Orhan Ergun 1 Comment

What is DFZ (Default Free Zone)?

In the context of the Internet and BGP routing, DFZ – commonly known as Default Free Zone – refers to the collections of all the public IPv4 BGP prefixes without default route on the global Internet.

Most of the time, you hear full-route or full-Internet-route terms which are the same with Default Free Zone term. Having all BGP routes, which are announced by all the available AS (Autonomous System), on the Internet.

Currently, there are more than 600,000 IPv4 BGP routes and about 30,000 IPv6 routes in the DFZ (Default Free Zone).  These numbers, however, could easily be reduced to 300,000 for IPv4 and less than 20,000 for IPv6 based on the CIDR reports (IPv4 CIDR report and  IPv6 CIDR report). Read more

Orhan Ergun 9 Comments

BGP Design Case Study

Below BGP design case study is taken from the Orhan Ergun’s CCDE Practical Workbook.In the new version of the workbook there are more than 50 case studies are shared for many technologies.

If you are in the network design field or want to learn about it,don’t miss the book.

Scenario :
Network A is a customer of Network Z, Network B is a peer of Network Z.
Network A becomes transit customer of Network B.
Network A announces aggregate to Network Z and more specific prefixes, and to Network B. Network B sends more specific to its peer Z.
Network Z only announces the aggregate to the world. Network B doesn’t announce anything to the upstream SP.

What is the impact of this design ?
Is there any problem ? If there is , how you can fix ? 

Read more

Orhan Ergun 4 Comments

Routing design

Understanding everything about routing design is no brainer, especially if you have the chart below on your wall.

The table below highlights the pros and cons of each routing protocol. Of course, you need to consider the design attributes shown in Figure A before embarking on routing design.

Should you like the comparison of the routing protocols illustrated in the table below or should you want to see similar comparison for other technologies, feel free to add your comment in the comment section.

Another boon for all my readers!

If you are interested in network design or considering CCDE, CCDP, or CCDA certification, you can subscribe for membership here so that you can peruse all the design resources (Videos , Tests , Case Studies , and E-Books).

Figure A: Comparison of Routing Protocols

Orhan Ergun 4 Comments

BGP Route reflectors and potato routing


If you are designing enterprise, service provider, even datacenter networks you have to understand BGP route reflector.

You want to know what is hot , cold and mash potato routing. Read more

Orhan Ergun No Comments

BGP Outbound Route Filtering ( ORF )

Outbound Route Filtering (ORF) is the BGP capability which is negotiated between BGP neighbours during a session setup.

If during a session setup process BGP ORF ( Outbound Route Filtering ) capability is exchanged , one peer can send a signal to its BGP neighbour about desired or unwanted prefixes.

Assume you are receiving a full BGP table from the neighbouring Internet Service Provider , if they support ORF as a BGP capability and agree with you to use it then you can tell to neighbouring BGP router by sending an update that you don’t want particular BGP prefixes without calling ISP and explaining what you want.

It may seem an easy task but from operational point of view , it can really shorten your time and effort.