Policy-based routing
Encyclopedia
In computer networking, policy-based routing (PBR) is a technique used to make routing
decisions based on policies set by the network administrator.
When a router receives a packet it normally decides where to forward it based on the destination address in the packet, which is then used to look up an entry in a routing table
. However, in some cases, there may be a need to forward the packet based on other criteria. For example, a network administrator might want to forward a packet based on the source address, not the destination address. This should not be confused with source routing
.
Policy-based routing may also be based on the size of the packet, the protocol of the payload, or other information available in a packet header or payload. This permits routing of packets originating from different sources to different networks even when the destinations are the same and can be useful when interconnecting several private networks.
In the Cisco IOS
, PBR is implemented using route maps..
Linux supports multiple routing tables since version 2.2.
FreeBSD supports PBR using either IPFW
or OpenBSD's PF
.
Routing
Routing is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...
decisions based on policies set by the network administrator.
When a router receives a packet it normally decides where to forward it based on the destination address in the packet, which is then used to look up an entry in a routing table
Routing table
In computer networking a routing table, or Routing Information Base , is a data table stored in a router or a networked computer that lists the routes to particular network destinations, and in some cases, metrics associated with those routes. The routing table contains information about the...
. However, in some cases, there may be a need to forward the packet based on other criteria. For example, a network administrator might want to forward a packet based on the source address, not the destination address. This should not be confused with source routing
Source routing
In computer networking, source routing allows a sender of a packet to partially or completely specify the route the packet takes through the network...
.
Policy-based routing may also be based on the size of the packet, the protocol of the payload, or other information available in a packet header or payload. This permits routing of packets originating from different sources to different networks even when the destinations are the same and can be useful when interconnecting several private networks.
In the Cisco IOS
Cisco IOS
Cisco IOS is the software used on the vast majority of Cisco Systems routers and current Cisco network switches...
, PBR is implemented using route maps..
Linux supports multiple routing tables since version 2.2.
FreeBSD supports PBR using either IPFW
Ipfirewall
ipfirewall or ipfw is a FreeBSD IP packet filter and traffic accounting facility. Its ruleset logic is similar to many other packet filters except IPFilter. ipfw is authored and maintained by FreeBSD volunteer staff members. Its syntax enables use of sophisticated filtering capabilities and thus...
or OpenBSD's PF
PF (firewall)
PF is a BSD licensed stateful packet filter, a central piece of software for firewalling. It is comparable to iptables, ipfw and ipfilter...
.