OSPF Lsa Type 2

[surendrasinghtanwar667]

Hi, I have a question. If there is a DR, then LSA type 2 will be sent to all other routers, but why is DROTHER also sending individual LSA Type 1? I understand LSA Type 2 a little bit, which is that it is used to obtain the information of the router presented in the same subnet and multicast network.

[surendrasinghtanwar667]

This is the topology where two transit area are there so according to this topology when i check the ospf LSDB Database then i am able to see all router LSA Type 1in R1 LSDB. So my question was that if all routers are sending LSA type 1 to each other so what is the use case of LSA TYPE 2 and why it is being used. 

One more question is in transit area or multiaccess area type 2 lsa is generated so what information is shared with DR on that time does all DROTHER router share LSA type 1 information to DR and that information is being shared in the form of lsa type 2 .

[Cristian Matei]

Hi,

    First, i'd say is important to clarify LSA Type 1 vs. LSA Type2, when we speak about OSPFv2. Each router will always send one LSA Type 1 per area, advertising all of its links, link type, associated prefix and cost within that area. Additionally, for each network segment where there is DR election, DR will advertise one LSA Type2, which contains all routers attached to that network segment and the network mask of the prefixes attached to that network segment.

  To your given example, where R1 is the only router connected to R6, assuming all links are part of same area, R1 will be the router flooding all Type 1 LSA's as well as Type 2 LSA to R6.

Cristian.

[paul driver]

Hello @Cristian Matei 
thanks for the sanity check.