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Old 06-04-2012, 01:05 PM   #1
seccentral
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Registered: Mar 2011
Distribution: Linux mint
Posts: 21

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linux gre nat problem with traffic forwarding


[home net] -> (eth0)[centos router](eth1) -> [isp] -> office

home-net: 192.168.0.0/24
isp network: 10.11.0.0/24

office net: 10.11.221.0/24

the centos router does nat for my home pcs and i wanted a nice gre tunnel to the office, so i ssh into both centos and office router, setup tun interfaces, assign ip addresses etc, ping test, both hosts(centos router and office router) can ping each other's gre tun interfaces.
my router's gre endpoint ip address is 10.0.0.1
office router's gre endpoint ip addr is 10.0.0.2

however, when i try to ping hosts at the office from within my [home net] i get timeouts, but if i try to ping the local gre endpoint it works.
example:
user@192.168.0.100 : ping 10.11.221.5 -> times out. >
user@192.168.0.100 : ping 10.0.0.1 -> works \m/
user@192.168.0.100 : ping 10.0.0.2 -> phails

i'm not sure i understand why my centos box doesn't forward packets from my home net through the gre and back again.

err... yes, isp does natting and i do natting too. so home boxes are behind 2 nats but i dont care.

PS: i can't add a 'gre' tag to this thread lol

Last edited by seccentral; 06-04-2012 at 01:06 PM.
 
Old 06-04-2012, 11:40 PM   #2
Lexus45
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Registered: Jan 2010
Location: Kurgan, Russia
Distribution: Slackware, Ubuntu
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try to load the 'nf_conntrack_pptp' and 'nf_conntrack_proto_gre' module. maybe 'nf_nat_proto_gre'
Inspect all available gre and pptp modules with 'modprobe -l | grep pptp' anf 'modprobe -l | grep gre'
 
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Old 06-06-2012, 02:04 AM   #3
seccentral
LQ Newbie
 
Registered: Mar 2011
Distribution: Linux mint
Posts: 21

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Quote:
[root@x-router ~]# modprobe -l | grep gre
kernel/drivers/media/rc/keymaps/rc-pinnacle-grey.ko
kernel/net/sched/sch_gred.ko
kernel/net/sched/sch_ingress.ko
kernel/net/netfilter/nf_conntrack_proto_gre.ko
kernel/net/ipv4/netfilter/nf_nat_proto_gre.ko
kernel/net/ipv4/ip_gre.ko
and

Quote:
[root@x-router ~]# modprobe -l | grep pptp
kernel/net/netfilter/nf_conntrack_pptp.ko
kernel/net/ipv4/netfilter/nf_nat_pptp.ko

and on the remote office box:
Quote:
[root@thor ~]# modprobe -l | grep gre
/lib/modules/2.6.31.1-ddnet-v0.3/kernel/net/ipv4/ip_gre.ko
/lib/modules/2.6.31.1-ddnet-v0.3/kernel/net/netfilter/nf_conntrack_proto_gre.ko
/lib/modules/2.6.31.1-ddnet-v0.3/kernel/net/ipv4/netfilter/nf_nat_proto_gre.ko
/lib/modules/2.6.31.1-ddnet-v0.3/kernel/net/sched/sch_gred.ko
/lib/modules/2.6.31.1-ddnet-v0.3/kernel/net/sched/sch_ingress.ko
[root@thor ~]# modprobe -l | grep pptp
/lib/modules/2.6.31.1-ddnet-v0.3/kernel/net/netfilter/nf_conntrack_pptp.ko
/lib/modules/2.6.31.1-ddnet-v0.3/kernel/net/ipv4/netfilter/nf_nat_pptp.ko
still no luck :/

Last edited by seccentral; 06-06-2012 at 02:06 AM.
 
Old 06-06-2012, 02:09 AM   #4
seccentral
LQ Newbie
 
Registered: Mar 2011
Distribution: Linux mint
Posts: 21

Original Poster
Rep: Reputation: 0
oh lord, i had routes to the office internal network set up on my home nat box, but i forgot to put routes to my internal home network on the remote office router box.
now that i've placed them it's all good.

thanks for the module tip tho, it helped.
 
  


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