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3.27.2014

OSPF Areas (Part 5) - NSSA

Links:
RFC 3101 - The OSPF Not-So-Stubby Area (NSSA) Option
RFC 1587 - The OSPF NSSA Option (Obsoleted by 3101)
RFC 2740 – OSPF for IPv6
Cisco - OSPF Not-So-Stubby Area (NSSA)

Breakdown of the NSSA (Not-So-Stubby-Area) Area:
  • Redistribution allowed by ASBRs in NSSA areas
  • NSSA ASBRs generate Type-7 LSAs for all external routes
    • Appears in the routing table as N1 or N2 external.
  • NSSA ABRs convert Type-7 LSAs to Type-5 LSAs before advertising
  • Blocks Type-5 External LSAs and Type-4 ASBR LSAs into the NSSA area
    • Just like Stub, Inter-Area Type-3 LSAs allowed into the area
  • ABRs will not generate a default route (0.0.0.0/0) for the area (by default)
  • All routers in NSSA area must be configured as NSSA to form an adjacency
    • N-Bit is set to 0 in Hello packet
  • Cannot be backbone area (area 0)
  • Virtual links are not allowed to transit NSSA areas

3.24.2014

OSPF Areas (Part 4) - Totally Stubby

Links:
RFC 2328 – OSPF Version 2
RFC 2740 – OSPF for IPv6
Cisco.com - What are OSPF Areas and Virtual Links

 Breakdown of the Stub Area:
  • Blocks Type-5 External, Type-4 ASBR and Type-3 Summary LSAs.
  • ABRs generate a default route (0.0.0.0/0) for the area (Type-3 Summary)
  • Only ABRs for an area are configured for totally stubby areas. 
  • Cannot be backbone area (area 0)
  • Cannot redistribute into totally stubby areas (no ASBRs)
  • Virtual links are not allowed to transit totally stubby areas
  • E-Flag is set to 0 in Hello packet (same as stub)

Solarwinds Thwack - Guest Ambassador - Index

Here is an index of the four SolarWinds Thwack blog post I created. It was a fun experience and hopefully others found it as useful as I did.

Growing Network Complexity and KISS
Automate All the Things!
Improving the Skills and Knowledge of Your Team
Everyone Loves an Awesome Network Diagram

3.17.2014

OSPF Areas (Part 3) - Stub

Links:
RFC 2328 – OSPF Version 2
RFC 2740 – OSPF for IPv6

Breakdown of the Stub Area:
  • Cannot be backbone area (area 0)
  • Cannot redistribute into stub areas (no ASBRs)
  • Virtual links are not allowed to transit stub areas
  • ABRs generate a default route (0.0.0.0/0) for the area
  • Blocks Type-5 External LSAs and Type-4 ASBR LSAs
  • All routers in stub area must be configured as stub to form an adjacency
  • E-Flag is set to 0 in Hello packet

3.10.2014

OSPF Areas (Part 1)

Im starting a series of OSPF post to both follow up on my OSPF network types series (which can be found here) and to also dig deeper into the different areas available within OSPF and how each controls what LSAs and routes enter and exit an area.

Throughout these post Im going to run both IPv4 and IPv6 side-by-side in order to demonstrate both OSPFv2 and OSPFv3 and their minor differences.

Solarwinds Thwack - Guest Ambassador Post Two


This post hits on the hot topic of network automation. Im excited for this post and hope some good discussion comes out of it.

Automate All the Things!


3.03.2014

Solarwinds Thwack - Guest Ambassador

If anyone is interested I am doing a short guest series over at SolarWinds Thwack. My focus for this series is the growing complexity of networks and how to still build in simplicity. Far from my CCIE studies right now but its nice to have something else to focus on and rest my mind from the grind.

I will push one post a week during the month of March. These post are intentionally open-ended to hopefully stir up some good discussion. I encourage anyone who is interested to jump into the conversation.

I will also link to each article from here.

Here is number one
Growing Network Complexity and KISS