Hello Nabarun,
The LSA-6 is not bad, it is just unsupported on Cisco routers.
There is an extension to the OSPF so that it can provide multicast routing capabilities. These extensions are called MOSPF (Multicast OSPF) and a new LSA type, the LSA-6, was introduced to allow a router to indicate its membership in selected multicast groups.
Multicast routing extensions to OSPF, described in RFC 1584, were not widely implemented because of relatively high complexity of the overall mechanism. Today, multicast routing is provided by the PIM multicast routing protocol. I believe Cisco never had a working implementation of the MOSPF. However, Cisco's OSPF implementation does recognize LSA-6 although it does not act upon them. If an LSA-6 is received by a Cisco router, it just prints out a warning message on the console. You can configure it to ignore the LSA-6 completely using the ignore lsa mospf command.
Feel welcome to ask further!
Best regards,
Peter
