Extreme Certified Professional - Extreme Switching key terms

The modular switch operating system used on Extreme's Summit, BlackDiamond, and VSP platforms. Configuration is organized into named VRs, VLANs, and ports, and is managed through CLI, EXOS APIs, or ExtremeCloud IQ.

Extreme's data center and campus switching platform family running VOSS rather than ExtremeXOS. It uses Shortest Path Bridging and Fabric Connect, so CLI syntax and architecture differ from Summit/EXOS devices.

Extreme's fixed-form campus access and aggregation switches running ExtremeXOS. Models differ in port count, PoE budget, uplink speed, and stacking support, which determines their role in a topology.

A separate routing and configuration context inside one ExtremeXOS switch, each with its own interfaces and routing table. VR-Default is preconfigured; additional VRs isolate management or customer traffic.

The default virtual router in ExtremeXOS that holds user data VLANs and their IP interfaces. Management access typically lives in VR-Mgmt, keeping administrative traffic separate from production forwarding.

The dedicated virtual router that carries out-of-band management interfaces on ExtremeXOS switches. It keeps SSH, SNMP, and NTP reachable even when data-plane VRs are being reconfigured.

The command-line interface for ExtremeXOS, entered in user or administrator mode. Commands use a hierarchical keyword structure, and configuration changes are applied immediately unless staged in a script.

The EXOS access level required for configuration changes such as creating VLANs or altering routing. User-level accounts can view status but cannot commit changes, enforcing role separation.

A VLAN dedicated to switch administration, with an IP interface reachable by SSH, SNMP, and syslog collectors. Isolating it from user VLANs limits exposure of management services.

Administrative access over a physically separate path such as a dedicated management port or console server. It remains usable when the data network or a VLAN is misconfigured.

A serial connection on the switch used for local CLI access, typically 9600 baud 8-N-1. It is the recovery path when IP management is unreachable or credentials are lost.

A saved copy of the running configuration stored on the switch or an external server. Snapshots allow rollback after a failed change and provide a baseline for comparing drift.

The loadable operating system file installed in a partition on the switch. Two partitions allow booting an alternate image if an upgrade fails.

One of two selectable storage areas holding an EXOS image. The switch can boot from either, so a new image is validated before the old one is overwritten.

A Layer 2 broadcast domain that groups ports independently of physical location. Frames stay within their VLAN unless a router interface forwards them, which contains broadcasts and separates traffic.

A switch port that carries 802.1Q frames with a VLAN identifier in the header, used for uplinks and trunk links. It can carry multiple VLANs simultaneously.

A port that sends and receives frames without a VLAN tag, typically connecting to an end device. Incoming untagged frames are assigned to the port's configured VLAN.

An inter-switch link that encapsulates frames with a VLAN tag so many VLANs share one physical link. Both ends must agree on the allowed VLAN list.

The VLAN whose frames are sent untagged on an 802.1Q trunk. Mismatched native VLANs on the two ends cause traffic to land in the wrong broadcast domain.

A Layer 2 protocol that blocks redundant links to prevent broadcast loops, electing a root bridge and computing a loop-free tree. ExtremeXOS supports STP, RSTP, MSTP, and EMISTP.

The switch elected as the reference point of the spanning tree, chosen by lowest bridge priority then lowest MAC address. All path costs are measured from it.

A configurable STP value, usually in increments of 4096, that influences root bridge election. Lower values make a switch more likely to become root.

An STP edge-port setting that moves an access port straight to forwarding, skipping listening and learning. It should only be applied to ports facing end stations, never to switch-to-switch links.

A protection feature that err-disables a PortFast port if it receives a bridge protocol data unit. It prevents an unauthorized switch from altering the spanning tree topology.

Two or more physical links bundled into one logical link to add bandwidth and redundancy. Traffic is distributed by a hash of frame header fields, so a single flow uses one member link.

IEEE 802.3ad protocol that negotiates and monitors LAG membership between peers. It detects misconfigured or failed member links and removes them from the bundle.

A link bundle configured manually on both ends without LACP negotiation. It works only if both sides match exactly, and a cabling error can silently create a loop.

The algorithm that maps a frame to one LAG member link, typically using source and destination MAC or IP plus port. Its choice determines how evenly traffic spreads.

A feature letting two switches present one logical LAG to a server or downstream switch. It provides link redundancy without relying on spanning tree blocking.

An IP address assigned to a VLAN so the switch routes between that VLAN and others. It acts as the default gateway for hosts in the VLAN.

A manually configured path to a destination network via a next-hop address or interface. It has an administrative distance and is preferred over dynamic routes only if that distance is lower.

A route matching 0.0.0.0/0 that forwards traffic with no more specific match. It is typically pointed at an upstream firewall or core router.

The set of known destinations with next hops and metrics that the switch consults to forward packets. The longest matching prefix wins.

A logical grouping of OSPF routers that shares link-state data. All routers in an area hold the same topology database, and area 0 forms the backbone.

A route automatically installed when an interface has an IP address and is up. It covers the interface's subnet and has the lowest administrative distance.

An ordered set of permit and deny rules applied to an interface or VLAN to filter traffic. Rules match on addresses, protocols, and ports, and the first match decides the action.

A named collection of rules in ExtremeXOS that can be applied to ports or VLANs for filtering, rate limiting, or marking. It is more flexible than a basic ACL.

Port-based access control where a supplicant authenticates to a RADIUS server through the switch before gaining network access. Unauthenticated ports stay restricted.

A protocol used by the switch to send user credentials to a central authentication server and receive accept or reject decisions, often with VLAN or policy attributes.

A username and password stored on the switch itself for CLI or management login. It is a fallback when external authentication servers are unreachable.

A restricted VLAN assigned to ports whose 802.1X supplicant has not authenticated. It typically allows only onboarding or remediation resources.

An unsolicited notification sent by the switch to a management station when a defined event occurs, such as a link change or threshold crossing.

A logging mechanism that sends event messages from the switch to local buffers or remote collectors. Severity levels let operators filter noise from critical faults.

A diagnostic feature that copies traffic from selected ports or VLANs to a monitoring port for capture and analysis. It is used to troubleshoot without disrupting production.

Remote Monitoring, a set of SNMP statistics and alarm groups that track counters such as CRC errors and utilization per interface for trend analysis.

An EXOS command that bundles configuration, logs, and diagnostic output into one file for vendor support. It captures state at the time of the fault.