GRE Tunnels - A Guide for Cisco and Junos Network Engineers

von Richard Nichols

336 Seiten, Taschenbuch

Kurzbeschreibung des Verlags

Generic Routing Encapsulation (GRE) TunnelsA Guide for Cisco and Junos Network EngineersYour tunnel shows up/up and the dashboard is green, yet the branch office can't open an email attachment. A routing adjacency flaps every forty seconds. IPv4 works but IPv6 hangs. Every network engineer meets these problems eventually, and this book shows you why they happen and how to fix them.Generic Routing Encapsulation is still the workhorse of enterprise WAN design. SD-WAN, cloud-native overlays and data center fabrics like VXLAN-EVPN have all arrived, but GRE remains the foundation for dynamic routing over public infrastructure, multipoint VPNs and secure site-to-site connectivity. This book explains how it works from the first byte to the last, then gives you production-ready configurations for both of the platforms you're most likely to run.The early chapters build a vendor-neutral model you can use on any platform:Overlay and underlay design. Learn where GRE fits next to IP-in-IP and VXLAN, and why enterprise WANs and modern data centers chose different overlays.The byte-level math. Work out tunnel MTU and TCP MSS for plain GRE, GRE over IPsec with AES-CBC and AES-GCM, transport and tunnel mode, NAT traversal, and dual-stack IPv4/IPv6 overlays. You'll see exactly where the familiar 1400/1360 values come from and when they aren't safe.Security integration. Compare crypto maps with tunnel protection, VTIs with GRE, and the structural difference between how Cisco IOS XE and Juniper Junos apply IPsec. That difference confuses many engineers who work with both vendors.Real-world pitfalls. Diagnose recursive routing loops, the "dead peer illusion" of a stateless protocol, PMTUD black holes, and firewalls that block GRE because they're filtering ports instead of IP protocol 47.The later chapters move from theory to the command line. For Cisco IOS XE, you'll build a point-to-point GRE tunnel in three stages: plain GRE, then IPsec protection, then OSPF. You'll then deploy DMVPN with NHRP Phase 3 shortcuts and finish with a dual-hub, dual-cloud design using BFD for sub-second failover. For Juniper Junos, you'll follow the same staged build with gr- and st0 interfaces and front-door routing instances, then build certificate-based Auto Discovery VPN (ADVPN) and a dual-hub high-availability design. Each configuration chapter has a matching troubleshooting chapter with a structured checklist: isolate the underlay, check the cryptography, then audit data-plane liveness.Every example uses a consistent lab addressing plan, and every design decision is explained, so you understand why each command is there. Appendices provide command references for both vendors, a glossary and an index.This book is for:Network engineers who support mixed Cisco and Juniper environmentsArchitects designing or migrating WAN overlays

• Themen: Informatik und Informationstechnologie Computernetzwerke und maschinelle Kommunikation Netzwerkstandards und Netzwerkprotokolle
• ISBN: 9798183009057
• Sprache: Englisch
• Erscheinungsdatum: 29.10.2026
• Größe: 280 x 210 mm
• Verlag: C Snyder