How Servers Share an IP Address for High Availability
Cisco's 2017 patent describes a system where multiple servers can share a single virtual IP address to ensure an application stays online even if one server fails.
Original patent title: “Redundancy network protocol system”
Cisco's 2017 patent describes a system where multiple servers can share a single virtual IP address to ensure an application stays online even if one server fails. Granted to Cisco Technology Inc in 2017 with 20 claims and 4 forward citations, and it is expected to expire in 2033.
Coverage
What does this patent actually cover?
This patent details a system where servers work together to keep an application running. A 'profile' for an application is shared between servers, and this profile includes a virtual IP address (VIP) that clients use to connect. Each server has a 'priority' level. The system automatically picks the server with the highest priority to handle client requests. If the active server fails, another server with a high enough priority takes over. The system constantly checks if servers are still 'neighbors' by sending and receiving status messages. It also tracks how many other servers are sending status messages to each server. If the counts don't match, priorities might be adjusted. For example, if Server A is supposed to get status messages from 3 other servers but only gets them from 2, its priority might decrease.
The gap
What does this patent NOT cover?
- Systems where servers are not at least one router hop away from each other.
- Protocols that do not use a virtual IP address shared between servers.
- Systems that do not involve comparing priorities between servers to select an active one.
- Methods that do not monitor server health via status messages.
- Applications that do not require high availability.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The innovation lies in how servers actively manage each other's status and priorities, even across multiple network hops. It's not just about one server failing, but about a dynamic system where servers collaborate to maintain a single point of access (the virtual IP) for an application, adapting to changing network conditions and server availability.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
High-availability clusters for critical servers
Network load balancing solutions
Virtual IP address management in data centers
Why it matters
The bigger picture
This patent is part of the foundation for ensuring critical applications and services remain accessible. It addresses the need for 'high availability' in networking, meaning services should be continuously operational. This is crucial for everything from online banking to cloud services, where downtime can be very costly.
Filed
September 17, 2013
Granted
February 14, 2017
Market context
Who's building on this
Companies in this space
Cisco, the assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, continues to be a major player in networking hardware and software where such redundancy protocols are essential. Competitors in the enterprise networking space, including companies like Juniper Networks and Arista Networks, implement similar high-availability features in their routing and switching products.
Market impact
Patents like this contribute to the development of robust networking infrastructure. They enable the creation of resilient systems that are fundamental to modern cloud computing and enterprise IT, ensuring services stay online and accessible to users, thereby supporting the growth of online services and e-commerce.
Claim 1 — Plain English
What this patent covers
This patent details a system where servers work together to keep an application running. A 'profile' for an application is shared between servers, and this profile includes a virtual IP address (VIP) that clients use to connect. Each server has a 'priority' level. The system automatically picks the server with the highest priority to handle client requests. If the active server fails, another server with a high enough priority takes over. The system constantly checks if servers are still 'neighbors' by sending and receiving status messages. It also tracks how many other servers are sending status messages to each server. If the counts don't match, priorities might be adjusted. For example, if Server A is supposed to get status messages from 3 other servers but only gets them from 2, its priority might decrease.
The clever bit
The innovation lies in how servers actively manage each other's status and priorities, even across multiple network hops. It's not just about one server failing, but about a dynamic system where servers collaborate to maintain a single point of access (the virtual IP) for an application, adapting to changing network conditions and server availability.
What it does not cover
- Systems where servers are not at least one router hop away from each other.
- Protocols that do not use a virtual IP address shared between servers.
- Systems that do not involve comparing priorities between servers to select an active one.
- Methods that do not monitor server health via status messages.
- Applications that do not require high availability.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
PatentBrief Score
Impact Score
Moderate
Citation count
14/40
Early citations
Claim breadth
13/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
10/20
Granted 5–10 years ago
Assignee scale
20/20
Major company or institution
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$55K – $175K
Midpoint $109K · 7.2 yr remaining · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Patent Claims
0 independent claims · 1 dependent
Claims are the legal boundaries of the patent. An independent claim stands alone. A dependent claim adds limitations to its parent, narrowing — but not broadening — the scope.
The original legal language
Original claims
20 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Evens, T. (2017). How Servers Share an IP Address for High Availability (U.S. Patent No. 9,571,603). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/9571603/redundancy-network-protocol-system
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Servers Share an IP Address for High Availability cover?
Cisco's 2017 patent describes a system where multiple servers can share a single virtual IP address to ensure an application stays online even if one server fails.
Who owns patent US 9571603?
Cisco Technology Inc owns this patent, granted in 2017.
When does this patent expire?
This patent is expected to expire on September 17, 2033, when the invention enters the public domain.
What is patent US 9571603 cited by?
This patent has been cited by 4 later patents that build on its ideas.
What problem does this patent solve?
This patent is part of the foundation for ensuring critical applications and services remain accessible. It addresses the need for 'high availability' in networking, meaning services should be continuously operational. This is crucial for everything from online banking to cloud services, where downtime can be very costly.
What does this patent NOT cover?
Systems where servers are not at least one router hop away from each other.
Same assignee
More from Cisco Technology Inc
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