Re: Again two ADSL lines, routing problems

Andrea Venturoli wrote:
Hello.
I have a setup where a FreeBSD box is connected to two ADSL routers: default gateway is set to the first and, in case of failure, is moved to the other one. This works perfectly for outgoing connections: in the event of the switch, I'll have to reconnect, but that's acceptable.

The problem is in the incoming connections: if I get one on the "backup" router, this will reach the server, which will however answer through its "default" router. Thus the remote client will see packets coming back from a different host and things won't work.
Just to be clear, the packets travel as follows (with source and dest IP in brackets):
Client (x.x.x.x) -> Backup router (y.y.y.y)
Backup router (x.x.x.x) -> Server (z.z.z.z)
Server (z.z.z.z) -> Default router (x.x.x.x)
Default router (v.v.v.v) -> Client (x.x.x.x)

So the client (x.x.x.x) connects to y.y.y.y (the backup ADSL public IP), but gets answers from v.v.v.v (the master ADSL public IP).


AFAIK there is no solution to this, but I tought I'd ask before giving my official opinion to my customer.
Perhaps there's some sort of hack we could use, that through ipfw/natd/other diverting daemon/whatever delivers answers based on the MAC address of the incoming connections (if the MAC address belongs to the backup router, use that for answers)... does anyone know?

I would propose a nat on the internal interface on the backup router for all incomming trafic -- with pf:

nat on $int_if proto tcp from !192.168.0.0/16 to $internal_server -> $int_if

so the internal server see trafic comming from the backup router and the response go back this way.

Henri

bye & Thanks
av.
_______________________________________________
freebsd-net@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscribe@xxxxxxxxxxx"

_______________________________________________
freebsd-net@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • [LONG - for experts] Configuring redundancy for a /29 public range
    ... I have a single site with two internet connections: ... Primary Line: RFC1483 SHDSL 4Mbit/symmetric ... Backup line: RFC1483 ADSL 2048down/512upload ... First router SHDSL: ...
    (comp.dcom.sys.cisco)
  • Re: ADSL Hard Wired House
    ... And my line will have the ADSL connection, ... My bedroom will of course have my phone line and the ADSL ... So you will either need to use two, or get a router with 6/8 ports ... Or use Wireless for two of the connections. ...
    (uk.telecom.broadband)
  • Re: Is this possible?
    ... please can someone tell me how easy it would be to set up ADSL ... > broadband to serve 2 ... The router is a Cisco, and you'll probably find that the average domestic ... It would probably be cheaper to provide two separate connections. ...
    (comp.sys.acorn.networking)
  • Re: Good ADSL router/card with packet re-writing?
    ... I am after a new ADSL router or card given that I have two ... > connections generated by this work swamps the two domestic ADSL ...
    (uk.comp.os.linux)
  • Re: Good ADSL router/card with packet re-writing?
    ... >connections generated by this work swamps the two domestic ADSL ... I'd say that's more a transport than a router limitation. ... >box but PPPoA means this isn't possible apparently. ...
    (uk.comp.os.linux)