LSA Type 1 (Router LSA):generated by each router for each area it is located.

LSA Type 2  (Network  LSA): generated by DR , link-state ID will be the interface IP address of the DR.

LSA Type 3 (Summary LSA): generated by ABR’s and flooded into other areas throughout the Autonomous System.

LSA Type 4  (ASBR Summary LSA): generated by ABR’s. To find the ASBR by other routers, ABR will generate a summary ASBR LSA including the router ID of the ASBR in the link-state ID field.

LSA Type 5  (Autonomous System External LSA): generated by ASBR and contains routes to networks that are external to current AS.

LSA Type 6  (Multicast OSPF LSA): not supported and not used(Used only for multicast applications).

LSA Type 7  (NSSA External LSA): generated by the ASBR in a not so stubby area.

LSA Type 8 (External attributes LSA for BGP): Used to work with BGP.

LSA Type 9,10,11 (Opaque LSAs)

Below table summarizes OSPF LSA Types –

Related – OSPF CHEATSHEET

iBGP is abbreviation for Internal Border Gateway Protocol. iBGP protocol is used between the routers within the same autonomous system (AS). iBGP speaking Routers need to form full mesh to maintain full routing information. Full mesh (iBGP neighborship with all Routers in same AS) can be mitigated by using either Route reflectors or BGP confederation.

Key Features of iBGP:

iBGP Neighborship: Both the routers forming iBGP needs to be in the same Autonomous System.

iBGP Advertisement: A route learnt from an iBGP peer will not be advertised back to another iBGP neighbor by default.

iBGP Scope: iBGP is used within the same organisation.

iBGP Administrative Distance: iBGP routes have administrative distance of 200.

iBGP Toplogy: iBGP requires full mesh or else either of route reflectors or BGP confederation.

iBGP TTL: iBGP TTL is set at 255 by default

Continue Reading:

What is eBGP ?

eBGP vs iBGP

In case you are preparing for your next interview, then our cheatsheet on BGP would be really helpful for you as a ready reckoner. Please download BGP CHEATSHEET FREE PDF 

If you want to learn more about MPLS, then check our e-book on BGP Interview Questions and Answers in easy to understand PDF Format explained with relevant Diagrams (where required) for better ease of understanding.

eBGP is abbreviation for External Border Gateway Protocol and is one of the flavors of BGP protocol. eBGP Routing protocol is used between BGP speaking neighbors which belong to different ASNs (Autonomous System Numbers). eBGP functions as the protocol for interconnection of networks from different organizations.

Key Features of eBGP:

eBGP Neighborship: Both the routers forming eBGP neighborship should be in separate Autonomous Systems.

eBGP Route Advertisement: A route learnt from an eBGP peer will be advertised back to another iBGP or  eBGP neighbor by default.

eBGP Scope: It is used between organization, or between organization and ISP(Internet Service Provider).

eBGP Administrative Distance: eBGP routes have administrative distance of 20.

eBGP Topology: It does not require full mesh neighborship.

eBGP TTL: By default eBGP TTL value is 1 which means that neighbors(routers) should be directly connected. When the two neighbors/routers are not directly connected then we can still make it work but we’ll have to use multihop.

Continue Reading:

What is iBGP?

eBGP vs iBGP

In case you are preparing for your next interview, then our cheatsheet on BGP would be really helpful for you as a ready reckoner. Please download BGP CHEATSHEET FREE PDF 

If you want to learn more about MPLS, then check our e-book on BGP Interview Questions and Answers in easy to understand PDF Format explained with relevant Diagrams (where required) for better ease of understanding.