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Questions tagged [gre]

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

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

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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 machines (of different roles). We use kvm for…
lImbus
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How to check for GRE Tunnels

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.
Tiffany Walker
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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 Tunnel1 R1(config-if)# ip address 172.16.1.1…
Masroor
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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 will use A as default route for internet…
Sirber
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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 PIX Public IP: 7.7.7.7 Provider Tunnel Address:…
Antonius Bloch
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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 RIP, has address 224.0.0.9. GRE takes that, wraps it…
Edgar Velasquez Lim
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cannot ping through gre tunnel

This question has been merged I have 4 machines machine 1 have ip address 172.13.0.40/24 machine 2 have two ip address 172.13.0.1/24 and 172.12.0.1/24 machine 3 have two ip address 172.12.0.50/24 and 172.17.0.1/24 machine 4 have ip address…
sanketmlad
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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 10.244.245.32 ttl 255 ip link set GRE01 up ip addr…
eMgz
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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 replacement, a customer had a VPN appliance that…
David Mackintosh
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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 create a GRE tunnel with local 10.z.z.z and remote…
Boris
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GRE tunnel doesn't forward connection from proxy to server

I'm trying to setup a GRE tunnel for an anti-dos solution for my Minecraft hosting. Server A is the server which forwards the connections to the backend server. Server B is the backend server. Whenever I connect to a normal Minecraft server on…
sidboy55555
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Connection Refused (GRE Tunnel - FiveM)

I am running a game server using Vultr. What I am trying to do is run the game server (backend server) through a GRE Tunnel. For this, I am using x4b.net for my GRE Tunnel. A few things to note: The guide that I used is listed here:…
Andromeda
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Force UDP traffic to exit through the GRE Tunnel

I have an application that suffers from ddos. So we put it behind a filter that works on the basis of GRE. The filter works fine, but the application has a subapplication that answers to other ports and ends up answering to a different IP as well…
Joabe Meirelles
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GRE tunnel. Port Forwarding with IPTables from VPS to Local Server not working

Dear ServerFault community, I have an OVH VPS with 3 public IPs (1.1.1.1, 2.2.2.2, 3.3.3.3) and I am trying to forward them individually, with one tunnel for each IP, to a server in my office (IP 5.5.5.5) with port forwarding. This so that I can…
Nicolò
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GRE set outbound IP route

Node A Public IP: 198.244.xxx.151 Node B Public IP: 37.59.xxx.234 Node A: sudo ip tunnel add gre1 mode gre local 198.244.xxx.151 remote 37.59.xxx.234 ttl 255 sudo ip addr add 10.0.0.1/30 dev gre1 sudo ip link set gre1 up iptables -t nat -A…
Toodarday
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