Peer1IX
Internet Exchange
Services

Interconnection

Internet ExchangeMicro PoPsEdge Data Centers

Network Services

Data Center to Data CenterVirtual Connectivity HubData Center to CloudCloud to CloudPeer1ix Cloud RouterPeer1ix Virtual EdgeNAT GatewayPeer1ix PortVirtual Cross Connect

Security Services

DDoS ProtectionPeer1ix FWaaSIPsec Tunnel

Cloud Interconnect

Cloudflare Network Interconnect
Locations
Network toolsAll-in-One Network ReportBGP Looking GlassRPKI ValidatorBGP Security & Hijack CheckIP WHOISAS WHOISBGP Route ExplorerASN InsightsBGP Hijacks & Route LeaksInternet Outage TrackerCountry Internet InsightsTop Domains RankingDNS LookupSubnet CalculatorWhat Is My IP
BlogAboutContact Get connected

Shared Address Space 100.64.0.0/10: What It Is and Why It Exists

· 1 min read · Peer1IX Team

Shared Address Space 100.64.0.0/10: What It Is and Why It Exists

The 100.64.0.0/10 range was set aside specifically for carrier-grade NAT. A short explainer and some common pitfalls.

Why a special range

Before 2012, operators deploying CGNAT used RFC 1918 private ranges like 10.0.0.0/8 between the subscriber’s home router and the CGNAT. But home networks use those same ranges, causing conflicts. RFC 6598 set aside 100.64.0.0/10 as shared address space for this purpose.

How it is used

Subscribers’ routers receive addresses from 100.64.0.0/10 on their WAN side. CGNAT translates them to public addresses.

Keep it internal

Shared address space must never be announced on the internet. Treat it as a bogon and filter it on external BGP sessions — as Peer1IX route servers do.

Pitfalls

Some applications treat 100.64.0.0/10 as public and behave unexpectedly. Test key applications in a CGNAT environment.

Check whether any range is bogon space with our BGP security tool.

RFC 6598shared address spaceCGNAT

Keep reading

Network Engineering

Performance Tuning for High-Throughput IPsec

Encryption costs CPU, and tunnels can underperform. Practical ways to get more throughput from IPsec.

 Network Services

When to Choose Public IPv4 Over NAT for Business Customers

NAT suits most residential users. Business customers often need dedicated public addresses. How ISPs can segment offerings sensibly.

 Network Engineering

IPv6 Across Clouds and Sites With a Virtual Router

IPv6 adoption is rising across clouds and Indian networks. How to extend dual-stack routing across your hybrid environment.