[Babel-users] How to properly add an unreachable route?

[Juliusz Chroboczek]

> 1) Does this also export the default route? (not what I want by default)
>
> redistribute ip 0.0.0.0/0 le 24 allow
> redistribute local deny

Depends on how the DHCP server is installing the route.  If it's using the
"boot" protocol, as it should, Babel will ignore it by default.  In any
case, you can force ignoring the default route by adding the following
*before* the allow:

  redistribute ip 0.0.0.0/0 le 0 deny

> 2) Will this correctly export the default route if I changed it to
> allow? If a box isn't a default gateway should I put in a specific
> deny or allow line? Or use eq as I just did? or?
>
> redistribute ip 0.0.0.0/0 eq 0 deny
> redistribute ip 0.0.0.0/0 le 24 allow
> redistribute local deny

No.  If the DHCP server is doing its job properly, it's marking its routes
with the protocol "boot", which is a hint to proper routing protocols to
ignore the route.

Redistributing a DHCP route over a roting protocol is not robust network
design -- DHCP should be announcing routes derived from a routing protocol,
not the other way around.  However, support for redistributing in the DHCP
to Babel direction was grudgingly added after enough users asked for the
feature (yeah, I know, I'm weak):

  redistribute ip 0.0.0.0/0 le 0 proto 3 allow

(When you don't mention a proto number, the redistribution is taken to
apply to all proto numbers except 3.)

-- Juliusz