Topic

Subnetting practice labs

24 hands-on Subnetting scenarios you build in your own Cisco Modeling Labs instance and grade against the answer key. Subnetting configuration and troubleshooting practice for CCNA and CCNP.

One /24, carved into right-sized subnets — the reference wiring for Subnetting & IP Addressing, not a specific lab.

Included with a subscription

BeginnerDailyLocked

CCNA Foundations: IPv6 Addressing — Put a /64 on the Wire

Bring IPv6 up alongside the already-working IPv4 baseline. You will enable IPv6 unicast routing on both routers, put a unique 2001:db8::/64 on each site LAN, put a /127 on the router-to-router transit, and address the dual-homed workstation on both of the LANs it is plugged into plus its IPv6 default route. Verify that IPv6 reaches both on-link gateways and, through the default route, the near router's transit address — while the far router's transit address stays unreachable over IPv6 and reachable over IPv4, because no IPv6 routing between the sites exists yet.

CCNA50 min4 objectives

AdvancedLocked

IP Addressing Troubleshooting Capstone

Advanced IP addressing capstone, run as a fault hunt. A branch build has been handed over and nothing quite works: one LAN cannot reach its gateway, a transit link behaves as though the two ends are on different networks, one router will not accept traffic on a point-to-point link, and two devices answer to the same loopback. You get symptoms and the required end state — no fault list. Every fault is an addressing decision that looks plausible until it is checked against the mask.

CCNA55 min5 objectives

IntermediateLocked

CCNA Lab: VLSM Right-Sizing from One /24

Practice deterministic VLSM planning and interface addressing on two Cisco IOS routers. Starting from a single /24, allocate three right-sized IPv4 subnets (two LANs represented by loopbacks and one router-to-router WAN) and configure exact interface addresses and masks. No routing protocols or static routes are configured; verification focuses on directly connected reachability and show commands.

CCNA40 min4 objectives

IntermediateLocked

Secondary IP on a LAN Interface

Configure a Cisco IOS router to host two IPv4 /24 subnets on a single physical LAN interface using a secondary address. Verify directly-connected reachability only (no routing protocols, no static routes). This simulates a readdressing coexistence period where both old and new subnets must operate concurrently on the same segment.

CCNA40 min4 objectives

BeginnerLocked

CCNA Lab 2: Subnet a /24 into Four /26s

Hands-on IPv4 subnetting and interface addressing on three IOS routers and one client. You will split a /24 into four equal /26s, assign the correct /26 mask to each link, and configure deterministic lowest-usable addressing on router interfaces. No routing protocols or static routes are used; verification is strictly directly-connected reachability.

CCNA45 min5 objectives

IntermediateLocked

Point-to-Point Links with /30 and /31

Build confidence addressing IPv4 point-to-point WAN links on Cisco IOS using /30 and /31 masks. Two routers are connected by two parallel links: one classic /30 and one RFC 3021 /31. No routing protocols or static routes are configured — the goal is deterministic, correct interface addressing and verification of directly connected reachability. A small LAN off R1 with two hosts allows additional verification (host-to-gateway only).

CCNA35 min4 objectives

AdvancedLocked

Lab 9: Dual-Stack IPv4/IPv6 Addressing on IOS

Configure and verify dual-stack IPv4 and IPv6 addressing on Cisco IOS router interfaces. R1-R2 share a /30 IPv4 and /64 IPv6 point-to-point transit, while R1 provides a dual-stack user LAN gateway. No routing protocols or router static routes are permitted; verify only directly connected reachability.

CCNA45 min5 objectives

AdvancedLocked

IPv6 Link-Local Addressing

Advanced IPv6 interface addressing on Cisco IOS routers. Configure explicit, predictable IPv6 link-local addresses alongside global unicast addresses on a point-to-point router-to-router link. Validate with show commands and neighbor pings using the link-local as the destination, and confirm host-to-gateway reachability on local LANs. No routing protocols or static routes are used; focus is strictly on interface IPv6 addressing mechanics.

CCNA40 min5 objectives

AdvancedLocked

IPv6 Addressing with EUI-64

Configure IPv6 global unicast on a router-to-router link using EUI-64-derived interface IDs. Enable IPv6 unicast routing, set explicit link-local addresses, and verify that each router auto-forms its 64-bit interface ID from the MAC (FFFE insertion with U/L bit flip). Validate directly-connected reachability only. No routing protocols or static routes.

CCNA35 min5 objectives

IntermediateLocked

IPv6 Global Unicast Addressing

Enable IPv6 forwarding and configure IPv6 global unicast addresses on directly connected links only. No routing protocols or static routes. Verify that each device can reach only its directly connected neighbors using IPv6.

CCNA35 min4 objectives

BeginnerFree2026-07-04

CCNA L1: Interface Addressing and Verification

Beginner CCNA lab (1 of 10) focused on configuring and verifying IPv4 interface addressing on Cisco IOS routers. Learners assign given /24 addresses to two router interfaces and validate directly-connected reachability. No routing protocols or static routes are configured in this lab.

CCNA25 min4 objectives

Free with an account

IntermediateLocked

DHCP: Serving Two Subnets from Two Pools

Build and verify two independent DHCP address pools on a single Cisco IOS router, each serving a different LAN. Two Alpine Linux clients obtain leases from their respective pools via directly attached access switches. You will configure the pools, excluded addresses, default gateways, DNS, and domain names, then verify with IOS show commands and Linux tools. The focus is deterministic router DHCP configuration; clients lease dynamically and are verified rather than graded.

CCNA45 min5 objectives

IntermediateLocked

Router Interface as a DHCP Client (IOS-to-IOS)

Configure an IOS router as a DHCP server and have another IOS router obtain its uplink address dynamically via DHCP on a shared LAN. Validate the lease from both the client and server perspectives and test reachability from attached hosts.

CCNA35 min4 objectives

BeginnerLocked

DHCP Exclusions: Reserved Statics on a Single LAN

Configure an IOS-XE router as a DHCP server with a correctly scoped pool and an excluded-address range that protects the gateway and a reserved static server (.10). Two Alpine clients obtain addresses dynamically from the remaining range (starting at .11). Verify leases, confirm the excluded count, and ensure the reserved static never appears as a DHCP binding.

CCNA35 min5 objectives

IntermediateLocked

NAT Selection with an ACL: PAT a Single Host Only

Configure PAT on an edge router so only PC-A is translated using a standard ACL as the traffic selector. PC-B remains untranslated and fails to reach the ISP, illustrating that NAT occurs only for traffic explicitly matched by the ACL. Validate using host pings and IOS show commands, and interpret ACL hit counters and NAT tables.

CCNA45 min5 objectives

AdvancedLocked

ACL Troubleshooting Capstone: Classic Faults, NAT, Placement

Advanced ACL and NAT capstone, run as a fault hunt. A branch site was cut over last night and the policy does not behave: the flow that should be blocked gets through, other traffic does not come back at all, and nobody recorded what changed. You get symptoms and the required end state — no fault list. The faults span all three routers and include a shadowed ACE and a policy applied on the wrong side of NAT, so translated addresses hide the very hosts the rules name. Expect fixing the first one to change the symptom rather than clear it.

CCNA75 min5 objectives

BeginnerLocked

Extended ACL Fundamentals: Permit HTTP, Deny Others

Deploy a numbered extended ACL on a router-on-a-stick topology to allow HTTP from a single approved client to a web server while denying all other TCP attempts to that server from the same user VLAN. Apply the ACL inbound near the source, verify with real client traffic, and troubleshoot using ACL hit counts and test flows.

CCNA50 min5 objectives

BeginnerDailyLocked

IPv4 Addressing Fundamentals: Interfaces, Gateways & Reachability

Beginner CCNA lab focusing on IPv4 addressing and basic Layer 3 verification on a small branch network. You will assign IP addresses to router interfaces, confirm end-host default gateways, and verify connected reachability using host-based pings. You will also learn to read 'show ip interface brief' and 'show ip route' to confirm operational state before any routing beyond directly-connected networks is configured.

CCNA50 min5 objectives

IntermediateLocked

CCNA: ACL Placement – Std Near Dest, Ext Near Source

Dual-router Branch/HQ lab with a branch client and an HQ server. You will apply an extended IPv4 ACL inbound near the source on the Branch LAN to block specific traffic (TCP/80) while permitting others (ICMP), and a standard IPv4 ACL outbound near the destination on the HQ LAN to admit only the approved source. Validate from real hosts, confirm ACL hitcounts, and keep inter-site connectivity via static routes over a /30 transit.

CCNA55 min4 objectives

IntermediateLocked

ACL App Filter: Permit SSH/HTTP, Block Telnet/ICMP

Build a two-router, one-access-switch lab with a client and a server. Establish basic IP connectivity with static routing, then implement an extended IPv4 ACL inbound on the client-facing interface to permit SSH and HTTP to the server while denying Telnet and ICMP echo. Validate from the client and review ACL hit counters for proof.

CCNA55 min5 objectives

AdvancedLocked

ACL Segmentation Policy on Multi-LAN Router

Deploy and verify multiple IPv4 ACLs on a single router that terminates three distinct LANs (Client, Server, and Management). You will place an extended ACL inbound on the Client interface to allow only specific services to the Server and block access to Management, a standard ACL outbound on the Management interface to enforce destination-side protection by source, and a VTY access-class to restrict router SSH to the Management subnet only. Validate with end-host tests that permitted flows succeed while denied flows are provably blocked, and use ACL hit counts and logs to troubleshoot.

CCNA70 min5 objectives

BeginnerLocked

CCNA Default Routes: Edge-to-Core Gateway of Last Resort

Configure a default route on a branch edge router and a return static route on an upstream core router to enable full bidirectional connectivity between a stub branch LAN and a core server LAN. Verify the S* default route, gateway of last resort, and end-to-end reachability from real hosts. Troubleshoot missing default or return paths.

CCNA40 min5 objectives

IntermediateLocked

CCNA Static Routing: Host vs Subnet (/32 vs /24)

Deploy a compact two-site topology with a WAN core and two end hosts to practice IPv4 static host routes (/32) versus subnet routes (/24). You will configure a specific /32 host route to steer one destination host over the direct R1–R3 path while a broader /24 for the same remote LAN is sent via the R1–R2–R3 core. Validate with show commands and traceroute, then troubleshoot longest-prefix match and return-path issues.

CCNA55 min4 objectives

AdvancedLocked

CCNA Static Routing: 3-Router Full-Mesh

Design and implement a 3-router full-mesh with two edge LANs using static IPv4 routes only. Edges use primary defaults toward the core plus floating (higher AD) backup defaults; the core uses specific routes for the edge LANs. Validate bidirectional reachability, path choice, and failover behaviors from real hosts.

CCNA75 min5 objectives

Practicing IPv4 subnetting and addressing on Cisco Modeling Labs

Why it matters, and what these labs cover.

Subnetting is the one CCNA skill that shows up inside every other topic. You cannot configure an interface, write an ACL, summarise a route or design an OSPF area without deciding where a network splits and which addresses are usable. Most people learn it as arithmetic on paper and then discover that the exam and the job both ask a harder question: given these host counts and this address space, what should the plan actually be — and does the configuration you just typed match it?

These labs make subnetting a configuration exercise rather than a worksheet. You'll take an address block and carve it with VLSM to fit departments of different sizes, assign the right addresses and masks to interfaces, use /30 and /31 on point-to-point links and see why the /31 exists, and then prove the plan works with end-to-end connectivity rather than by re-checking your maths. Wildcard masks get their own treatment, since an ACL and an OSPF network statement both need them and both punish an off-by-one. Grading checks the exact addresses and masks the plan requires, so an address that is inside the right subnet but wrong for the design does not slip through.

Frequently asked questions

Do I need to be fast at subnetting before starting?

No. These labs give you the arithmetic in a context that makes it stick, which is generally faster than drilling tables. If you are starting cold, the subnet calculator in the free tools section will keep you moving while the pattern settles.

What is the difference between a subnet mask and a wildcard mask?

A subnet mask marks the network bits with ones; a wildcard mask is effectively its inverse and marks the bits that are allowed to vary. ACLs and OSPF network statements take wildcard masks, which is why an address that works on an interface can be rejected there.

Why would I use a /31 on a point-to-point link?

A /30 spends four addresses to give you two usable ones. On a link with exactly two routers there is no need for a network or broadcast address, so a /31 gives the same two usable addresses out of two. The labs configure both so the saving is concrete.

Learn Subnetting

Study the theory behind these labs — the concept explainer and step-by-step guides.

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