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GRE Tunnel question
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GRE Tunnel question

FAT32FAT32 Administrator, Deal Compiler Extraordinaire
edited August 2018 in Help

This is a very basic question but I am still playing around with tunneling. There are 2 machines: A and B


I have set up a virtual interface that bridged with another interface in machine A. That virtual interface are set up as follow:

auto br1
iface br1 inet static
address 10.0.0.254
netmask 255.255.255.0
bridge_ports none
bridge_stp off
bridge_fd 0
post-up echo 1 > /proc/sys/net/ipv4/ip_forward
post-up iptables -t nat -A POSTROUTING -s '10.0.0.0/24' -o br0 -j MASQUERADE
post-down iptables -t nat -D POSTROUTING -s '10.0.0.0/24' -o br0 -j MASQUERADE
post-up iptables -t nat -A PREROUTING -i br0 -p tcp --dport 1234 -j DNAT --to 10.0.0.100:22
post-down iptables -t nat -D PREROUTING -i br0 -p tcp --dport 1234 -j DNAT --to 10.0.0.100:22


Then, I have also set up a GRE tunnel between machine A and B.

Machine A:

iptunnel add gre1 mode gre local A.A.A.A remote B.B.B.B ttl 255
ip addr add 192.168.0.1/24 dev gre1
ip link set gre1 up

Machine B:

iptunnel add gre1 mode gre local B.B.B.B remote A.A.A.A ttl 255
ip addr add 192.168.0.2/24 dev gre1
ip link set gre1 up


However, I am unable to access Machine B's private network from Machine A using ssh [email protected] -p 1234 however ssh [email protected] -p 1234 works, what is wrong here? Thanks in advance!

Is LET still a community it used to be?

Comments

  • Did you add the usual GRE entries to your sysctl.conf ?
    sysctl -w net.ipv4.conf.all.arp_ignore=3 net.ipv4.conf.all.arp_announce=2
    sysctl -w net.ipv4.conf.all.rp_filter=0
    sysctl -w net.ipv4.conf.gre0.rp_filter=0

    Thanked by 1FAT32
  • FAT32FAT32 Administrator, Deal Compiler Extraordinaire

    @pixievps said:
    Did you add the usual GRE entries to your sysctl.conf ?
    sysctl -w net.ipv4.conf.all.arp_ignore=3 net.ipv4.conf.all.arp_announce=2
    sysctl -w net.ipv4.conf.all.rp_filter=0
    sysctl -w net.ipv4.conf.gre0.rp_filter=0

    Thanks for your comment, just added but still get connection refused

    Is LET still a community it used to be?

  • ClouviderClouvider Member, Provider

    @FAT32 said:

    @pixievps said:
    Did you add the usual GRE entries to your sysctl.conf ?
    sysctl -w net.ipv4.conf.all.arp_ignore=3 net.ipv4.conf.all.arp_announce=2
    sysctl -w net.ipv4.conf.all.rp_filter=0
    sysctl -w net.ipv4.conf.gre0.rp_filter=0

    Thanks for your comment, just added but still get connection refused

    Without reading much, refused or timed out ? That’s a hell of a difference.

    Clouvider Limited - Leading Hosting & Connectivity Partner || Dedicated Server Sale from £39/m - Our Latest LET Offer
    Cloud Web Hosting | SSD & SAS HA OnApp VPS | US, UK, NL & DE Dedicated Servers | Network Services | Colocation | Managed Services

  • FAT32FAT32 Administrator, Deal Compiler Extraordinaire

    @Clouvider said:

    Without reading much, refused or timed out ? That’s a hell of a difference.

    Connection refused

    Is LET still a community it used to be?

  • ClouviderClouvider Member, Provider

    You sure SSH is listening on that IP and that tuere’s No firewall rule preventing it from connecting ? You clearly have connectivity if you can see connection refused.

    Clouvider Limited - Leading Hosting & Connectivity Partner || Dedicated Server Sale from £39/m - Our Latest LET Offer
    Cloud Web Hosting | SSD & SAS HA OnApp VPS | US, UK, NL & DE Dedicated Servers | Network Services | Colocation | Managed Services

  • FAT32FAT32 Administrator, Deal Compiler Extraordinaire
    edited August 2018

    @Clouvider said:
    You sure SSH is listening on that IP and that tuere’s No firewall rule preventing it from connecting ? You clearly have connectivity if you can see connection refused.

    Make sense, I keep looking at my tunneling configuration but it seems it is networking configuration problem.

    eth0 <- Bridge -> br0 <- Bridge -> br1

    br0
    IP: A.A.A.A (Public IP)

    br1
    IP: 10.0.0.254/24

    VM (eth0)
    IP: 10.0.0.100/24
    Gateway: 10.0.0.254

    Port forwarding rule:
    iptables -t nat -A POSTROUTING -s '10.0.0.0/24' -o br0 -j MASQUERADE
    iptables -t nat -A PREROUTING -i br0 -p tcp --dport 1234 -j DNAT --to 10.0.0.100:22


    In machine A, I get connection refused on ssh [email protected] -p 1234, but ssh [email protected] -p 22 works fine

    Is LET still a community it used to be?

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