bird: show route behaviour

[Ondrej Filip]

On 24.2.2013 19:35, Hans van Kranenburg wrote:
>> yes, because 'table master' is default. I produced a simple patch
>> (attached) against the current git repository, but it should work
>> against 1.3.9.  However I am not 100% sure whether to submit this into
>> the main branch or rather just document that 'table master' is
>> default. I will discuss it with my teammates. And of course, your
>> comments are welcome.
> 
> How should the output of the following command in Dans example be
> interpreted?
> 
> bird> show route export nix1_nix
> 4.4.4.0/24         via 172.17.1.1 on eth0 [s_master 00:29] * (200)
> 5.5.5.0/24         via 172.17.1.1 on eth0 [s_nix 00:29] * (200)
> 6.6.6.0/24         via 172.17.1.1 on eth0 [s_tranzit 00:29] * (200)
> 
> I guess it should be done like: "these are the routes that could
> possibly be exported from table master via table t_nix to nix1_nix if
> none of them were being filtered"? This does not make any sense to me as
> default output.

No, that are routes from master table that could be exported to
protocol nix1_nix filtered by import protocol. But anyway.

> The config Dan is showing explicitely has an import none from master to
> t_nix, so when being busy to debug route information at the nix1_nix
> proto, after filtering all those routes from t_nix to nix1_nix (possibly
> to isolate the test case while tracking down a problem) this looks very
> confusing.
> 
> I'm always a fan of defaults that match how (new) people would use the
> software intuitively, and here's how I would intuitively think:
> 
> One of the first pages you read when starting with bird is this one:
> 
> http://bird.network.cz/?get_doc&f=bird-2.html
> 
> "Each protocol is connected to a routing table through two filters which
> can accept, reject and modify the routes. An export filter checks routes
> passed from the routing table to the protocol, an import filter checks
> routes in the opposite direction."
> 
> This makes me think by default that show route export <protocol> would
> show me information about what is actually going in in <protocol> right
> now by default, related to its own connected bird table.
> 

OK. I understand your point.

			Ondrej