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 GRE Tunnel configuration over OSPF, explanation of behaviors and how to overcome them!

Now I've spent hours and hours trying to figure GRE out, this was not included in my CCNP ROUTE material except for some DMVPN using mGRE, however I did want to know for practical purposes how to encapsulate broadcast / multicast traffic over an IPSec tunnel which in turn needs a GRE tunnel as there … Continue reading VPN: DEEP Dive into GRE Tunnel configuration over OSPF, explanation of behaviors and how to overcome them!

VPN: DEEP Dive into different VPN Packet Types, Packet Headers, and the differences between VPN Packets and their Modes!

This first image is a break down of the different types of VPN Packet Type by the headers / trailers (or lack thereof), and the following of your typical IPSec VPN Packet Type: The VPN generic representation of the IPSec VPN Packet above works for a general review, but there are details in the headers … Continue reading VPN: DEEP Dive into different VPN Packet Types, Packet Headers, and the differences between VPN Packets and their Modes!