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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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Question about gre tunnels (lemmy.goblackcat.com)

submitted 1 year ago by [email protected] to c/[email protected]

3 comments fedilink hide all child comments

Hello, I have a rather complicated need to use a gre tunnel and I am having difficulty getting it working. The tunnel is between my home server and Oracle VM. Below is a picture of the topology with config.

Pings between the home server and Oracle VM over the gre tunnel do not seem to be going through as evidenced by tcpdump. I do notice however that the firewall has the correct state table showing that address translation. I am certain that both machines' firewalls are not dropping packets because iptables is not showing anything dropped. I am at a loss here so I welcome any ideas.

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[–] [email protected] 6 points 1 year ago (1 children)

I’m unable to read the text I’m the image, can you post your firewall rules?

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

I believe OP has made some mistakes when pasting the text

[Diagram]
Oracle VM: Linux
External IP: 192.0.2.1
Internal IP: 172.16.0.2
 |
 | GRE Tunnel
 v
Home Server: Linux
Internal IP: 172.16.0.2
 |
 |
 v
Firewall: FreeBSD
Internal IP: 172.16.0.1
External IP: 192.0.2.2

[Text]
Home Linux Server GRE config:
$ sudo ip tunnel add gre0 mode gre remote 172.16.0.2 local 192.0.2.1 ttl 255
$ sudo ip link set gre0 up
$ sudo ip addr add 10.100.10.1/24 dev gre0


Home Linux Server GRE config:
$ sudo ip tunnel add gre0 mode gre remote 192.0.2.2 local 192.0.2.1 ttl 255
$ sudo ip link set gre0 up
$ sudo ip addr add 10.100.10.1/24 dev gre0

Firewall:
nat on igb1 inet from ! (igb1) to any -> (igb1:0)
nat on igb0 inet proto gre from 172.16.0.2 to any -> (igb1:0)
rdr pass on igb1 inet proto gre from 141.148.84.178 to (igb1) -> 172.16.0.2

[–] [email protected] 1 points 1 year ago

gre implies you want to run dynamic routing over the tunnel but no routing is configured? If you don't need dynamic routing (why would you on a P2P tunnel?) but do want privacy then use IPsec or SSH instead?