Invalidity dossier
US 6741592
Private VLANs
Current assignee: Cisco Systems Inc
Added 9/23/2026, 6:23:17 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US6741592B1, "Private VLANs"
Title: Private VLANs
Patent number: US6741592B1
Application number: US09/575,774
Inventors: Thomas J. Edsall, Marco Foschiano, Michael Fine, Thomas Nosella
Original assignee: Cisco Technology Inc; current assignee listed as Cisco Systems Inc
Priority/filing date: 2000-05-22
Publication (grant) date: 2004-05-25
Legal status: Expired – Lifetime (anticipated expiration 2020-05-22)
Classification: H04L12/46 (Virtual LANs, VLANs)
Purpose. The invention addresses the limited number of Layer 3 subnets available for keeping users' traffic separate on shared networks. It proposes using a Layer 2 switch, or bridge, to separate users' traffic via Virtual Local Area Networks (VLANs) defined within the switch, to scale to many users.
Plain-language scope (as described). The patent defines three new port types—promiscuous, isolated, and community—and three internal VLAN types—primary, isolated, and community. Promiscuous ports connect to Layer 3 or Layer 4 devices such as routers, load balancers, administrative workstations, and backup devices. Isolated and community ports connect to individual users' servers. A primary VLAN connects to all promiscuous, isolated, and community ports and carries packets one way from promiscuous ports to isolated/community ports; isolated or community ports cannot forward externally received traffic to the primary VLAN. An isolated VLAN connects isolated ports to promiscuous ports, one way, and delivers no packets to another isolated port. A community VLAN connects a group of community ports plus all promiscuous ports; an isolated port cannot transfer packets to another isolated port, whereas a community port can transfer packets to a designated number of community ports.
Source: https://patents.google.com/patent/[US6741592](/patent/US6741592)/en
What the excerpt does not establish: It does not establish the full claims, specification, or figures; the community-VLAN description is truncated. Litigation, reassignments beyond those listed, validity, and prior art are outside this overview and were not researched.
Generated 10/1/2026, 9:42:46 PM
Cases on file (0)
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Litigation summary
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Proceedings on file (0)
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No PTAB proceedings on file. This patent has not been challenged via IPR, PGR, or CBM. The absence is itself a signal — well-asserted patents eventually attract IPRs. The LLM analysis below may surface filings the ODP feed hasn’t indexed yet.
PTAB challenges
AIA trial proceedings at the USPTO Patent Trial and Appeal Board — IPR, PGR, and CBM. Petitioners, judge panels, claim-level invalidation outcomes from Final Written Decisions, and Federal Circuit appeals. The single most important defensive datapoint after litigation history.
Assignment history
Inventors, original assignee, and the chain of ownership recorded with the USPTO — including the correspondent attorney who recorded each assignment, since shell-LLC chains often share one repeat-player attorney even when the entity names look unrelated. Surfaces NPE / patent-troll patterns: shell-entity transfers, known asserters in the chain, repeat correspondent fingerprints, pre-litigation assignments, and bankruptcy fire-sales.
Prior art
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Obviousness
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Extensions
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Derivative works
Defensive disclosure: derivative variations of each claim designed to render future incremental improvements obvious or non-novel.