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Routing and Firewall Filter Policy Terms

Before configuring routing policies or firewall filters on a Services Router, you must become familiar with the terms defined in Table 54.

Table 54: Routing and Firewall Filter Policy Terms

firewall filter

See stateful firewall filter; stateless firewall filter.

multifield (MF) classifier

Firewall filter that scans through a variety of packet fields to determine the forwarding class and loss priority for a packet and polices traffic to a specific bandwidth and burst size. Typically, a classifier performs matching operations on the selected fields against a configured value.

network address port translation (NAPT)

Method of concealing a set of host ports on a private network behind a pool of public addresses. It can be used as a security measure to protect the host ports from direct targeting in network attacks.

Network Address Translation (NAT)

Method of concealing a set of host addresses on a private network behind a pool of public addresses. It can be used as a security measure to protect the host addresses from direct targeting in network attacks.

policer

Feature that limits the amount of traffic passing into or out of an interface. It is an essential component of firewall filters that is designed to thwart denial-of-service (DoS) attacks. A policer applies rate limits on bandwidth and burst size for traffic on a particular Services Router interface.

service set

Collection of services. Examples of services include stateful firewall filters and Network Address Translation (NAT).

stateful firewall filter

Type of firewall filter that evaluates the context of connections, permits or denies traffic based on the context, and updates this information dynamically. Context includes IP source and destination addresses, TCP port numbers, TCP sequencing information, and TCP connection flags.

stateless firewall filter

Type of firewall filter that statically evaluates the contents of packets transiting the router, and packets originating from, or destined for, the router. Information about connection states is not maintained.

term

Firewall filters contain one or more terms that specify filter match conditions and actions.

trusted network

Network from which all originating traffic can be trusted—for example, an internal enterprise LAN. Stateful firewall filters allow traffic to flow from trusted to untrusted networks.

untrusted network

Network from which all originating traffic cannot be trusted—for example, a WAN. Unless configured otherwise, stateful firewall filters do not allow traffic to flow from untrusted to trusted networks.


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