ABR & DR in OSPF

[Adam373]

Hi There are some videos and some websites say that the function of Area border router (ARB) is to 1-maintain an LSDB 2- Summarizes LSA Same as Designated Router if so what is the difference between ARB and Designated Router if both do the same thing?if can someone explain in detail

[balaji.bandi]

ABR and DR do not do the same roles.

here is typical with a diagram explained :

https://www.firewall.cx/networking-topics/routing/ospf-routing-protocol/1178-ospf-lsa-types-explained.html

[Thomas Schmitt]

ABR connects different areas and can manipulate advertisments (like a doorkeeper an a door between 2 rooms)  and DR/BDR is responsible for advertisment distribution by multiaccess network types within an area (like an event manager)

[MHM Cisco World]

DR different than ABR, 

What exactly make you think it same?

[Richard Burts]

I agree with previous posts that DR and ABR are not at all the same. A DR operates on a single subnet of the OSPF network and facilitates full synchronization of the LSDB for the neighbors on that network segment. A DR does not do any summarization or any filtering of routes. An ABR has connections on two (or more) areas, one of which must be area zero. An ABR provides routing between the areas and may be configured to do some summarization or filtering of routes advertised between areas.

[Spooster IT Services]

Hi Adam373, 

- An ABR ( Area Border router) , is a router which has one of it's link in AREA= 0 ( backbone area ) and the other link in some other area. It serves as a gateway for communication between two different areas . ABR helps in sharing prefixes within 2 different  areas .  ABR Helps in summarization and filtering of prefixes 

- While a DR is elected per subnet in OSPF network  and their main purpose is to reduce the number of adjacencies & reduce the flooding in the network .

[Joseph W. Doherty]

"Hi There are some videos and some websites say that the function of Area border router (ARB) is to 1-maintain an LSDB 2- Summarizes LSA Same as Designated Router if so what is the difference between ARB and Designated Router if both do the same thing?"

As the other posters have noted, ABRs (BTW not ARB) and DRs do NOT do exactly (all) the same things.  However, some information is the same for all OSPF routers regardless of their "role", such as the same area's topology information.

To muddy the waters a bit further, if you're not already aware, an ABR can also be a DR (and I believe you could also include an ASBR role in any combination with ABR or DR too).