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

learn more… | top users | synonyms

4
votes
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. ...
2
votes
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 ...
2
votes
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 ...
1
vote
1answer
402 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 ...
1
vote
1answer
755 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 ...
1
vote
1answer
874 views

How to enable debug logging for GRE?

How to enable debug logging for module ip_gre on linux 2.6?
0
votes
1answer
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/...
0
votes
1answer
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 ...
0
votes
1answer
151 views

Load balancing between two (or more) GRE tunnels

I have a hosted service (think zScaler™) 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 ...
0
votes
1answer
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....
0
votes
1answer
136 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 ...
0
votes
1answer
482 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 ...
0
votes
1answer
575 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 ...
0
votes
1answer
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 ...
0
votes
1answer
2k views

Gre Tunnel Cisco Linux traffic forwarding

I setup a gre tunnel a cisco router and a Linux machine, the tunnel interface in the Linux box named pic. Well i have to forward traffic coming from cisco through the Linux box. the rules i've set in ...
1
vote
0answers
36 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 ...
1
vote
0answers
121 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 ...
1
vote
0answers
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. ...
1
vote
0answers
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 ...
1
vote
0answers
44 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 ...
1
vote
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 ...
1
vote
0answers
456 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 23:45:39....
0
votes
0answers
5 views

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 ...
0
votes
0answers
13 views

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 ...
0
votes
0answers
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 ...
0
votes
0answers
22 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. ...
0
votes
0answers
119 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 ...
0
votes
0answers
377 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:...
0
votes
0answers
77 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....
0
votes
0answers
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'...
0
votes
0answers
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 ...
0
votes
0answers
328 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 ...