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Generic Routing Encapsulation (GRE) is a tunneling protocol, developed by Cisco.

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Tunnel Linux traffic to Windows

I have two servers. Windows and Linux. Let's say Linux has the IP 1.2.3.4 and Windows 5.6.7.8. I want all traffic to be forwarded to windows as a tunnel. If I connect with 1.2.3.4:329 I want to ...
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incomming connection from GRE tunnel is always in SYN_RECV state

I create a GRE tunnel according to this tutorial : https://community.hetzner.com/tutorials/linux-setup-gre-tunnel/ in base server (server A in tutorial ) i have BGP advertise . when i enable the ...
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Forwarding Home Game-Server through GRE Tunnel | Can't ping remote GRE IPs

I am having trouble routing my game-servers through GRE. I do not receive a ping from either side when pinging them. I can ping the local GRE interface; however, I cannot ping the remote GRE interface....
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Cannot ping remote host across GRE tunnel over IPSec

I need to setup a GRE tunnel over IPSec to support multicast and, at the same time, encrypt my communication. I managed to setup the IPSec tunnel (strongswan) in EC2. I can ping the remote host and I ...
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Packets not getting forwarded on Centos7 between GRE tunnels

I'm have configured GRE tunnels between centos machines and corresponding routing tables on individual centos machines as shown in the image: I dont have enough reputation to post images Router1-----...
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Interface bonding on GRE tunnel with nmcli

I have two Ubuntu server-based routers and I'd like to bond (in broadcast mode, since I only care about redundancy) a radio link (where the radio equipment is connected to an Ethernet port) and a LTE ...
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40 views

gretap tunnel return traffic not being handled

I'm using iproute2 to add a GRE layer 2 tunnel with a vlan tag as shown below. ip link add name gre1 type gretap local 10.0.0.2 remote 8.8.8.8 ip link add name gre1.100 link gre1 type vlan proto 802....
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127 views

How to route server_A's internet traffic through server_B using a GRE Tunnel?

I have two Linux servers. I want to use a GRE tunnel to route all internet traffic from ClientBox through a tunnel to GatewayBox, so that, to the rest of the internet, my ClientBox appears to be ...
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105 views

Multiple virtual interfaces on top of GRE tunnel

I have a GRE tunnel defined on an interface: $ ip tunnel add ap2gre mode gre remote 10.1.0.1 local 192.168.1.2 ttl 255 $ ip tunnel ap2gre: gre/ip remote 10.1.0.1 local 192.168.1.2 ttl 255 $ ip ...
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ACK packet lost in GRE tunnel for IPv6 in IPv4

At home (79.1.1.156), my ISP doesnā€™t provide IPv6 so Iā€™m connecting my server to an external server (95.1.1.126) that has IPv6 access via a GRE tunnel, with this simple setup: ip tunnel add gretun ...
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Seperate GRE tunnels cannot ping eachother

I have two systems that both tunnel to a core routing server. These systems both have a client address from the same /64 IPv6 prefix. From each client, I can ping the server with no problems and vice ...
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GRE Tunnel Dies in 1 direction

I have built a GRE tunnel over tap0 interface between 2 Centos-7 hosts. I've done this via the following: Host-A: 10.0.10.5 Host-B: 10.0.20.5 On host A: ip tunnel add tap0 mode gre remote 10.0.20....
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How to generate a Cisco GRE keepalive request from an Ubuntu machine

I need to generate a GRE Keepalive packet from a plain ubuntu machine. Ubuntu1-----------------------Ubuntu2 I configure GRE tunnel as below on UBuntu1 ip tunnel add gre1 mode gre remote x.x.x.x ...
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321 views

Route incoming traffic through GRE tunnel

So I have a VPS and Dedi server both running Debian 9.9. 139.99.x.x: VPS 139.89.x.x: DEDI The Dedi server runs a game server but can't be directly accessible, I want to route all traffic through my ...
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GRE traffic not forwarded to local subnet

I have two debian machines in difference locations and want to enable routing between the two internal subnets via GRE. My general routing is already working, meaning any internal machine directs ...
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714 views

Using iptables NAT to forward GRE tunnel

I have two hosts which need to have a GRE tunnel between them. In between the two I have a relay host which needs to perform NAT and forward the GRE traffic in either direction. grehostA --- ...
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3answers
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Allow GRE (IP protocol 47) over Linux router NAT for a subnet

I have network setup as shown below: The VPN server running is windows 2012 server default VPN, which uses GRE protocol. I am able to have VPN connection to that remote vpn server, from my intranet ...
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1answer
253 views

ERSPAN to IP on Centos host with multi interfaces on the same subnet

I have an interesting configuration and would like some help getting it to work. On a hardware network monitoring probe, i have 2 physical interfaces. mgmt is the management interface and mon1 is a ...
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377 views

Linux GRE Tunnel: Remote Address parameter

The Linux GRE tunnel as two parameters, local address and remote address. Suppose I have two routers, the left one is outside of a NAT and right one is inside NAT, then I want to create a GRE tunnel ...
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176 views

GRE perfomance issue on Linux

I got a strange GRE perfomance issue. The setup is shown bellow. [host1] --- GRE over Eth 1G --- [linux router] --- Eth 10G --- [host2] Iperf transfer rate host1>host2 reaches 950Mbps. It encreases ...
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333 views

tc qdisc with GRE in openwrt

I'm trying to implement traffic control to GRE interface in an openwrt board. For this i followed below steps, Create GRE interface named gre1 in both tunnel end devices. Tested reachability with ...
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1answer
748 views

How to setup a GRE 3 host mesh without loops and forwards with OpenVSwitch?

I'm setting up a quite simple 3 host Proxmox (Debian) HA cluster. All VMs should be in the same subnet and when one fails over to another host inside the VM no reconfiguration should be required and ...
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Packet loss in IpSec/GRE tunnel

This is my setup: +--------------------+ +-------------------+ +--------------------+ | Router B a +-----+ Router+Firewall C | | b Router D | | 10.10.10.1 -----------...
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GRE Tunneling not working

i've been looking everywhere for a solution to this but have found really nothing. I was wondering if it is possible to forward ports such as 80 through an OpenVPN connection? I am using an OVH VPS ...
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1answer
1k views

Get IP over DHCP for GRE-tunnel

I need to create a GRE tunnel from a client to a server. This is my setup. Setup: ________________________________ _________________________________ ______________________________ |Server ...
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1answer
1k views

Bonding over OpenVPN, for fault tolerance

I have two OpenVPN server, and two machines connecting to them. Server 1 openvpn address: 10.158.1.1 Server 2 openvpn address: 10.158.2.1 Machine 1 has address 10.158.1.11 on server 1, 10.158.2.11 ...
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1answer
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iptables SNAT not working for GRE packets

I am trying to apply SNAT to a PPTP client. The TCP/1723 packets are being SNATed properly but not the GRE ones. Can anyone spot what's wrong? I have the following iptables configuration: $ sudo ...
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1answer
230 views

Public to Public IP GRE

I've managed to setup a GRE tunnel between two servers using BuyVM's very great guide (also used a guide via ServerFault) It simply works. I can ping internally So. To get into perspective: A = 1.1....
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451 views

Nat over GRE using IPsec VPN tunnel

Iā€™m working on implementing VPN tunnel IPSec GRE from Natted Linux box with Ubuntu. I have found a very useful article, related to IPSec-GRE tunnel behind NAT, made with Cisco routers. I have ...
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1answer
713 views

L2TPv3 tunnel private IPs not working

I'm trying to setup L2TPv3 tunnel between 2 servers - CentOS 7 and Ubuntu 16 On CentOS 7 end I have the following: ip l2tp add tunnel tunnel_id 6000 peer_tunnel_id 5000 encap udp local LOCAL_IP ...
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2k views

IPSEC over GRE tunnel on PFSENSE

I have two PFsense routers xxx.xxx.xxx.28 and xxx.xxx.xxx.27 and local networks behind them 192.168.110.0/24 and 192.168.111.0/24. The point is to set up GRE tunnel with IPSEC between these networks. ...
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1answer
308 views

GRE With scaleway

i'm having some problem here to create a GRE tunneling, it' theoretically simple, i have 2 clouds, one, with DDoS Protection, and another, without that. In my first cloud, it have DDoS, hosted in OVH, ...
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1answer
4k views

PPTP Passthrough Centos 7/Firewalld router to Windows Server

I have a Centos 7 server running firewalld to allow public services to access internal services on a separate VLAN (dual NICs). I imported a Windows VM but I do not know what rules I need to put in ...
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1answer
590 views

Virtualize using IPs under GRE Tunnel (or NAT?)

Well, this is the situation I am experiencing: I've got a dedicated server from OVH, and a dedicated server from another company, since the maximum RAM for the OVH server (GAME category) is 64Gb of ...
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675 views

Proxmox NAT with GRE tunnel as outside interface

End goal (ASCII Diagram) WAN->Router->Server->GRE Tunnel->VM network->VM #1, etc. I should explain some things first. I have a server running Proxmox (Debian 8.7 x64). It's ...
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1answer
2k views

GRE tunnel TTL number

Here is the setting on server A: iface serverA_gre0 inet tunnel address 172.24.0.85 mode gre endpoint x.x.x.x dstaddr 172.24.0.86 netmask 255.255.255.252 ...
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196 views

Is there a load balancer that will terminate a GRE tunnel?

I have a network in which several site routers send portions of their traffic to an inspection device via GRE tunnel. I am beginning to exceed the capacity of the inspection device. I could always ...
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1answer
259 views

Why am i receiving so many unsolicited GRE packets?

My (linux) server has some fairly simple iptables rules. iptables -A INPUT -p icmp -j ACCEPT iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT iptables -A INPUT -m tcp -p tcp --dport ssh -j ...
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368 views

Gre tunnel routing Public IPs between two servers

I want to route public IPs from server A and use them on server B. I created the GRE tunnel and it works. I then setup a route on server A in the following way: (public IP not actual IP) 192.168.11....
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1answer
3k views

MikroTik GRE over IPSec

I'm trying to establish a GRE over IPSec tunnel between two MikroTik devices. Everything seems to work yet when I sniff the WAN interface I can clearly see the GRE packets which theoretically I ...
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1answer
375 views

pptp gre in csf firewall

i have a senior problem. when i want to connecting a pptp over a tap adaptor or a pptp connection have get disconnected and get this errors on messages logs: linux pptpd[20275]: GRE: read(fd=7,buffer=...
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486 views

GRE protocol type for Ethernet over GRE?

For a IP over GRE tunnel, as defined by the RFC 2784, the "protocol" field is filled with 0x0800 (defined as ETH_P_IP in the Linux kernel according to this source http://www.scs.stanford.edu/histar/...
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1answer
1k views

Reverse proxy for DoS / DDoS protection

after i search how to protect my website host server using GRE tunnels, some friends of this forum give me a tip to use Reverse Proxy that would be better. But i don't found any guide on how to ...
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1answer
915 views

Linux GRE keep alive

What are possibilities in Linux kernel (?) to work with Cisco endpoint encorporating GRE keep-alives? We have GRE IPsec tunnel set up with another company. We would like to have backup tunnel which ...
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What could cause racoonctl to show a Phase2 count higher than the number of ports racoon is listening on?

In my setup I have some EC2 instances in different regions linked by GRE tunnels, using ISAKMP via racoon. This setup is inherited, so bear with me if I fumble with terminology. Sometimes I get weird ...
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1answer
1k views

Load balancing between two (or more) GRE tunnels

I have a hosted service (think zScalerā„¢) that is having me send my traffic to it via GRE tunnels. I am given two appliances and want to load balance my traffic between the two tunnels. I could ...
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917 views

Ethernet over GRE bridging - Proxmox

I'm trying to install two proxmox on Online.net server's, and I just realized that their RPN feature doesn't work at all like the OVH vRacks. Since I need the different VM's on both hypervisors to be ...
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Cisco 1941 EIGRP UP DOWN

We have two cisco routers 1841 and 1941. The 1841 keeps generating "holding time expired" and "interface goodbye recieved" about its neighbor the 1941. The VPN IPSec protocol seems to stay up. ...
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1k views

Amazon Linux - iptables NAT rules not matching GRE traffic

I'm trying to prototype something in AWS VPC/EC2, but I can't get my NAT rules to work. I have the following setup (all instances running the Amazon Linux AMI): GRE Tunnel between instances 10.0.0.10 ...
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internet access for system over multiple hops of ipsec using GRE and OSPF

I have the following setup: linux client @ 172.16.10.68 linux gateway @ 172.16.10.69, ipsec tunnel to aws box #1, gre tunnel 10.254.0.0/30 aws box #1, ipsec tunnel from linux gw, ipsec tunnel to ...

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