Subnet Calculator
Full /0–/32 support with RFC 3021-aware /31 handling.
/24
Network
—
Subnet mask—
Usable range—
Broadcast—
Wildcard—
Addresses / usable—
IPv4 Engineering
Subnet math, subdivision and real VLSM allocation.
Subnet Divider
Splits the calculated base network into equal child prefixes.
/26
Total subnets—
Usable each—
VLSM Planner
Enter multiple host requirements. Largest subnets are allocated first from the base network.
Allocated—
Remaining addresses—
LAN sizing reserves network + broadcast and therefore uses /30 as the smallest automatically allocated subnet. Use the subnet calculator directly for /31 point-to-point links.
Route Summarization
Range-aware aggregate calculation; input prefixes are not discarded.
Summary Route Engine
Each line may be a CIDR route or a host address. Hosts are treated as /32.
Summary route
—
Subnet mask—
Input address space—
Aggregate address space—
Additional covered space—
A single summary route is always a covering aggregate. If the inputs are non-contiguous, the result necessarily includes additional address space.
IPv4 Multicast L2 Mapping
RFC 1112 Ethernet mapping using the lower 23 multicast address bits.
Multicast IP → Ethernet MAC
Every Ethernet multicast MAC in this mapping can represent 32 IPv4 multicast groups.
IEEE MAC
—
Cisco dotted MAC—
Collision set—
IPv6 EUI-64
MAC-derived interface ID with U/L-bit inversion and /64 prefix validation.
Modified EUI-64 Generator
Accepts common MAC separators and compressed IPv6 notation. Prefix must be /64.
Interface ID—
Global unicast
—
Link-local
—
IPv6 Prefix / Subnet Planner
Normalizes an IPv6 prefix, calculates child-prefix capacity and lists the first child networks using native BigInt math.
Normalized parent—
Child subnets—
Addresses / child—
The table is intentionally capped at 32 child prefixes for mobile performance. The calculated count is not capped.
Protocol Lab
Fast protocol math and decision helpers for campus, routing, security and QoS work.
OSPF Cost
Classic cost = reference bandwidth ÷ interface bandwidth, minimum 1.
OSPF cost—
IOS/NX-OS reference cmd—
EIGRP Classic Metric
Default K-values only: K1=1, K3=1, K2=K4=K5=0. Wide metrics are not modeled.
Bandwidth component—
Delay component—
Classic metric—
BGP Best-Path Comparator
Common Cisco-style decision sequence. Multipath, AIGP, confederations and policy-specific exceptions are intentionally not modeled.
A
B
Selected path—
First decisive criterion—
STP Root Election
Compares effective bridge priority first, then MAC address.
Root bridge—
Reason—
HSRP / VRRP Virtual MAC
Generates the well-known virtual MAC from the redundancy protocol and group/VRID.
Virtual MAC
—
Valid group range—
Cisco Extended ACL ACE Builder
Builds one IOS XE / NX-OS style IPv4 ACE from CIDR inputs. Apply it to an ACL and interface only after reviewing direction and traffic impact.
ACE
QoS Rate / Burst / Serialization
Engineering math only; platform token-bucket implementation and minimum burst rules may differ.
Rate—
Burst (Bc)—
Serialization delay—
BGP Standard Community
Converts the classic 16-bit ASN:value form to the underlying 32-bit decimal value.
Community—
32-bit decimal—
Hex—
Nexus vPC / Dell VLT HA Pair Builder
Generates symmetric Peer A / Peer B foundations for a clean pair. Keepalive/backup reachability must exist independently from the peer interconnect.
PEER A
PEER B
VERIFY
For vPC, the builder uses the management VRF for peer-keepalive. For VLT, it uses the management VRF for the backup heartbeat. Confirm peer-link MTU, VLAN allowance, orphan-port handling, routing adjacencies and downstream multi-chassis LAG design before production use.
MTU & Encapsulation
Separates L3 tunnel overhead from L2 frame expansion.
Path MTU Budget
Base value is the underlay IP MTU — not the Ethernet wire-frame size.
Layer-2 Expansion
Tracked separately because common interface IP-MTU semantics exclude these bytes.
Each MPLS shim label adds 4 bytes between the Layer-2 header and the carried network-layer packet.
Calculated Budget
MSS assumes no TCP options: 20-byte TCP header.
L3 tunnel overhead—
Inner IP MTU—
TCP MSS IPv4—
TCP MSS IPv6—
L2 added bytes—
Do not blindly add GRE + VXLAN + IPsec unless that stack really exists on the packet path. The calculator intentionally allows stacking for nested overlays.
FRR BGP Unnumbered / EVPN
Interface-based eBGP template with explicit peer-group membership.
Fabric Inputs
Generates FRR syntax. SONiC VLAN/VNI configuration is release/platform dependent and is shown as intent only.
Generated FRR Configuration
Uses an external peer-group and interface-based unnumbered neighbors.
FRR
SONiC intent
Validate generated configuration against the FRR/SONiC release actually deployed before production use.
Leaf–Spine Fabric IP / ASN Planner
Allocates loopbacks, VTEPs and one /31 per leaf↔spine link. Useful before feeding device-specific values into Config Studio.
Devices—
Leaf↔spine links—
/31 addresses consumed—
Vendor Config Studio
Build clean-device configurations for Cisco IOS XE, Cisco NX-OS and Dell SmartFabric OS10 — with read-only pre-checks, configuration, verification, role presets and portable state export.
Deployment guardrail: generated CLI assumes a factory-default or otherwise known-clean device. Do not paste onto an unknown production switch without reviewing interface names, licensing, platform support, existing VLAN/VRF/routing state, and out-of-band rollback access. Management/AAA changes can lock you out.
1 · Platform & Identity
Reference profiles: IOS XE 17.18.x Catalyst 9000, NX-OS 10.6(x) Nexus 9000, Dell SmartFabric OS10 10.5.4+.
IOS XE 17.18.x
2 · Feature Scope
Only selected features are emitted. Keep the generated configuration minimal.
3 · Layer 2 Recipes
One object per line. Use the examples as the input grammar.
4 · Layer 3 & Routing Recipes
CIDR input is normalized to each platform's CLI style.
EVPN generation emits conservative L2-VNI building blocks for each platform. Routed overlays, anycast gateways, multihoming, VRF/L3VNI and fabric-specific policy still require topology-specific inputs.
5 · Generated Configuration
Review → copy → paste from console/OOB session → run verification commands → save only after validation.
PRE-CHECK · READ ONLY
CONFIG
VERIFY / POST-CHECK