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I am trying to setup a gre tunnel on debian to receive broadcast packets.

I have the information for an interface

ip address [10.16.2.4 255.255.255.192]
tunnel source [10.16.0.2]
tunnel destination [10.16.254.1]

When I try to create the tunnel with these commands

$ sudo ip tunnel add gre0 mode gre remote 10.16.2.4 local 192.168.1.101 ttl 255
$ sudo ip link set gre0 up

The interface comes up but I do not get any traffic on this tunnel.

How do I properly use ip address, tunnel source and tunnel destination to create the gre tunnel?

chllres
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    "I am trying to setup a gre tunnel on debian to receive broadcast packets." - WHAT ? – drookie Oct 04 '21 at 06:15
  • I am using the linux ip tunnel command; I am unsure where to use the provided ip address/subnet mask, tunnel source and tunnel destination – chllres Oct 04 '21 at 06:17
  • IP tunnels are always point-to-point or /32 (let's leave the point-to-multipoint tunnels out of the scope for now). So the mask is full 32 bits. As for source/destination - those are host addresses, they don't have and don't need a mask. when you open the site in the browser you don't need to know it's IP address mask - all the same here. – drookie Oct 04 '21 at 06:20
  • point to point makes sense, then why would I get an ip address 10.0.5.234 with a mask of 255.255.255.252 wouldn't that be a /30 network? – chllres Oct 04 '21 at 06:31
  • you can use /32 as well. /30 on tunnels will work, but is innacurate. – drookie Oct 04 '21 at 07:22
  • If I create a gre tunnel like; ip tunnel add gre0 mode gre remote [10.16.2.4] local [10.1.0.2] ttl 255 ; ip link set gre0 up ; ip addr add 10.1.0.5 dev gre0 and bring the tunnel up. If I tcpdump there's no traffic going over the tunnel. Also if I try to ping the endpoint, there's also no traffic.. So I am not sure how to proceed. What can I do to debug this further? – chllres Oct 04 '21 at 07:29

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