TSHOOT – GRE DEEP DIVE!!! MTU / Fragmentation / TCP-MSS / PMTUD / Recursive Routing / Interface States / must know information for exam day!

The graphic above shows a VPN Tunnels two modes (Transport and Tunnel), along with how their payloads differ when configured with AH (Authentication only) and ESP (Encryption) on the tunnel, and what protocols correlate with all of it. The basics of GRE and IPSec Tunnel Modes and Packet Formats Basic GRE tunnel configuration has absolutely … Continue reading TSHOOT – GRE DEEP DIVE!!! MTU / Fragmentation / TCP-MSS / PMTUD / Recursive Routing / Interface States / must know information for exam day!

VPN: DMVPN, NHRP, and mGRE – Brief initial configuration review, verification review, and a link to all the gritty details!

Since we are now efficient at all things GRE and IPSec VPN at this point, that makes for a smooth transition into DMVPN , though I want to be crystal clear that the ROUTE Blueprint mentions only "Describe DMVPN (Single Hub)" so I will not be configuring it all over again, I do have a … Continue reading VPN: DMVPN, NHRP, and mGRE – Brief initial configuration review, verification review, and a link to all the gritty details!

VPN: DEEP Dive into GRE over IPSec configuration, explanation, and very easy actually once you are familiar with GRE and IPSec!

So this is very odd to me after going through the last two posts of GRE and IPSec configuration, however once I found good information, configuration was a breeze. **PLEASE READ EXAM DAY NOTE AT END OF POST FOR SCENARIOS WHERE THE ROUTES HAVE TO BE IN THE DYNAMIC ROUTING PROTOCOL FOR OTHER ROUTERS** You … Continue reading VPN: DEEP Dive into GRE over IPSec configuration, explanation, and very easy actually once you are familiar with GRE and IPSec!

VPN: DEEP Dive into IPSec, configurations / functions, the VPN fails, but is troubleshot with debugs / verification commands to fix the issue explained!

This is more a Part 2 of 3 in the series of 1 being building a GRE tunnel which we now have, 2 building an IPSec Tunnel which we will have shortly, and 3 placing the GRE traffic into the IPSec VPN for transmission - As IPSec only sends Unicast but GRE takes any type … Continue reading VPN: DEEP Dive into IPSec, configurations / functions, the VPN fails, but is troubleshot with debugs / verification commands to fix the issue explained!

Complete guide to Basic IPSec VPN Configuration, explanations of concepts, debugs, and some show commands for tshooting issues!

Working from Sw1, I want 172.12.23.0 /24 traffic to initialize and be encrypted to the 5.5.5.5 /32 network when traffic hits R2, and vice versa from 5.5.5.5 /32 configured on R1. I want my traffic from this switch specifically destined to network 5.5.5.5 /32 to take the path of R2 - R1 - R5 and … Continue reading Complete guide to Basic IPSec VPN Configuration, explanations of concepts, debugs, and some show commands for tshooting issues!