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

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Cannot Delete GRE Tunnel

I am configuring a GRE tunnel in Linux 2.6.26 and I've been facing a very strange problem for which I could not find any solution. I have created a GRE tunnel called gre0, but no matter what I do, I ...
4
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1answer
10k views

PPTP connection fails with errors 800/806

I've got a client (Server 2008 R2) that won't connect to our production environment PPTP VPN server (Server 2003, running RRAS). The server is behind a firewall that has TCP1723 open as well as GRE. ...
3
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1answer
837 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 ...
3
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1answer
4k views

Multiple GRE tunnels on the same host, only one routes incoming packets

I'm having a routing problem on CentOS 6.2 (kernel 2.6.32-220) Here's the setup: One host is on my local network. It's talking to two nearly identical hosts at a remote location. The two remote ...
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4answers
9k views

How to setup an IPSec / GRE tunnel on Windows Server 2008

I have a Windows Server 2008 that has a single network interface configured with a public IP address. My business partner has a private network. From my server, I need to access all the devices on his ...
2
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1answer
178 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 ...
2
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1answer
596 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 ...
2
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1answer
256 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 ...
2
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1answer
591 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 ...
2
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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 ...
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2answers
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Is it possible to find out the make/model of the router remotely?

First a little background. My company is renting some servers at the Terremark cloud. As we want to connect our servers to the infrastructure of a mobile carrier in order to restrict our end users to ...
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1answer
3k views

What's the difference between GRE and IPIP tunnel?

And which one is better for connecting two linux machines?
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2answers
4k views

GRE Tunnel over IPsec with Loopback

I'm having a really hard time trying to estabilish a VPN connection using a GRE over IPsec tunnel. The problem is that it involves some sort of "loopback" connection which I don't understand -- let ...
1
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1answer
72 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 ...
1
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1answer
50 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 ...
1
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1answer
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 ...
1
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1answer
366 views

How to forward all GRE traffic to a particular network interface?

I want to forward all GRE traffic (IP protocol 47) coming on eth2 to br0 on my machine. How can I do that?
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1answer
2k views

GRE Tunnel between Linux server and XP client

I want to set up a simple unencrypted tunnel between a linux-server (running SLES9) and a client (running XP SP3). The reason for this is that there are many network devices in between and the client ...
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0answers
33 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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0answers
90 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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0answers
31 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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0answers
43 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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0answers
41 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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0answers
362 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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1answer
669 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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1answer
1k views

Linux/Vyatta failover with GRE and OSPF/BGP

I have strange problem with routing failover in scenario: I'm trying do this failover via ospf or bgp, in both happens the same strange behavior with tunnels: For 192.7.0.0 TUN providing default route ...
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0answers
1k views

OpenNHRP configuration without IPsec

I'm attempting to use OpenNHRP on a linux box to connect with a Cisco Router. I want to allow GRE tunnels from the linux box to the Cisco router dynamically, but I'm not implementing DMVPN on the ...
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0answers
18 views

Setting up a GRE tunnel on a Cisco ASA 5505 [duplicate]

Possible Duplicate: Set up a GRE tunnel with Cisco PIX-506 v6.3 I'm trying to establish one half of a GRE tunnel, the other being configured by my service provider. I have a Cisco ASA 5505 ...
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1answer
606 views

how to forward all traffic over a GRE over IPsec VPN on cisco routers?

i have 2 cisco ISR 2821 and 2811 and they are connected over a site to site GRE over IPsec vpn. my question is that, how can i forward all traffic or web traffic to the other router? thanks
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445 views

GRE debug: “adding 0 encap bytes”?

What this debug message actually means? Shouldn't encapsulation add 24 extra bytes or not? For what reason encapsulation is not adding bytes to original packet in this debug message? Dec 28 ...
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1answer
847 views

How to enable debug logging for GRE?

How to enable debug logging for module ip_gre on linux 2.6?
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2answers
780 views

Multiple GRE NAT router

Does there exist a router that supports multiple GRE connections over NAT? Im currently running pfSense, and it only supports 1 at a time. I understand why, its just a drag as there are multiple ...
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2answers
501 views

Set up a GRE tunnel with Cisco PIX-506 v6.3

I'm trying to establish one half of a GRE tunnel, the other being configured by my service provider. I have a Cisco PIX-506-E running Firewall version 6.3(5). Provider Router Public IP: 8.8.8.8 My ...
0
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1answer
369 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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2answers
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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
91 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 ...
0
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1answer
3k 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 ...
0
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1answer
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 ...
0
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1answer
229 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 ...
0
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1answer
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 ...
0
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2answers
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 ...
0
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1answer
2k views

using a gre tunnel as default route

I have two private networks (A, B) that connects via another company's private network (C). Network A has internet access. I want to make a tunnel between B and A that goes through C. Then network B ...
0
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1answer
187 views

GRE Encapsulation and Multicast

How does GRE Encapsulation actually send multicast traffic? My CISCO textbook tells me that the multicast packet is carried inside a unicast packet. My understanding is: Multicast packet, say for ...
0
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1answer
2k views

Routing subnet over GRE tunnel

Im trying to configure a GRE over IPSec connection between two subnets. The IPSec tunnel is opened and now I want to add a GRE tunnel over it: ip tunnel add GRE01 mode gre remote 10.244.0.1 local ...
0
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3answers
406 views

Does a router have to explicitly support GRE in order to pass those connections?

I have replaced a mess of Cisco routers with a single Dell PowerConnect 6224. These routers serve (and served) public IPs to clients, and just acted as routers to the upstream provider. Prior to the ...
0
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1answer
749 views

GRE over IPSec behind FW

I have a checkpoint S-Box which is a gateway for network 192.168.0.0/24. Internal IP is 192.168.0.1. On the S-Box configured static VPN tunnel with local IP 10.x.x.x and remote 10.y.y.y. I need to ...
0
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1answer
9 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 ...
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0answers
25 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 ...
0
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1answer
49 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 ...
0
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0answers
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. ...