RE: VPN between multiple LANs

> Remember, each endpoint has TWO IP addresses associated with 
> it:  the "transport" IP address (usually a public IP 
> address), and the "tunnel" IP address (usually a private IP address).
> 
> The gateway systems need to be able to talk to each other, so 
> the default route to the internet must exist, so that the 
> transport IP addresses can talk to each other.  Once you have 
> that, you would set up a route to each LAN using your tunnel 
> IP addresses.

As you can see in the routing table below...  (I left the old quotes in
place deliberately)
> 
> > -----Original Message-----
> > From:	Tony Langdon (ATC) [SMTP:[email protected]]
> > Sent:	Wednesday, January 26, 2005 1:44 PM
> > To:	'Mark'; 'Tony Langdon (ATC)'; '[email protected]'
> > Subject:	RE: VPN between multiple LANs
> > 
> > > If you use the same IP for all cipe adapters, what do you 
> route by?
> > 
> > I'm not sure I see the problem.  Routing is based on 
> _destination_ IP 
> > address (let's leave policy routing aside for the moment, 
> though that 
> > isn't an issue either in the real world), and all tunnels lead to 
> > different IPs on
> > the remote end.
> > 
> > Here's a real world example.  4 networks linked in total, 3 
> CIPE links 
> > between each of the remote network and the local network.  In all 
> > cases, the CIPE devices are using the same IP address.
> > 
> > I've added some comments
> > 
> > Kernel IP routing table
> > Destination     Gateway         Genmask         Flags 
> Metric Ref    Use
> > Iface
> > 
> > Host routes to remote tunnel endpoints.
> > 192.168.7.1     0.0.0.0         255.255.255.255 UH    0     
>  0        0
> > cipcb2
> > 10.200.200.2    0.0.0.0         255.255.255.255 UH    0     
>  0        0
> > cipcb0
> > 192.168.181.1   0.0.0.0         255.255.255.255 UH    0     
>  0        0
> > cipcb1
> > 
> > Network routes for cipcb0
> > 202.12.87.160   10.200.200.2    255.255.255.248 UG    0     
>  0        0
> > cipcb0
> > 202.12.87.152   10.200.200.2    255.255.255.248 UG    0     
>  0        0
> > cipcb0
> > 
> > Local LAN routes
> > 192.168.15.0    0.0.0.0         255.255.255.128 U     0     
>  0        0
> > eth0
> > 192.168.15.128  0.0.0.0         255.255.255.128 U     0     
>  0        0
> > eth0
> > 
> > Network route for cipcb1
> > 192.168.181.0   192.168.181.1   255.255.255.0   UG    0     
>  0        0
> > cipcb1
> > 
> > Network route to ISP
> > 211.28.37.0     0.0.0.0         255.255.255.0   U     0     
>  0        0
> > eth1
> > 
> > Linux seems to setup an autoconfig route for some reason..
> > 169.254.0.0     0.0.0.0         255.255.0.0     U     0     
>  0        0
> > eth1
> > 
> > Network route for cipcb2
> > 192.168.0.0     192.168.7.1     255.255.0.0     UG    0     
>  0        0
> > cipcb2
> > 
> > Looopback
> > 127.0.0.0       0.0.0.0         255.0.0.0       U     0     
>  0        0 lo
> > 
> > Default route (Internet)
> > 0.0.0.0         211.28.37.1     0.0.0.0         UG    0     
>  0        0
> > eth1
> > 
> > Oh, and the interfaces...
> > 
> > OK, the first one is using an oddball address, but that's 
> because it's 
> > linked to a Windows host on the far end, which had to work 
> that way, 
> > not because I had routing issues on my end.
> > 
> > cipcb0    Link encap:IPIP Tunnel  HWaddr
> >           inet addr:10.200.200.1  P-t-P:10.200.200.2  
> Mask:255.255.255.255
> >           UP POINTOPOINT NOTRAILERS RUNNING NOARP  MTU:1442 
>  Metric:1
> >           RX packets:0 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:4315 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:100
> >           RX bytes:0 (0.0 b)  TX bytes:465732 (454.8 Kb)
> > 
> > The rest use the same IP as eth0
> > 
> > cipcb1    Link encap:IPIP Tunnel  HWaddr
> >           inet addr:192.168.15.1  P-t-P:192.168.181.1 
> > Mask:255.255.255.255
> >           UP POINTOPOINT NOTRAILERS RUNNING NOARP  MTU:1442 
>  Metric:1
> >           RX packets:155401 errors:1 dropped:0 overruns:0 frame:1
> >           TX packets:167960 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:100
> >           RX bytes:12743584 (12.1 Mb)  TX bytes:22187936 (21.1 Mb)
> > 
> > cipcb2    Link encap:IPIP Tunnel  HWaddr
> >           inet addr:192.168.15.1  P-t-P:192.168.7.1  
> Mask:255.255.255.255
> >           UP POINTOPOINT NOTRAILERS RUNNING NOARP  MTU:1442 
>  Metric:1
> >           RX packets:2716998 errors:1409 dropped:0 
> overruns:0 frame:1409
> >           TX packets:3038908 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:100
> >           RX bytes:460282800 (438.9 Mb)  TX bytes:400079776 
> (381.5 Mb)
> > 
> > And for reference....
> > 
> > eth0      Link encap:Ethernet  HWaddr 00:E0:29:9D:BA:4F
> >           inet addr:192.168.15.1  Bcast:192.168.15.127 
> > Mask:255.255.255.128
> >           inet6 addr: 2001:388:c027:1::1/64 Scope:Global
> >           inet6 addr: fe80::2e0:29ff:fe9d:ba4f/64 Scope:Link
> >           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
> >           RX packets:5209146 errors:0 dropped:0 overruns:0 frame:0
> >           TX packets:5225013 errors:0 dropped:0 overruns:0 carrier:0
> >           collisions:0 txqueuelen:100
> >           RX bytes:584746849 (557.6 Mb)  TX 
> bytes:1748568057 (1667.5 Mb)
> >           Interrupt:9 Base address:0x9000
> > 
> > --
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> 

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