Configuration ADSL pour Free sur Cisco 1841

(an english translation for this article is here)

Les clients de Free sont généralement contents… jusqu’a ce qu’ils aient besoin de support. C’est un problème avec tous les providers, mais chez Free en général, c’est gratiné.

Quand vous vous abonez chez Free, vous recevez une belle Freebox : un equipement faisant office de modem DSL, routeur, de FXS pour brancher le téléphone et parfois plus si vous avez la chance d’avoir la TV et d’autres services.services.

Mais quand vous ne voulez pas utiliser la FreeBox, ou qu’elle est morte, il y a des moyens alternatifs pour se connecter. Le plus simple c’est de trouver un modem DSL (un speedtouch par exemple), et d’utiliser un routeur pouvant faire du PPPoE (un Linksys WRT54GL + firmware tomato par exemple).

Vous pouvez aussi faire du PPPoA si vous avez un routeur avec une interface ATM. La configuration ci dessous peut être utilisée sur un routeur Cisco 1841 avec une carte ATM pour se connceter chez Free. La conf est facilement adaptable à d’autre modèles, le changements se limitant souvent aux noms d’interfaces.

Vous pouvez debugguer la connexion en tapant :

Bonne chance.

Cisco 1841 ADSL configuration for Free telecom

(a french translation for this article is here)

http://leucos.lstilde.org/wp/2009/05/cisco-1841-ads…r-free-telecom/

People connected via Free, a french internet provider are usually happy customers… until they need to get support. Well, this is a problem with most of providers out there.

When you subscribe to Free, they send you a Freebox : a combo containing a DSL modem, a router, an FXS to hook your telephone, and sometimes more if you’re lucky enough to have TV and other services.

But when you don’t want to use this box, or when it’s dead, you can use alternate ways to get connected. The easiest one if to get a DSL modem (a speedtouch for instance), and use a PPPoE capable routeur (like a Linksys WRT54GL + tomato firmware).

You can also do PPPoA if you have a router with an ATM interface. The configuration included below can be used on a Cisco 1841 routeur with ATM card to connect to Free. It probably can be adapted to other models  very easily by changing only interface names.

You can debug what happens by issuing :

Good luck.

Fixing ‘IPSEC(initialize_sas): Invalid Proxy IDs’ with dynamic VPNs

Dynamic VPNs is a Cisco feature that makes a central router accept VPN establishment without specifying a peer or an ACL for the SA.

The configuration is very simple (even simpler than normal, statically specified tunnels) so when the tunnel doesn’t come up, it is quite frustrating.

And when you get ‘IPSEC(initialize_sas): Invalid Proxy IDs’, meaning SA ACL doesn’t match on both sides, you start to pull your hairs out : how can’t they match when they are not needer on the headend side ??

Well, it seems that the headend is checking the remote SA specification (Proxy ID) anyway, and bails out from isakmp when things go wrong.

Consider this log, saw on a router sitting at 172.22.1.130/27 with

and

See it ?

the subnet mask 255.255.255.193 comes from a wrong ACL specification :

instead of

So 255.255.255.193 last byte yields a discontinuous mask (11000001) which is not so commonly used
That’s why the tunnel is not coming up, and how you lost the last hour.

Cisco serial cable pinout

Here is the pinout for the standard Cisco serial console cable (DB9 – RJ45) like this one.

Note that DCD(1) and RI(9) are not wired.

This cable is quite handy when doing µcontroller stuff. Just put a RJ45 socket on your PCB our get a breakout board from Sparkfun and you can plug and unplug at will and securely.