Remote-Bridging(1).pdf

Remote Bridging with IP Tunnels mini−HOWTO

Alexander Alekseev

alex@zapad.msk.ru

v1.0, May 12, 2002

Revision History

Revision 1.0

2002−05−12

Revised by: aa

first release

This document describes how to unite two separate ethernet LANs with an IP tunnel between them.

Remote Bridging with IP Tunnels mini−HOWTO

Table of Contents

1. How does it work?. ..........................................................................................................................................1

1.1. Bridging IP over ethernet traffic between 2 LANs.. .........................................................................1

1.2. What about other protocols?. ............................................................................................................3

2. Copyright. ........................................................................................................................................................4

2.1. GNU Free Documentation License. ..................................................................................................4

2.2. PREAMBLE. ....................................................................................................................................4

2.3. APPLICABILITY AND DEFINITIONS. ........................................................................................4

2.4. VERBATIM COPYING. ..................................................................................................................5

2.5. COPYING IN QUANTITY. .............................................................................................................5

2.6. MODIFICATIONS. ..........................................................................................................................6

2.7. COMBINING DOCUMENTS.. ........................................................................................................7

2.8. COLLECTIONS OF DOCUMENTS. ..............................................................................................8

2.9. AGGREGATION WITH INDEPENDENT WORKS. .....................................................................8

2.10. TRANSLATION.. ...........................................................................................................................8

2.11. TERMINATION. ............................................................................................................................8

2.12. FUTURE REVISIONS OF THIS LICENSE. .................................................................................9

2.13. How to use this License for your documents. .................................................................................9

1. How does it work?

You can transparently bridge traffic between 2 ethernet LANs to unite them, if both of them are connected to

Internet.

There is no way to do a "real" bridge, you can only bridge third level protocols, which linux knows how to

route, but ethernet traffic with those protocols will seem bridged. You can make 2 ethernet bridges, to bridge

IP and/or IPX traffic. You cannot transparently bridge any other third level protocols between distinct LANs.

You should read the rest of this document to determine whether you can bridge any other protocol.

1.1. Bridging IP over ethernet traffic between 2 LANs.

If you have:

PC1 (192.168.0.1 /24)−−|

PC3 (192.168.0.3 /24)−−|

PC5 (192.168.0.5 /24)−−|−−[ eth0 − bridge_1 − eth1 (195.0.0.1) ]

PC253 (192.168.0.253/24)−−|

| (192.168.0.2 /24) PC2

| (192.168.0.4 /24) PC4

[ (192.0.0.1) eth1 − bridge_2 − eth0 ] −−| (192.168.0.6 /24) PC6

| (192.168.0.254/24) PC254

bridge_1 and bridge_2 are your Linux bridges and externally connected to the Internet interface eth1. So

195.0.0.1 and 192.0.0.1 can be any valid Internet addresses given to you by your ISP.

So, you should:

Get two linux computers with kernels 2.2 or 2.4. Kernels should be compiled with PPP and

Advanced Router. You also need the iproute2 package properly installed. Information on

iproute2 can be found in Configure.help of your kernel in the comments under Advanced

Router. You also need the following utilities:

¨ PopTop (PPTP server) − http://poptop.lineo.com

pppd (PPP daemon) − ftp://cs.anu.edu.au/pub/software/ppp/

¨ PPTP (Linux PPTP Client, by C.S. Ananian) −

http://www.pdos.lcs.mit.edu/~cananian/Projects/PPTP/

tarpd (a trivial proxy arp daemon) − htp://www.cs.hut.fi/~tricky/utils/net/tarpd−1.6.tar.gz

You can also find them on http://www.freshmeat.net

Please, keep in mind that you need special patches for pppd and the kernel if you want to do MS

Chap and MS Encryption (MPPE). Refer to the PoPTop manual for instructions on how to get and

install these patches.

Connect your routers to Internet, or establish any other communication between them with the

exception of IP.

1. How does it work?

Remote Bridging with IP Tunnels mini−HOWTO

Make a PPTP tunnel between them. There are example configurations in the PoPToP (server) and

pptp (client) manuals.

Now you should have two bridges and an IP tunnel between then, possibly encrypted (refer to the

PPP manual). Let's configure bridging.

Remember that the bridge is really a router, so we need to run the following commands on our

bridges (this assumes bridge_1 and bridge_2 are IP addresses, assigned to each end of the

PPTP tunnel between bridges):

bridge_1$ip route add 192.168.0.2 via bridge_2

bridge_1$ip route add 192.168.0.4 via bridge_2

bridge_1$ip route add 192.168.0.6 via bridge_2

bridge_1$ip route add 192.168.0.254 via bridge_2

bridge_1$ip route add 192.168.0.255 via bridge_2

On the other side:

bridge_2$ip route add 192.168.0.1 via bridge_1

bridge_2$ip route add 192.168.0.3 via bridge_1

bridge_2$ip route add 192.168.0.5 via bridge_1

bridge_2$ip route add 192.168.0.253 via bridge_1

This will tell each of bridges which hosts are on the other side. You can do the same with the

old−style route command. It will look like:

bridge_1$route add −host 192.168.0.2 gw bridge_2

bridge_1$route add −host 192.168.0.4 gw bridge_2

bridge_1$route add −host 192.168.0.6 gw bridge_2

bridge_1$route add −host 192.168.0.254 gw bridge_2

bridge_1$route add −host 192.168.0.255 gw bridge_2

On the other side:

bridge_2$route add −host 192.168.0.1 gw bridge_1

bridge_2$route add −host 192.168.0.3 gw bridge_1

bridge_2$route add −host 192.168.0.5 gw bridge_1

bridge_2$route add −host 192.168.0.253 gw bridge_1

Please note once more that bridge_1 and bridge_2 are not IP addresses given by your ISP, but IP

addresses which you assigned to each end of the PPTP tunnel.

Now you have two bridges and each of them knows where to find a particular IP. But how do you tell

those computers to send their traffic for the remote network to the local bridge? You need tarpd.

tarpd is a very simple daemon, which replies to arp requests for certain IP addresses. You only

need to run a tarpd on each bridge, and specify the list of IP addresses found on the remote end.

For example, for those two bridges you should run:

1. How does it work?

Remote Bridging with IP Tunnels mini−HOWTO

bridge_1$tarpd eth0 192.168.0.2 255.255.255.255 \

192.168.0.4 255.255.255.255 \

192.168.0.254 255.255.255.255

On the other side:

bridge_2$tarpd eth0 192.168.0.1 255.255.255.255 \

192.168.0.3 255.255.255.255 \

192.168.0.253 255.255.255.255

You specify 128 remote pairs (IP/mask. Mask should be 255.255.255.255 in order not to confuse

tarpd!) on each bridge.

Enjoy your bridges!

1.2. What about other protocols?

Really, I can say nothing about other protocol routing. I never used them. But I suppose if you are familiar

with other protocols, it should not be too difficult to bridge it this way.

1.2. What about other protocols?

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: