When you redistribute routes between routing protocols you usually tag the routes redistributed using a route map. and then deny the tags on a redistibution back into the originating routing protocol.
I tried doing this with BGP and noticed that the TAGs were not sent across the EBGP connection.
Is there a way to get these TAGs sent across a BGP network or do we have to use them to set BGP communities etc?
The tag is not a BGP attribute, hence it not being carried in the BGP update.
The BGP community attribute is similar to the tag though and can be used to carry arbitrary information between BGP peers.
Hope this helps,