Re: openvpn to ipsec routing question
Christoph Leser wrote: Hello, the question is about how to route traffic from an openvpn tunnel to an ipsec tunnel. This is my setup: The OpenBSD gateway has an internal (10.0.1.1/24 ) and external (x.x.x.x/30) interface. The internal net is NAT'ed to the external interface to provide internet access to hosts on the internal net. Through the external interface an ipsec SA ( security association ) is established ( tunnel mode ) between my internal net ( 10.0.1/24 ) and another local net of a remote site ( 10.0.2/24 ). So hosts on the internal net can reach hosts on the internet (being NAT'ed ) as well as hosts on the remote private net 10.0.2/24 ( not being NAT'ed ). Now I have setup an openvpn server on this box. This openvpn server gives out addresses from yet another net ( 10.0.3/24 ) to the connected clients. Connections from openvpn clients are NAT'Ed to the internal interface to make them appear as being directly attached to the local private net ( 10.0.1/24 ). So far, it works. Now I want the clients on the openvpn subnet ( 10.0.3/24 ) to get access to the remote side of the ipsec sa ( 10.0.2/24 ). Here is an excerpt of my ipconfig and routing table # ifconfig lo0: flags=8049 mtu 33224 inet 127.0.0.1 netmask 0xff00 inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x6 fxp0: flags=8943 mtu 1500 address: 00:a0:c9:43:07:20 media: Ethernet autoselect (100baseTX full-duplex) status: active inet 10.0.1.1 netmask 0xff00 broadcast 10.0.1.255 inet6 fe80::2a0:c9ff:fe43:720%fxp0 prefixlen 64 scopeid 0x1 fxp1: flags=8943 mtu 1500 address: 00:a0:c9:30:b3:34 media: Ethernet autoselect (10baseT) status: active inet x.x.x.254 netmask 0xfffc broadcast x.x.x.255 inet6 fe80::2a0:c9ff:fe30:b334%fxp1 prefixlen 64 scopeid 0x2 pflog0: flags=141 mtu 33224 pfsync0: flags=0<> mtu 2020 enc0: flags=0<> mtu 1536 tun0: flags=8051 mtu 1500 inet 10.0.3.1 --> 10.0.3.2 netmask 0x # netstat -rn Routing tables Internet: DestinationGatewayFlags Refs UseMtu Interface defaultx.x.x.254 UGS11 1211734 - fxp1 10.0.3/24 10.0.3.2 UGS 031900 - tun0 10.0.3.2 10.0.3.1 UH 10 - tun0 x.x.x.x/30 link#2 UC 10 - fxp1 127/8 127.0.0.1 UGRS00 33224 lo0 127.0.0.1 127.0.0.1 UH 1 392 33224 lo0 10.0.1/24 link#1 UC 110 - fxp0 224/4 127.0.0.1 URS 00 33224 lo0 Encap: Source Port DestinationPort Proto SA(Address/Proto/Type/Direction) 10.0.2/24 0 10.0.1/24 0 0 y.y.y.y/50/use/in 10.0.1/24 0 10.0.2/24 0 0 y.y.y.y/50/require/out where x.x.x.x is the external address of my box, y.y.y.y is the external address of the remote side of the ipsec tunnel. I expected this to be sufficient for the routing from 10.0.3/24 to 10.0.2/24. But it is not. Using tcpdump I see that packets entering the gateway via the openvpn tun0 interface destined to some host on 10.0.2/24 do not get routed to the ipsec tunnel but are routed directly to the external interface, i.e. a packet with source ip = 10.0.3.10 and destination ip 10.0.2.1 is routed as is to the external interface. I assume that the route through the IPSEC SA is not taken into account, as the packet to be routed is not from the internal interface. If there were a way to source-nat the packet when it comes in via the tun interface, i.e. before the routing is done, maybe all would be fine. But I don't know a way to achieve this. The straight forward solution to setup another ipsec tunnel between 10.0.2/24 and 10.0.3/24 is out of reach due to weird administrative constraints. Any suggestions? Thanks Christoph Try something like... (This was goofy the first time I did it, at least it didn't quite make since to me..) route add -net 10.0.2.0/24 10.0.1.1 This will tell the local OS where to send traffic for the 10.0.2.0/24 network, where as isakmpd only will processes traffic inbound to match an SA. (as far as I can tell). Give it a shot, it should work... -Dave
Re: openvpn to ipsec routing question
On Tue, Nov 22, 2005 at 08:31:13PM +0100, Christoph Leser wrote: > Hello, > > the question is about how to route traffic from an openvpn tunnel > to an ipsec tunnel. > > This is my setup: > > The OpenBSD gateway has an internal (10.0.1.1/24 ) > and external (x.x.x.x/30) interface. > > The internal net is NAT'ed to the external interface to provide > internet access to hosts on the internal net. > > Through the external interface an ipsec SA ( security association ) > is established ( tunnel mode ) between my internal net ( 10.0.1/24 ) > and another local net of a remote site ( 10.0.2/24 ). > > So hosts on the internal net can reach hosts on the internet > (being NAT'ed ) as well as hosts on the remote > private net 10.0.2/24 ( not being NAT'ed ). > > Now I have setup an openvpn server on this box. > This openvpn server gives out addresses from yet > another net ( 10.0.3/24 ) to the connected clients. > > Connections from openvpn clients are NAT'Ed to the internal > interface to make them appear as being directly attached > to the local private net ( 10.0.1/24 ). > > So far, it works. > > Now I want the clients on the openvpn subnet ( 10.0.3/24 ) to get > access to the remote side of the ipsec sa ( 10.0.2/24 ). > > Here is an excerpt of my ipconfig and routing table > > # ifconfig > lo0: flags=8049 mtu 33224 > inet 127.0.0.1 netmask 0xff00 > inet6 ::1 prefixlen 128 > inet6 fe80::1%lo0 prefixlen 64 scopeid 0x6 > fxp0: flags=8943 mtu 1500 > address: 00:a0:c9:43:07:20 > media: Ethernet autoselect (100baseTX full-duplex) > status: active > inet 10.0.1.1 netmask 0xff00 broadcast 10.0.1.255 > inet6 fe80::2a0:c9ff:fe43:720%fxp0 prefixlen 64 scopeid 0x1 > fxp1: flags=8943 mtu 1500 > address: 00:a0:c9:30:b3:34 > media: Ethernet autoselect (10baseT) > status: active > inet x.x.x.254 netmask 0xfffc broadcast x.x.x.255 > inet6 fe80::2a0:c9ff:fe30:b334%fxp1 prefixlen 64 scopeid 0x2 > pflog0: flags=141 mtu 33224 > pfsync0: flags=0<> mtu 2020 > enc0: flags=0<> mtu 1536 > tun0: flags=8051 mtu 1500 > inet 10.0.3.1 --> 10.0.3.2 netmask 0x > > > # netstat -rn > Routing tables > > Internet: > DestinationGatewayFlags Refs UseMtu Interface > defaultx.x.x.254 UGS11 1211734 - fxp1 > 10.0.3/24 10.0.3.2 UGS 031900 - tun0 > 10.0.3.2 10.0.3.1 UH 10 - tun0 > x.x.x.x/30 link#2 UC 10 - fxp1 > 127/8 127.0.0.1 UGRS00 33224 lo0 > 127.0.0.1 127.0.0.1 UH 1 392 33224 lo0 > 10.0.1/24 link#1 UC 110 - fxp0 > > 224/4 127.0.0.1 URS 00 33224 lo0 > > Encap: > Source Port DestinationPort Proto > SA(Address/Proto/Type/Direction) > 10.0.2/24 0 10.0.1/24 0 0 y.y.y.y/50/use/in > 10.0.1/24 0 10.0.2/24 0 0 y.y.y.y/50/require/out > > where x.x.x.x is the external address of my box, y.y.y.y is the > external address of the remote side of the ipsec tunnel. > > > I expected this to be sufficient for the routing > from 10.0.3/24 to 10.0.2/24. > But it is not. > > Using tcpdump I see that packets entering the gateway via the > openvpn tun0 interface destined to some host on 10.0.2/24 > do not get routed to the ipsec tunnel but are routed directly > to the external interface, i.e. a packet with > source ip = 10.0.3.10 and destination ip 10.0.2.1 > is routed as is to the external interface. > > I assume that the route through the IPSEC SA is not taken into account, > as the packet to be routed is not from the internal interface. > > If there were a way to source-nat the packet when it comes in > via the tun interface, i.e. before the routing is done, maybe > all would be fine. But I don't know a way to achieve this. > > The straight forward solution to setup another ipsec tunnel > between 10.0.2/24 and 10.0.3/24 is out of reach > due to weird administrative constraints. > > Any suggestions? I'm not certain about what to do about the routing, but I'm fairly certain that all your problems would be easily solved if you would just use 10.0.0.0/25 for your internal hosts, and 10.0.0.128/25 for your OpenVPN'ed hosts. Of course, this would require some reconfiguring on the clients/DHCP server/whatever, but it should work. Especially since anything but the router already expects to find OpenVPN clients on 10.0.0.0/24. Otherwise, I see a route-to option in pf.conf(5), which might be used for explicitly sending packets over encap0... of course, you'd still need to do NAT or weird stuff would happen, but this might at least get the routing right. And NAT can come later, if ne
openvpn to ipsec routing question
Hello, the question is about how to route traffic from an openvpn tunnel to an ipsec tunnel. This is my setup: The OpenBSD gateway has an internal (10.0.1.1/24 ) and external (x.x.x.x/30) interface. The internal net is NAT'ed to the external interface to provide internet access to hosts on the internal net. Through the external interface an ipsec SA ( security association ) is established ( tunnel mode ) between my internal net ( 10.0.1/24 ) and another local net of a remote site ( 10.0.2/24 ). So hosts on the internal net can reach hosts on the internet (being NAT'ed ) as well as hosts on the remote private net 10.0.2/24 ( not being NAT'ed ). Now I have setup an openvpn server on this box. This openvpn server gives out addresses from yet another net ( 10.0.3/24 ) to the connected clients. Connections from openvpn clients are NAT'Ed to the internal interface to make them appear as being directly attached to the local private net ( 10.0.1/24 ). So far, it works. Now I want the clients on the openvpn subnet ( 10.0.3/24 ) to get access to the remote side of the ipsec sa ( 10.0.2/24 ). Here is an excerpt of my ipconfig and routing table # ifconfig lo0: flags=8049 mtu 33224 inet 127.0.0.1 netmask 0xff00 inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x6 fxp0: flags=8943 mtu 1500 address: 00:a0:c9:43:07:20 media: Ethernet autoselect (100baseTX full-duplex) status: active inet 10.0.1.1 netmask 0xff00 broadcast 10.0.1.255 inet6 fe80::2a0:c9ff:fe43:720%fxp0 prefixlen 64 scopeid 0x1 fxp1: flags=8943 mtu 1500 address: 00:a0:c9:30:b3:34 media: Ethernet autoselect (10baseT) status: active inet x.x.x.254 netmask 0xfffc broadcast x.x.x.255 inet6 fe80::2a0:c9ff:fe30:b334%fxp1 prefixlen 64 scopeid 0x2 pflog0: flags=141 mtu 33224 pfsync0: flags=0<> mtu 2020 enc0: flags=0<> mtu 1536 tun0: flags=8051 mtu 1500 inet 10.0.3.1 --> 10.0.3.2 netmask 0x # netstat -rn Routing tables Internet: DestinationGatewayFlags Refs UseMtu Interface defaultx.x.x.254 UGS11 1211734 - fxp1 10.0.3/24 10.0.3.2 UGS 031900 - tun0 10.0.3.2 10.0.3.1 UH 10 - tun0 x.x.x.x/30 link#2 UC 10 - fxp1 127/8 127.0.0.1 UGRS00 33224 lo0 127.0.0.1 127.0.0.1 UH 1 392 33224 lo0 10.0.1/24 link#1 UC 110 - fxp0 224/4 127.0.0.1 URS 00 33224 lo0 Encap: Source Port DestinationPort Proto SA(Address/Proto/Type/Direction) 10.0.2/24 0 10.0.1/24 0 0 y.y.y.y/50/use/in 10.0.1/24 0 10.0.2/24 0 0 y.y.y.y/50/require/out where x.x.x.x is the external address of my box, y.y.y.y is the external address of the remote side of the ipsec tunnel. I expected this to be sufficient for the routing from 10.0.3/24 to 10.0.2/24. But it is not. Using tcpdump I see that packets entering the gateway via the openvpn tun0 interface destined to some host on 10.0.2/24 do not get routed to the ipsec tunnel but are routed directly to the external interface, i.e. a packet with source ip = 10.0.3.10 and destination ip 10.0.2.1 is routed as is to the external interface. I assume that the route through the IPSEC SA is not taken into account, as the packet to be routed is not from the internal interface. If there were a way to source-nat the packet when it comes in via the tun interface, i.e. before the routing is done, maybe all would be fine. But I don't know a way to achieve this. The straight forward solution to setup another ipsec tunnel between 10.0.2/24 and 10.0.3/24 is out of reach due to weird administrative constraints. Any suggestions? Thanks Christoph
