Connect. Secure. Manage.
Cisco ACI Troubleshooting
Investigate ACI endpoint, policy and forwarding faults by tracing application traffic through fabric state, contracts and external dependencies.
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.
Cisco ACI troubleshooting follows the path of a failed service through the fabric. A healthy dashboard does not prove that an app can reach what it needs. We check endpoint groups, policy and traffic flow against the reported fault. Evidence guides each step, with disruptive changes kept under an agreed approval process.
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.
Define the affected flow and incident window
We find the source and destination, required protocol or service, relevant tenant and the time the problem was observed. The scope distinguishes a single app failure from a broader network event. Working comparison flows are useful because they help isolate differences in endpoint attachment, contract policy or external routing.
Recent changes are reviewed without assuming they must be the cause. Application updates, virtual-machine movement, fabric policy changes and external firewall work can all influence the path. We reconcile timestamps and preserve the original evidence. If the historical record is incomplete, the conclusion states that limitation instead of treating the current healthy state as proof that no network problem occurred.
Standards & partnerships
Confidence in the team behind your network.
Cisco Partner
Cisco Meraki
Cyber Essentials
Cyber Essentials PlusMCI Network Services is operated by Proxar Ltd. Certifications apply to the certified legal entity and the scope of its certificates. View accreditation information
Verify endpoint attachment and learning
We check where the fabric believes the relevant endpoints are located and whether that matches the physical or virtual attachment. VLAN, domain and endpoint-group relationships are examined alongside host information. An endpoint appearing in inventory is not enough if it is learned in the wrong context or moves unexpectedly between locations.
Intermittent learning or duplicate-address conditions can produce inconsistent forwarding. We compare endpoint state over time and coordinate with the server or virtualisation team where host movement is involved. Clearing endpoint information may temporarily change the symptom but should not replace investigation of why the state became incorrect. The goal is a repeatable explanation and correction, not a cycle of manual resets.
A useful starting point
Not sure where to start?
Bring the requirement. We will help you define the engineering work.
Examine policy and routing as separate layers
We review the contracts and filters relevant to the traffic, including provider-consumer relationships and any broader policy options. Reachability and permission are not the same. A route can be present while a contract blocks the service, or a broad exception can allow more traffic than the customer intended. The actual policy relationships are checked rather than inferred from object names.
For traffic leaving the fabric, L3Out routing, external classification and return paths are included. A neighbouring firewall or router may be part of the failure even when the local fabric state is correct. We compare both sides of the boundary and avoid changing ACI policy simply to compensate for an unrelated external routing or app problem.
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 ↗Trace the forwarding path with proportionate diagnostics
We use the diagnostic capabilities supported by the actual ACI release and hardware to examine the affected path. Interface evidence, fabric faults, endpoint state and relevant packet observations are correlated. Diagnostic commands or captures that could affect performance are assessed before use, particularly on an already unstable production system.
Captures are authorised, filtered and handled according to the customer’s data needs. We record observation points and collection limitations so that missing or duplicated traffic is interpreted correctly. A useful investigation explains what the evidence shows, not merely that a large support bundle was collected. Where vendor assistance is needed, the bundle is scoped to the suspected issue and transferred securely.
Correct the cause through a controlled change
A proposed fix includes the hypothesis it addresses, the expected result and a rollback condition. We avoid broad policy relaxation or fabric-wide resets as routine first responses. Such actions can hide the original problem, expose unintended access and affect workloads that were functioning normally. Emergency workarounds require clear approval and a removal plan.
After the change, app owners repeat representative transactions and the network team checks the relevant policy and forwarding state. Negative tests are included where the remedy affects access boundaries. A successful single connection is not always enough to close an intermittent incident. An appropriate observation period may be needed to confirm that the fault no longer recurs under comparable conditions.
Deliver a clear incident record
The report separates root cause, contributing conditions, temporary workaround and permanent remediation. It links important findings to evidence and identifies unresolved questions. Documentation, monitoring or policy-ownership gaps become specific actions rather than vague recommendations to improve processes. This gives the customer a useful basis for future operations and vendor discussions.
MCI can investigate a focused ACI fault or review a fabric with recurring app problems. Related services include ACI policy design and ACI external routing. Share the affected flows, timestamps and available records through an agreed secure method. Access, diagnostic collection and production changes are separately authorised and limited to the scope needed to investigate the service.
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.
Existing customers should use their agreed support and escalation channels. This form is for service enquiries, not a monitored emergency ticket.
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