Solved: Router with multiple DSL uplinks

CyberLeo Kitsana cyberleo at
Wed Mar 7 23:41:20 UTC 2007

CyberLeo Kitsana wrote:
> Hi!
> I'm trying to configure a NAT router with multiple DSL uplinks from
> the same provider. Everything seems to work properly, except when
> connecting via PPPoE--the second link to come up receives an error
> while attempting to configure the second tun interface, as both links
> assign addresses in the same subnet and to the same peer.
> Is there some configuration or trick I can use to coerce the router to
> bring up both links properly?
> PPp ON router1> Warning: iface add: ioctl(SIOCAIFADDR, xx.xx.xx.230/24
> -> File exists
> Error: ipcp_InterfaceUp: unable to set ip address

This is caused by multiple ptp interfaces with the same peer address
( in the above example). At least with SBC (AT&T), the actual
IP there doesn't really matter, as it's just a way for the kernel to
determine which interface to send the packet out on, and the other side
will route the packet regardless.

A simple iface up-script in mpd to change the peer IP to something else
on each instance fixes the error nicely.

This was for a multi-homed router project (2-4 DSL links, without ISP
cooperation) that turns out to be quite functional. Details are at the
following URL, for anyone interested (only notes for now):


Fuzzy love,
Technical Administrator
CyberLeo.Net Webhosting
<CyberLeo at CyberLeo.Net>

Furry Peace! -

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