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diff --git a/src/content/cidr-guide.md b/src/content/cidr-guide.md index 1ba0da7..93e6186 100644 --- a/src/content/cidr-guide.md +++ b/src/content/cidr-guide.md @@ -1,21 +1,25 @@ +--- +title: "Subnet Guide — IP Ranges and Masks" +description: + "Free interactive CIDR calculator and comprehensive guide covering subnetting, IP ranges, subnet masks and addressing." +--- + ## What is CIDR? **Classless Inter-Domain Routing (CIDR)** is the system that replaced the old class-A/B/C scheme in 1993. A network is written as ``` -address/prefix-length → 10.0.0.0/24 +address/prefix-length → 10.0.0.0/24 ``` The *prefix length* (the number after the slash) tells routers how many of the 32 bits belong to the network portion: -* `10.0.0.0/24` → 24 network bits + 8 host bits → **256** addresses (254 usable) -* `10.0.0.0/30` → 30 network bits + 2 host bits → **4** addresses (2 usable) +* `10.0.0.0/24` → 24 network bits + 8 host bits → **256** addresses (254 usable) +* `10.0.0.0/30` → 30 network bits + 2 host bits → **4** addresses (2 usable) CIDR lets ISPs advertise aggregated “supernets” such as `203.0.113.0/22` instead of listing a thousand individual /24 routes—shrinking global routing tables and conserving address space. ---- - ## CIDR → IP Range Converter Paste any block—say `192.168.15.64/27`—into the calculator. Behind the scenes it: @@ -26,8 +30,6 @@ Paste any block—say `192.168.15.64/27`—into the calculator. Behind the scene Hit **Copy Share Link** to bookmark or send an exact result. ---- - ## Subnetting Tutorial — Quick Steps Subnetting seems daunting until you break it into four predictable moves: @@ -37,13 +39,15 @@ Subnetting seems daunting until you break it into four predictable moves: 3. **List subnet starts** 0, 64, 128, 192 4. **Pick your block** Usable hosts = block size − 2 (62 in a /26) -> **Example** -> Split `172.16.0.0/16` into at least 10 equal subnets. -> *Need ≥10 blocks → 4 extra bits (2⁴ = 16)* -> New prefix = **/20**. Each /20 holds 4094 hosts. -> Ranges begin 172.16.0.0, 172.16.16.0, 172.16.32.0 … to 172.16.240.0. +### Example ---- +Split `172.16.0.0/16` into at least 10 equal subnets. + +*Need ≥10 blocks → 4 extra bits (2⁴ = 16)* + +New prefix = **/20**. Each /20 holds 4094 hosts. + +Ranges begin 172.16.0.0, 172.16.16.0, 172.16.32.0 … to 172.16.240.0. ## IPv6 Subnetting Basics @@ -58,8 +62,6 @@ The slash notation is identical in IPv6—just with 128-bit addresses. Toggle **IPv6** in the calculator and try `2001:db8::/48` to explore the range graphically. ---- - ## Further Reading & Tools * RFC 4632 — *Classless Inter-Domain Routing for IPv6* |