[quagga-dev 3869] Re: Configure rtadv from another software

Romain KUNTZ kuntz at sfc.wide.ad.jp
Tue Dec 6 04:01:29 GMT 2005


Hello,

Paul Jakma wrote:
>> Maybe someone will be interested in such feature, so here is patch 
>> against quagga-0.99.2 that allows dynamic advertisement of new 
>> prefixes: 
>> http://software.nautilus6.org/packages/quagga/quagga-0.99.2-netlink-rtadv.tar.bz2 
>>
>  
> Could you supply a diff of your changes against CVS? Bonus points if 
> your diff also patches relevant ChangeLog files (the more complete your 
> patch is, the easier it is for lazy maintainers to apply it ;) ).

I first have to re-write some part of the code (I currently use the 
libnetlink and libpthread, which can be avoided using some of the quagga 
functions). Then I can provide a patch against CVS if changes are 
accepted by mainteners.

>> Basically, a new Interface Command is available for neighbor 
>> discovery. When activated, rtadv listens to rtnetlink. When an address 
>> is added to an interface, the prefix the address is configured from is 
>> automatically advertised on the link. When the address is deleted, the 
>> prefix is not advertised anymore.
>>
>> The motivation is for example when you use prefix delegation for IPv6, 
>> you do not need to configure rtadv once you received your prefixes and 
>> configured your interface's address.
> 
> 
> Good idea.

Actually this is quite limited. For example you cannot tune the RA 
options such as the lifetime advertised in the RA etc. So I am not sure 
this feature is really usable in the real world.

> Another neat idea would be to key RAs according to the present of a 
> route in the table. Eg imagine:
> 
>     ISP1    ISP2
>            \    /
>             \  /
>             Router
>               |
>           <internal IGP cloud>
>                   .
>                   .
>                   .
>           <several internal>
>           < hops away..   >
>            | /    \ |   |
>            R1      R2---R3   <etc>
>            |       |    |
>          ----    ---------   <end host networks>
> 
> Imagine this site gets two /48 prefixes from its ISPs. The site is an 
> enterprise site, not just a simple, flat end-user. It's end-user 
> networks, on which RAs are desireable and the routers servicing them, 
> are at least one hop away from the "border" routers.
> 
> How are R1, R2, R3, etc. to know which prefixes to advertise?
> 
> One way might be to key advertisement based on whether prefixes are 
> available in IGP.
> 
> Interested? :)


In my environment (Mobile Networks) I cannot use such idea. I do not 
know if you are familiar with NEMO, but the Mobile Routers have a tunnel 
to their home agent in which usually no route are advertised.
Using the "dynamic routing" mode in NEMO may match your scenario. 
However this mode is not implemented in the implementation I use :P

Romain



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