Connect. Secure. Manage.
Data Centre Layer Two Extension
Evaluate whether applications genuinely need Layer 2 extension, then design supported Cisco connectivity with explicit loop and failure-domain controls.
Devices supported
across the UK
Client locations
supported
Traffic handled
at peak time
Average
response time
Average response is not a resolution time or a contractual guarantee. Support scope and response commitments are agreed for each engagement.
Data centre Layer Two extension preserves selected network segments across locations, but it also carries their dependencies and potential faults beyond the original site. MCI Network Services assesses whether extension is genuinely required before designing a supported Cisco implementation. We help customers distinguish a temporary migration convenience from a long-term application requirement and make the consequences of loops, partitions and gateway placement explicit.
Workload-led design
Start with application, compute and storage dependencies rather than the switch model.
Clear failure domains
Understand which links, devices and sites can fail together.
Operational clarity
Make fabrics, external routing and management responsibilities supportable.
Challenge the requirement constructively
A request to keep the same IP addresses can arise from application constraints, a relocation deadline or a wish to simplify migration. We examine the reason with the application and platform owners. Sometimes routed connectivity and planned addressing changes provide a cleaner solution; sometimes a bounded extension is justified. The decision is based on the service, not on a blanket rule that extension is always good or always wrong.
The assessment identifies which segments need to cross sites and which do not. Extending every VLAN because a few applications require it increases operational scope unnecessarily. We record endpoint locations, gateway ownership, supporting services and the period for which extension is needed. This gives the customer a specific design problem rather than an open-ended request to make two data centres behave as one.
Standards & partnerships
Confidence in the team behind your network.
Cisco Partner
Cisco Meraki
Cyber Essentials
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Understand the enlarged failure domain
Layer 2 extension can allow broadcast, unknown-destination and endpoint-learning effects to influence more than one location. The exact behaviour depends on the chosen architecture and controls. We review how loops are prevented, how forwarding state is maintained and what happens when transport is interrupted. The design must be evaluated as a whole, not only at the local switch ports.
A partition can create application consequences that network configuration alone cannot resolve. Systems at separate sites may continue operating with incomplete communication. We involve application and storage owners in decisions about failover, isolation and recovery authority. Network extension is not presented as proof that a distributed application is safe from split-brain or data-consistency problems.
A useful starting point
Not sure where to start?
Bring the requirement. We will help you define the engineering work.
Select a supported transport and encapsulation model
We assess the Cisco platforms, software and available inter-site transport against the requirement. Supported EVPN-based approaches may be appropriate in some environments, while other designs need different treatment. We verify feature combinations, scale and migration compatibility rather than assuming that any Nexus switch can provide any form of extension.
Transport capacity, MTU, latency and diversity are documented. Encapsulation requirements must be met across the complete path, and the surviving link must carry the agreed traffic during a failure. We also assess encryption separately from private transport. A private cross-connect or carrier service should not be described as encrypted unless the deployed design actually provides that protection.
Different environments. The same care.
Built around the work
your network supports.
Finance, banking and the wider private sector. We start with the systems and people that depend on your connections.
Finance & banking
Market-data paths, routing and provider coordination on clients’ behalf.
Financial-market services ↗Offices & multi-site teams
Reliable access between people, workplaces and business applications.
Office network design ↗Data centres & cloud
Network boundaries, workload connections and operational ownership.
Data centre networks ↗Place gateways and security controls carefully
The location and ownership of default gateways influence both normal traffic and recovery. We define where routing occurs and how endpoint neighbour information changes during migration or failover. Competing gateway implementations are not enabled casually. Any supported coexistence arrangement has explicit configuration, scope and acceptance tests.
Security paths are reviewed in both directions. Extending a subnet can move traffic away from an inspection point or change how a firewall sees the source and destination. We identify the required controls and the conditions under which traffic must remain local or cross sites. The customer approves those boundaries before the extension becomes part of production connectivity.
Test the application requirement and the failure behaviour
Acceptance includes representative endpoint communication, gateway access, large-packet behaviour and the intended security restrictions. We test the actual reason for extension, such as a controlled workload move, rather than relying only on a ping between switches. Platform and application teams confirm the service result.
Authorised fault scenarios examine transport loss, restoration and relevant endpoint movement. We record what was observed and which conditions remain untested. A design may need a specific operational response when sites become isolated; that response is documented with its owner. The handover avoids a broad availability promise that exceeds the tests and supporting design evidence.
Give temporary extension an exit plan
Migration-only links should have clear removal criteria. We identify the workloads and services that must move before the extension can be withdrawn, then plan the routing and gateway changes needed to restore the intended boundaries. Leaving a temporary bridge indefinitely can preserve risks long after its original benefit has disappeared.
MCI can assess an existing extension or design a controlled transition as part of data centre interconnect work. Our relocation networking service covers the associated cutover planning. Provide the application requirement, current topology and intended duration to begin. We will identify the supported options and the responsibilities needed to keep the extension bounded and operable.
Talk to a specialist
What does your network need next?
Tell us what you are planning, changing or trying to improve. We will help define a practical next step and the engineering scope.
+44 203 196 6566Choose option 1
sales@proxar.co.ukUK-wide service.
Most of our engineers are based in Kent, with a focus on London, Sussex, Essex and Berkshire.
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