A number of parameters determine the behavior of a packet after it has been matched to a defined criterion or set of criteria:
the action configured by the user
the context in which a filter policy is applied. For example, applying a filter policy in an unsupported context can result in simply forwarding the packet instead of applying the configured action.
external factors, such as the reachability (according to specific test criteria) of a target
Because of this, SR OS provides the following commands that enable the user to capture this context globally and identify how a packet is handled by the system:
show>filter>ip
show>filter>ipv6
show>filter>mac
This section describes the key information displayed as part of the output for the show commands listed above, and how to interpret it.
From a configuration point of view, the show command output displays the main action (primary and secondary), as well as the extended action.
The ‟PBR Target Status” field shows the basic information that the system has of the target based on simple verification methods. This information is only shown for the filter entries which are configured in redundancy mode (that is, with both primary and secondary main actions configured), and for ESI redirections. Specifically, the target status in the case of redundancy depends on several factors; for example, on a match in the routing table for next-hop redirects, or on VXLAN tunnel resolution for ESI redirects.
The ‟Downloaded Action” field specifically describes the action that the system performs on the packets that match the criterion (or criteria). This typically depends on the context in which the filter has been applied (whether it is supported or not), but in the case of redundancy, it also depends on the target status. For example, the downloaded action is the secondary main action when the target associated with the primary action is down. In the nominal (for example, non-failure condition) case the ‟Downloaded Action” reflects the behavior a packet is subject to. However, in transient cases (for example, in the case of a failure) it may not be able to capture what effectively happens to the packet.
The output also displays relevant information such as the default action when the target is down (see Table: Default behavior when a PBR/PBF target is down) as well as the overridden default action when pbr-down-action-override has been configured.
There are situations where, collectively, this information does not capture what effectively happens to the packet throughout the system. The effective-action keyword of the show>filter>[{ip | ipv6 | mac}] commands enables advanced checks to be performed and accurate packet fates to be displayed.
The criteria for determining when a target is down. While there is little ambiguity on that aspect when the target is local to the system performing the steering action, ambiguity is much more prominent when the target is distant. Therefore, because the use of effective-action triggers advanced tests, a discrepancy is introduced compared to the action when effective-action keyword is not used. This is, for example, be the case for redundant actions.