture
Load Balancing Architecture Models
This section describes how the Cisco 10000 series router load balances traffic in various network
topologies. The scenarios apply to a Cisco 10000 series router with a PRE2.
IP and MPLS Applications
Figure 1-17 shows a simple network topology that uses IP or basic MPLS forwarding. It does not include
MPLS VPN routes. There are multiple outgoing paths from the R1 router to the R2 router. Load
balancing is achieved by populating multiple paths in the PXF. On a Cisco 10000 series router, load
balancing is supported on a maximum of eight unique paths.
Figure 1-17 IP and MPLS Load Balancing
You can set load balancing to work per-destination or per-packet. For per-destination load balancing, the
packet arrives at R1 and the hash value is computed based on the source IP address, destination IP
address, and router ID. The PXF has a proprietary algorithm to select a path based on the number of total
paths available.
Cisco 10000
series
119489
VPN
Internet
access
Broadband
protocols
Ethernet
Lease- line
protocols
P1
P2
R1
R2
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