What does the EIGRP stuck in active message mean?
  1. When EIGRP returns a stuck in active (SIA) message, it means that it has not received a reply to a query. An EIGRP neighbour (or neighbours) have not replied to the query for that route.
  2. When the SIA occurs, the router clears the neighbour that did not reply to the query.
Why do you not see OSPF neighbours as FULL/DR or FULL/BDR on serial link?

This is normal. On point-to-point and point-to-multipoint networks, there are no designated routers (DRs) or backup designated routers (BDRs).

What is multicast address for EIGRP and OSPF hello packets:
  1. EIGRP –
  2. OSPF – for all the routers –
  3. OSPF – initial multicast – only for DR and BDR –
What is type-1 and type-2 LSAs in OSPF?
  1. Type-1 LSAs are router LSAs and are generated by each router for the area to which the router belongs.
  2. Type-2 LSAs are network LSAs and are generated by the DR and BDR.
OSPF network types:
  1. Broadcast, multi-access networks: Ehternet, token ring. Single mode operation.
  2. Point-to-point : T1 CAS, ISDN BRI/PRI, single operation mode, no DR/BDR.
  3. Non-broadcast multi-access(NBMA) networks: Frame realy, ATM, MPLS. Five modes of operation.