I have a bunch of IP packets (UDP, ICMP, TCP, SNMP) that I am planning on tunneling from one endpoint to another using a GRE tunnel. Challenge is the tunnel is going to go though a router that only allows TCP traffic, and does check the TCP Established bit on the return.
So, I need to confirm if a GRE tunnel runs over TCP, and would be nice to also know if that checking of the established bit is going to cause me headaches.
Surfed quite a bit on CCO and did not see the data I'm looking for on GRE. If anybody has any thoughts, or knows of any links with the data, I would greatly appreciate it!
GRE is its own protocol that sits right on top of IP, just like UDP and TCP do. It is NOT TCP based. It uses IP protocol number 47. If this router only allows TCP then you're going to run into trouble with GRE. If you need to add an access-list into it, you would do it like:
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...