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Configuring a Forwarding Table Filter

A forwarding table filter allows you to filter data packets based on their components and to perform an action on packets that match the filter.

To configure a forwarding table filter, do the following:

  1. Define a forwarding table filter:
    1. Configure the family address type: IPv4 (inet), IPv6 (inet6), Layer 2 traffic bridge, or MPLS (mpls).
    2. Define one or more terms, which are named structures in which match conditions and actions are defined.
    3. Define a match condition, which is the criterion against which a bearer packet is compared; for example, the IP address of a source device or a destination device. You can specify multiple criteria in a match condition.
    4. Define an action, which is what happens if all criteria match; for example, the gateway GPRS support node (GGSN) accepting the bearer packet, performing a lookup in the forwarding table, and forwarding the packet to its destination; discarding the packet; and discarding the packet and returning a rejection message. In addition to an action, you can define one or more action modifiers, which are actions that are taken in addition to the GGSN accepting or discarding a packet when all criteria match; for example, counting the packets and logging a packet.

    For more information about configuring firewall filters, see Configuring Firewall Filters.

  2. Apply the forwarding table filter as an input filter to a forwarding table. The forwarding table filter controls which bearer packets the router accepts and forwards.

For more information about configuring firewall filters, see Configuring Firewall Filters.

To define a forwarding table filter, include the firewall statement at the [edit] hierarchy level:

[edit]
firewall {
family family-name {
filter filter-name {
term term-name {
from {
match-conditions;
}
then {
action;
action-modifiers;
}
}
}
}
}

To create a forwarding table, include the instance-type statement at the [edit routing-instance instance-name] hierarchy level:

[edit]
routing-instance instance-name {
instance-type forwarding;
}

To apply a forwarding table filter to a VPN routing and forwarding (VRF) table, include the filter input statement at the [edit routing-instance instance-name forwarding-options family family-name] hierarchy level:

[edit]
routing-instance instance-name {
instance-type forwarding;
forwarding-options {
family family-name {
filter {
input filter-name;
}
}
}
}

To apply a forwarding table filter to a forwarding table, include the filter input statement at the [edit forwarding-options family family-name] hierarchy level:

[edit forwarding-options family family-name]
filter {
input filter-name;
}

To apply a forwarding table filter to the default forwarding table inet.0, which is not associated with a specific routing instance, include the filter input statement at the [edit forwarding-options family inet] hierarchy level:

[edit]
filter {
input filter-name;
}

For information about the routing-instance and routing-options statements, see the JUNOS Routing Protocols Configuration Guide.

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