D-Link DFL-260 Product Manual - Page 160

Policy-based Routing, 4.3.1. Overview

Page 160 highlights

4.3. Policy-based Routing Chapter 4. Routing 4.3. Policy-based Routing 4.3.1. Overview Policy-based Routing (PBR) is an extension to the standard routing described previously. It offers administrators significant flexibility in implementing routing decision policies by being able to define rules so alternative routing tables are used. Normal routing forwards packets according to destination IP address information derived from static routes or from a dynamic routing protocol. For example, using OSPF, the route chosen for packets will be the least-cost (shortest) path derived from an SPF calculation. Policy-based Routing means that routes chosen for traffic can be based on specific traffic parameters. Policy-based Routing can allow: Source based routing Service-based Routing User based Routing A different routing table may need to be chosen based on the source of traffic. When more than one ISP is used to provide Internet services, Policy-based Routing can route traffic originating from different sets of users through different routes. For example, traffic from one address range might be routed through one ISP, whilst traffic from another address range might be through a second ISP. A different routing table might need to be chosen based on the service. Policy-based Routing can route a given protocol such as HTTP, through proxies such as Web caches. Specific services might also be routed to a specific ISP so that one ISP handles all HTTP traffic. A different routing table might need to be chosen based on the user identity or the group to which the user belongs. This is particularly useful in provider-independent metropolitan area networks where all users share a common active backbone, but each can use different ISPs, subscribing to different providers. Policy-based Routing implementation in NetDefendOS is based on two building blocks: • One or more user-defined alternate Policy-based Routing Tables in addition to the standard default main routing table. • One or more Policy-based routing rules which determines which routing table to use for which traffic. 4.3.2. Policy-based Routing Tables NetDefendOS, as standard, has one default routing table called main. In addition to the main table, it is possible to define one or more, additional alternate routing tables (this section will sometimes refer to these Policy-based Routing Tables as alternate routing tables). Alternate routing tables contain the same information for describing routes as main, except that there is an extra parameter ordering defined for each of them. This parameter decides how route lookup is done using alternate tables in conjunction with the main table. This is described further in Section 4.3.5, "The Ordering parameter". 4.3.3. Policy-based Routing Rules A rule in the policy-based routing rule set can decide which routing table is selected. A Policy-based Routing rule can be triggered by the type of service (HTTP for example) in combination with the Source/Destination Interface and Source/Destination Network. 160

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4.3. Policy-based Routing
4.3.1. Overview
Policy-based Routing
(PBR) is an extension to the standard routing described previously. It offers
administrators significant flexibility in implementing routing decision policies by being able to
define rules so alternative routing tables are used.
Normal routing forwards packets according to destination IP address information derived from static
routes or from a dynamic routing protocol. For example, using OSPF, the route chosen for packets
will be the least-cost (shortest) path derived from an SPF calculation. Policy-based Routing means
that routes chosen for traffic can be based on specific traffic parameters.
Policy-based Routing can allow:
Source based routing
A different routing table may need to be chosen based on the
source of traffic. When more than one ISP is used to provide
Internet
services,
Policy-based
Routing
can
route
traffic
originating from different sets of users through different routes.
For example, traffic from one address range might be routed
through one ISP, whilst traffic from another address range might
be through a second ISP.
Service-based Routing
A different routing table might need to be chosen based on the
service. Policy-based Routing can route a given protocol such as
HTTP, through proxies such as Web caches. Specific services
might also be routed to a specific ISP so that one ISP handles all
HTTP traffic.
User based Routing
A different routing table might need to be chosen based on the
user identity or the
group
to which the user belongs. This is
particularly useful in
provider-independent metropolitan area
networks
where all users share a common active backbone, but
each can use different ISPs, subscribing to different providers.
Policy-based Routing implementation in NetDefendOS is based on two building blocks:
One or more user-defined alternate
Policy-based Routing Tables
in addition to the standard
default
main
routing table.
One or more
Policy-based routing rules
which determines which routing table to use for which
traffic.
4.3.2. Policy-based Routing Tables
NetDefendOS, as standard, has one default routing table called
main
. In addition to the
main
table,
it is possible to define one or more, additional alternate routing tables (this section will sometimes
refer to these Policy-based Routing Tables as
alternate
routing tables).
Alternate routing tables contain the same information for describing routes as
main
, except that
there is an extra parameter
ordering
defined for each of them. This parameter decides how route
lookup is done using alternate tables in conjunction with the
main
table. This is described further in
Section 4.3.5, “The Ordering parameter”
.
4.3.3. Policy-based Routing Rules
A rule in the policy-based routing rule set can decide which routing table is selected. A Policy-based
Routing rule can be triggered by the type of service (HTTP for example) in combination with the
Source/Destination Interface and Source/Destination Network.
4.3. Policy-based Routing
Chapter 4. Routing
160