Routers designed for high availability (HA) include hardware redundancy such as dual power supplies (PSU) and router processors (RP).
The RP is responsible for for learning the network topology and building the route table (RIB).
If the RP fails it can trigger routing protocol adjacencies to reset resulting in network instability.
During a RP failure it may be more desirable to hide the failure from the rest of the network and allow the router to continue forwarding packets using the previously programmed CEF table entries rather than drop packets and wait for the secondary router processor to rebuilt the forwarding table and re-establish adjacencies.
Stateful Switchover (SSO) is a redundancy feature that allows a Cisco device with two route processors to synchronise router configuration and control plane state information.
The processing of mirroring this information between route processors is known as checkpointing. Stateful Switchover enabled routers will always checkpoint line card operation and Layer 2 protocol states.
In a triggered failure event the standby route processor will immediately take control and prevent basic problems such as line interface flapping. Layer 3 forwarding is disrupted without additional configuration as the switchover will trigger a routing protocol adjacency flap that clears the route table.
When the route table is cleared, CEF entries will be purged and traffic no longer routed until the topology is relearned by the new route processor.
Enabling additional configuration in the form of nonstop forwarding (NSF) or nonstop routing (NSR) will keep CEF entries for a short duration in a failover event to keep packet forwarding in an event of an RP failure until the control plane has time to recover.
FAQs
Stateful Switchover (SSO) works with an active/standby redundancy system. Here, there are two route processors on the device. One is Active and the other is Standy. Standby processor is synchronized with the Active processor before any failure.
What are stateful switchover examtopics? ›
Stateful switchover (SSO) is a mechanism used to take control from a failed Route Processor (RP) while maintaining connectivity in a networking device, such as a router or switch.
What is Cisco Stateful Switchover? ›
Stateful Switchover (SSO) is a redundancy feature that allows a Cisco device with two route processors to synchronise router configuration and control plane state information. The processing of mirroring this information between route processors is known as checkpointing.
What is RP switchover? ›
Automatic and Manual RP Switchovers
An automatic switchover occurs when a fault causes the active RP to crash or reboot and if the active RP is not responding or is dead. A CLI command can be used to force a manual switchover between the active RP and the standby RP.
What is the difference between stateless and stateful switches? ›
A stateless system sends a request to the server and relays the response (or the state) back without storing any information. On the other hand, stateful systems expect a response, track information, and resend the request if no response is received.
What is the difference between stateful and stateless DDOS? ›
Stateful and stateless firewalls largely differ in that one type tracks the state between packets while the other does not. Otherwise, both types of firewalls operate in the same way, inspecting packet headers and using the information they contain to determine whether or not traffic is valid based on predefined rules.
What is the difference between stateful and stateless login? ›
The key difference between stateful and stateless is whether an application retains information about the current state of a user's interactions or if it treats each request as an independent, isolated transaction.
How does stateful authentication work? ›
Stateful Authentication
When a client tries to access the application with a given token, the application tries to retrieve session data from session storage, checks if the session valid, and then decides whether the client has access to the desired resource or not.
How does a WLC achieve stateful switchover for APs and clients? ›
How does a WLC achieve stateful switchover for APs and clients? A. The active WLC establishes a CAPWAP tunnel to the AP, and the standby WLC establishes a LWAPP tunnel to the AP.
What is the difference between failover link and stateful link? ›
The stateful failover link is used to replicate all the connections that are going through the active ASA. The failover link is used to replicate the configuration and the following info: *The unit state (active or standby).
Non-Stop Forwarding (NSF) and Stateful Switchover (SSO) are designed so a dual-Supervisor 6500 (or other device) can minimize packet loss during a Supervisor failure. They do this by keeping L2 and L3 state synchronized between the Supervisors.
What is the difference between failover link and stateful failover link? ›
The failover link is a dedicated connection between the two units. The stateful failover link is also a dedicated connection, but you can either use the one failover link as a combined failover/state link, or you can create a separate, dedicated state link.
What is the difference between SSO and RPR? ›
RPR can provide failover times around 2 minutes. RPR+ can provide failover times around 30 seconds. SSO can provide failover times around 1 seconds.
What happens during switchover? ›
A switchover guarantees no data loss and is typically done for planned maintenance of the primary system. During a switchover, the primary database transitions to a standby role, and the standby database transitions to the primary role.
What does RPS mean on Cisco switch? ›
Redundant Power Supply. There is a device that you can buy that will give external redundant power to some Cisco devices.
What is stateful failover? ›
Stateful failover ensures that traffic can continue without interruption. This is achieved by mirroring session state and persistence data to the standby Alteon, allowing the standby Alteon to continue forwarding traffic on existing connections, and ensuring persistence for new connections.
What does stateful mean in networking? ›
Stateful applications and processes allow users to store, record, and return to already established information and processes over the internet. In stateful applications, the server keeps track of the state of each user session, and maintains information about the user's interactions and past requests.
What is the purpose of a stateful firewall? ›
A stateful firewall is a kind of firewall that keeps track and monitors the state of active network connections while analyzing incoming traffic and looking for potential traffic and data risks.
What is the difference between stateful and non stateful firewall? ›
Stateful firewalls keep track of the state or context of connections by maintaining a state table. This allows them to differentiate between legitimate packets belonging to established connections and potentially malicious or unauthorized packets. Stateless firewalls do not track the state of connections.
