Re: type-5 las extarnal-tag field

[Dave Katz <[e-mail]>]

Back in prehistory (end of the Reagan years), this was known as the  
"Milo Word" (since Milo Medin was the guy who wanted it put in  
there.)  It was originally intended to be a pre-BGP way of  
controlling external route distribution, by carrying an AS number  
(for example.)  The choice of which externals to distribute back out  
of the domain was made in part by tags added at the point where the  
routes came in.  Yes, in those days people did inject full Internet  
routing into their IGP, but it was a smaller, slower world back then.

Now it's sort of a Rorschach test for routing interactions.


On Jul 14, 2005, at 7:54 PM, Paresh Khatri wrote:

> HI Ajay,
>
> The external route tag is not used by OSPF itself.  It is  
> transparently conveyed with type-5/type-7 LSAs so that applications  
> can make any desired use of it.  One particular application is when  
> you are doing two-way redistribution at multiple points.  In such a  
> case, you could associate a certain tag when redistributing routes  
> into OSPF.  That way, when you are redistributing *from* OSPF into  
> another protocol at some other redistribution point, you can dis- 
> regard the routes that have that tag associated with it.
>
> HTH,
> Paresh.
>
>
>
> -----Original Message-----
> From: Mailing List [mailto:[e-mail]]On Behalf Of  
> tajay
> Sent: Thursday, 14 July 2005 12:07 AM
> To: [e-mail]
> Subject: type-5 las extarnal-tag field
>
>
> hi guys,
> I am not clear about extarnal-route-tag field in the type-5 lsa.  Can
> anyone  just give me some information about that. Also what should be
> the default value of the tag field? where it is useful ..?
>
> thanks
> ajay
>
>
> This communication, including any attachments, is confidential. If
>  you are not the intended recipient, you should not read it - please
>  contact me immediately, destroy it, and do not copy or use any  
> part of
>  this communication or disclose anything about it.
>
>
>