I have been using tunneling from my laptop to a server in my office,
both running kernel 2.0.x, without any problems.

I'm now trying to upgrade my laptop to kernel 2.2.1, and am having
trouble figuring out how to set up my side of the tunnel.  I've look in
the mailing list archives and downloaded
ftp://ftp.inr.ac.ru/ip-routing/iproute2-current.tar.gz, but haven't
found anything to explain the overall approach for configuring tunnels
under the new kernel.

In my current setup, I am tunneling one IP number for my laptop, which
does not have an ethernet interface (only the PPP link).

 tunl0: aaa.aaa.aaa.LLL
  laptop         
     |
     | ppp: zzz.zzz.zzz.PPP
     |
  (internet)
     |
     | eth0: aaa.aaa.aaa.EEE
     |
  server
 tunl0: aaa.aaa.aaa.SSS

Where all the addresses are the same from session to session except 
zzz.zzz.zzz.PPP, which is dynamically assigned by my ISP.


On the laptop, my routes look like:
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
zzz.zzz.zzz.PPP *               255.255.255.255 UH    0      0        0 ppp0
aaa.aaa.aaa.SSS *               255.255.255.255 UH    0      0        3 ppp0
default         *               0.0.0.0         U     0      0        5 tunl0

If config looks like:
ppp0      Link encap:Point-to-Point Protocol  
          inet addr:zzz.zzz.zzz.PPP  P-t-P:zzz.zzz.zzz.xxx Mask:255.255.255.0
[...]
tunl0     Link encap:IPIP Tunnel  HWaddr   
          inet addr:aaa.aaa.aaa.LLL  P-t-P:aaa.aaa.aaa.SSS Mask:255.255.255.255
[...]


(On the server, they look like:
aaa.aaa.aaa.SSS 0.0.0.0         255.255.255.255 UH    0      0        0 eth0:0
aaa.aaa.aaa.LLL 0.0.0.0         255.255.255.255 UH    0      0        4 tunl0
aaa.aaa.aaa.0   0.0.0.0         255.255.255.0   U     0      0     4995 eth0
default         aaa.aaa.aaa.gw  0.0.0.0         UG    1      0    70137 eth0

and
tunl0     Link encap:IPIP Tunnel  HWaddr   
          inet addr:aaa.aaa.aaa.SSS  P-t-P:zzz.zzz.zzz.PPP Mask:255.255.255.0
[...]
On the server, I also do:
   arp -s aaa.aaa.aaa.LLL -D eth0 pub

)

When I reboot with 2.2.1 on the laptop and issue the following commands:
   insmod ipip
   ip tunnel add tunl1 mode ipip remote aaa.aaa.aaa.SSS local zzz.zzz.zzz.PPP
   ifconfig tunl1 aaa.aaa.aaa.LLL
   
and then add a route to some address, say
   add route -host aaa.aaa.aaa.EEE dev tunl1

and then watch the PPP link with tcpdump, it looks like packets to
aaa.aaa.aaa.EEE are correctly sent to aaa.aaa.aaa.SSS as encapsulated
packets.  However, packages that arrive for LLL cause the generation of
"protocol ## not available" ICMP replies.  The same happens if I ping
aaa.aaa.aaa.LLL from the server.  I assume this means the tunnel is
somehow not active on the laptop end.

I tried "echo 1 > /proc/sys/net/ipv4/ip_forward", but it didn't seem to
make any difference.  I also browsed the Alan Cox patches
(patch-2.2.1-ac5) but it didn't look like ipip.c or ip_forward.c 
get patched so I'm thinking its not necessary for what I'm trying to do.

My questions:

1. What am I missing?

2. Is there a web site or document I should be looking at for this info?

3. Do I need patches to get ipip tunneling to work in 2.2.1?

4. Is 2.0.x ipip.o/new_tunnel.o tunneling interoperable with 2.2.1 mode ipip
   tunneling?

5. Where can I find more info on the "ip" command?  (I didn't find any
   documentation on it in the iproute2 package, or in that directory
   on the FTP site.)

6. I have seen mention if "iptunnel" and "iproute" commands in the
   mailing list archives. Are these just earlier incarnations of 
   utilities that have since been combined in the iproute2 "ip"
   command?


Thanks.

                                                Nathan
----------------------------------------------------------------------------
Nathan Treadway    | Ray Ontko & Co. | Software consulting services
[EMAIL PROTECTED]  | Richmond, IN    | http://www.ontko.com/   
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