RFC, or Request for Comments, are documents published that describe various items surrounding computer networking. Generally, these are memorandums published by the Internet Engineering Task Force.

RFCs can be a great resource. For some unknown reason, most candidates preparing for the CCIE don’t take the time to review these documents, which can be very helpful in assisting with understanding the how and why of various networking components. Perhaps the language is a bit dry, or they prefer books with shiny covers.

There are a variety of status classifications. These include, but are not limited to: standards, informational, best current practices. Some are very serious discussions of the deep inner workings, where others are just there for entertainment, such as RFC 1149 and 2549.

If you aren’t sure whether a RFC is intended to be serious or entertainment, check the date. If it was one from 1 April of any year, most likely it falls into the category of entertainment.


Language is included to define how an item is intended to behave. RFC 2119 lists some of these requirements. Requirements are shown capitalized, and include the following: MUST, MUST NOT, SHOULD, SHOULD NOT, MAY, RECOMMENDED, NOT RECOMMENDED, OPTIONAL.

RFCs are not a “magic bullet” for lab preparation. Most students that are familiar with RFCs tend to be more comfortable with the technologies discussed.

RFCs can be viewed online at a number of sites, including the following:



Most search engines will also give you results for RFCs by number or topic.

Quick quiz.

Four questions on RFCs that most people are generally familiar with. Questions are True or False, and the answers can be found fairly quickly, if you know where to look.

T or F
RFC 3330, which describes Special Use IPv4 Addresses, is obsolete.

T or F
RFC 1812, which discusses requirements for IPv4 Routers, states that subnet bits MUST be contiguous.

T or F
RFC 2827 discusses ingress filtering mechanisms, including the effects of multihoming.

T or F
RFC 1918 does not address security issues.

How did you do? Two of these are true and two are false. If you got all four correct, congratulations. If you’ve never heard of these RFCs, perhaps it is time to do some additional reading.

Bonus Question:

True or False:
Neither Cisco nor Juniper devices are compliant with RFC 5841.

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5 Responses to “What does the RFC say?”

  1. Anantha Subramanian Natarajan says:


    Nice one and thanks ……….Is there a doc/page on cisco or juniper specifying which RFCs they are compliant to ?

    Anantha Subramanian Natarajan

  2. Abhay says:

    Nice Information Thank You! Neither of CISCO or NORTEL are compliant with RFC 5841.

  3. rakesh says:

    Thank you for the insight …


  4. Dani Petrov says:

    Abhay, you’re right, yet RFC 5841 is only compatible while RFC 1149 along with RFC 2549 are used as a backhaul :)

    Now on topic – I fully agree with Marvin, the RFC’s are really good source. For instance, during my CCIE (SP) preparation (which was a while ago) I had read really lot of books, papers, articles and so on to get the OSPF “big picture”. The OSPF RFC was the missing part… It is just a ~200 pages but when I read it – all the information which I had already read – got any sense .. Everything got cleared, like a puzzle game…. You’re adding just a little piece of information in order to complete the “BIG PICTURE” (which in my opinion is the most important thing).
    So I really recommend RFCs even though quite often they are kinda boring or as Marvin said “dry written”. Just spend some time on it, read it twice if necessary and you’ll get your answers ;)

    Best regards,


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