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

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Changing the gretap tunnel destination address droping the dhcp offer packets

I am having problem setup the L2 over GRE tunnel. create and enable the GRE tunnel: ip link add gre0 type gretap remote (WAG1 IP) local (local ip) ifconfig gre0 up its working fine. Now i ...
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Building a meshed overlay network with outgoing connections going through a gateway

I rent a few Linux servers and the provider doesn't offer a VLAN. Each server gets a public IPv4 address, which are not part of the same subnet. I would like to create a network which "hides" the ...
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23 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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28 views

multi gre tunnels to one IP

I have an issue with GRE tunnels after connecting multi-GRE tunnels with different IP's to the server, using this tutorial: http://wiki.buyvm.net/doku.php/gre_tunnel every GRE tunnel has interface ...
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71 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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12 views

DNS with GRE Tunnel [duplicate]

I'm in a big issue here to make it work I'm already at least about 60% done, but it is difficult and I would like to count on the help guys here who may have already done this type of configuration. ...
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23 views

DNS using GRE work 50%

l'm in a big issue here to make it work I'm already at least about 60% done, but it is difficult and I would like to count on the help guys here who may have already done this type of configuration. ...
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110 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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37 views

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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155 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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122 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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41 views

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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134 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....
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54 views

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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1answer
60 views

GRE - overlay network

I am renting a set of dedicated servers, and they only have a single interface to internet. However, for a lot of use cases, I would like my servers to communicate through a private IP network. For ...
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45 views

IP Tables forwarding tun0 over gre1 (OpenVPN)

I haven't found a very descriptive thread (and sorry if there is one in existence - in my several hours of searching I've found nothing to my specific situation). My main issue here is getting my ...
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120 views

TCP Out-of-order packets over GRE causing disconnect

I'm experiencing an issue with a small percentage of TCP connections over a GRE tunnel between two servers. The topology is basically Internet <-> GRE Tunnel <-> Backend The GRE tunnel and the ...
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158 views

Iptables not routing GRE protocol

First things first, there might be a few English errors, considering it's not my native language. I'm having a problem with VPN(GRE protocol) passing through Iptables. I've done this at least a dozen ...
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380 views

Strongswan IPsec: routing arbitrary subnets over /32 IPsec endpoints

I have a basic setup between two sites A (FreeBSD, 10.0.0.1/24 nat'd to 1.1.1.1), B (Linux, 2.2.2.2), with only A behind NAT. I've only been able to get it working in tunnel mode. Here's my ipsec.conf:...
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78 views

Openbsd set connect on PPTP server behind packet filter

I have firewall on OpenBSD use Packet Filter and behind him MS Windows server with PPTP server. I need allow connect this PPTP server from internet. I set in OpenBSD: net.inet.gre.allow=1 net.inet....
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1answer
182 views

Poor IPsec over GRE performances

I have set up an IPsec over GRE connection with a remote host, both are NetBSD 6.1 based. The "client" is connected to the Internet through a 400Mbps fiber connection. The "server" is located on a ...
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296 views

https connection can't established behind a gre tunnel

I have a network topological graph like this: Local box GateWay box +---------------+ +--------------------------+ |192.168.1.200 | -> |192.168.1.2 10.2.10.2 | +-------...
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137 views

Set up transparent GRE/VPN to redirect all traffic to an External datacenter

I need to setup an existing server with multiple IPs (from OVH) to send all the traffic (through VPN or GRE tunnel) to an external server that has only 1 Public IP. I want to make it like every local ...
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2answers
2k views

How to route outbound traffic for a particular destination IP address to GRE Tunnel in CentOS?

Hello I am trying to configure a network like this network diagram :- Well I have to create a GRE Tunnel at my alpha server and route some particular traffic to GRE Tunnel.I want to do the configs ...
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75 views

GRE Tunnel Collapsing in One Direction

This is a related question to another thread I posted. I'm having an issue where my GRE tunnel is collapsing in one direction, but can be reopened by ping the other server using the GRE Interface. I'...
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1answer
665 views

Multicraft: Port Forwarding through a GRE Tunnel

For the past week I've been attempting to protect a server from DOS attacks by utilizing a GRE tunnel from a VPS to a dedicated machine without much success. Visual: User --> VPS --> Dedicated ...
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95 views

Public IP not responding because routing table…?

Fixed with: /etc/iproute2/rt_tables 1 tble_eth0 /etc/sysconfig/network-scripts/route-eth0 104.000.64.0/18 dev eth0 src 104.000.65.38 table tble_eth0 default via 104.000.64.1 dev eth0 src 104.000.65....
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1answer
281 views

Remote end of IPSec transport is 'permenantly glued' to loopback after some messing around with GRE

So, I have managed to get IPSec transport over ESP between two hosts using racoon: the 'local' host, 1.1.1.1, and the remote, 2.2.2.2. It only worked for ICMP (other traffic ignored the SA), but that'...
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486 views

TLS-intolerant sites suddenly not working

About 2 weeks ago users started reporting that they were unable to access two https-only sites. When I inspected these sites I found they were completely intolerant to TLS. In order to connect, SSL3 ...
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1answer
577 views

GRE Tunnel in CentOS

How to create a GRE Tunnel in CentOS pointing all connections to server A for the server B? I have a public server with DDoS protection and need to use this as a firewall to filter acess to the other ...
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403 views

Using my IPs on OVH server via GRE

I can't route my IPs into a OVH server, can you help me to find the problem? Mikrotik GRE IP: 192.168.55.10 OVH Server GRE IP: 192.168.55.20 GRE iface name: ali1_fr1-ovz1 IP to route from Mikrotik to ...
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128 views

Listening “through” GRE Tunnel

Currently I'm looking to learn about using GRE Tunnels and I have the following scheme: Server1 (200.1.2.3) ----> Server2 (190.1.2.3) Both servers have public IPs Then I've setup a GRE Tunnel with ...
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1k views

WCCP and Squid, and Tunnels

I'm trying to configure WCCP + Squid with the following documentation: http://www.crypt.gen.nz/papers/cisco_squid_wccp.html I have a cisco switch, a test client, and a squid proxy server. I think ...
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238 views

How is my GRE-Tunneled packet being routed? [closed]

I'm trying to figure out exactly what is happening when I create a GRE tunnel. My network looks like this (-> means directly connected): Computer A (eth0: 10.0.1.1) -> (eth0: 10.0.1.2) Router B (...
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7k views

Transparent Ethernet over GRE not forwarding traffic

I am running on Linux 2.6.30.9 and have been trying to setup a transparent ethernet over GRE tunnel. The network topology used is as follows: I want to bridge PC1 and PC2 using Transparent Ethernet ...
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2k views

IP/GRE compiled in kernel but gre0 interface doesnt exist

Im trying to create IP over GRE tunnel but i get No such device: ip tunnel add gre0 mode gre remote 192.168.152.22 local 192.168.152.21 ttl 255 ioctl: No such device I have compiled GRE support in ...
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1k views

DMVPN and OSPF (two tunnels dynamic routing)

please help me to resolve the problem with routing between dmvpn GRE tunnels. I've got a DMVPN HUB and SPOKE topology. HUB has public ip address in internet. SPOKE has two ISPs for redundancy. I've ...
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329 views

Using public interfaces on a server connected through a GRE tunnel

I'm pretty new to networking so please forgive any terminology mistakes. I have 2 servers connected with a GRE tunnel. Server1 (10.0.0.1) ----> Server2 (10.0.0.2) I want to be able to bind to the ...
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2k views

GRE keepalive with Linux and RouterOS

I have a Linux host and couple of routerboadrs. I created a GRE tunnel, but Linux does not answer keepalive packages. Then router mark gre connection as unreachable, so I cant send to Linux host from ...
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72 views

GRE tunnel / Route traffic based on which domain the user is trying to access

Imagine this kind of setup. 5 servers. 1 server will be the "front-end", all the traffic has to go through it first before going to the 4 other servers. I don't want people to know the IPs of the ...
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4k views

GRE: read from PTY failed error when connecting multiple clients to PPTP

I have just installed a pptp server and now I can make it work. The problem is, it can only be connected to by one client. How do I set it up so that it will allow multiple users? Here is the error ...
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1answer
931 views

How GRE traffic finds way after arrive GRE remote end points (in open vswitch)?

I'm quite new to both network and open vswitch, I'm not sure whether this question is more relevant to open vswitch(ovs) or gre. belows are ovs settint commands. There are two hosts. Each host has ...
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392 views

GRE tunneling in vmware vsphere guest [closed]

Is it possible to make a GRE tunnel between a dedicated linux machine and a vmware vsphere guest VM (running debian wheezy)?
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759 views

Ubuntu GRE local ip address, wan ip of router, or ip of ubuntu server

I have an ubuntu server behind a router that I am configuring to have a GRE tunnel to another remote device across the interwebs. in the config, I add the line: pre-up iptunnel add tun1 mode gre ...
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1k views

openvswitch: connecting two virtual private networks on two different machines with gre/ipsec

Here is the setup: We have a hardware (server) that presents a service to the customer (or "outside world", if you so will). Internally, the services and functions are distributed over several virtual ...
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716 views

How to troubleshoot GRE tunnel issues?

I commonly run into issues where a GRE tunnel (CentOS server to server, not router based) works and pings fine from both ends but the IP / Range being tunneled does not function. This almost always ...
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408 views

How to check for GRE Tunnels [closed]

Is there a way to check for GRE Tunnels? I've heard spammers will use GRE tunnels to send mail from a central machine out of another and would like to check for possible GRE tunnels.
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1k views

Why two addresses in configuring a GRE tunnel?

As I can find in this support document, in order to configure a GRE tunnel between two routers R1 and R2, I issue the following sets of commands (mtu and mss omitted), R1 R1(config)# interface ...
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1answer
609 views

Redirect SSH traffic through GRE tunnel

I'm trying to redirect all local connections with destination matchs port 22 to specified tunnel using iptables MARK, but, something is going wrong. 1.1.1.1 my public address 2.2.2.2 tunnel public ...
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1answer
3k views

How to force certain traffic through GRE tunnel?

Here's what I do. Server (public internet is 222.x.x.x): echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf sysctl -p iptunnel add gre1 mode gre local 222.x.x.x remote 115.x.x.x ttl 255 ...