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Is RIP layer 3 protocol or layer 7 protocol?

Posted on 2001-09-13
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I think the routing protocols are layer 3 protocol,but RIP has PORT 520 in layer 4 ,Only upper protocols can have PORT number.
i am confused and please help me!
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Question by:bitsnake
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bsadlick earned 100 total points
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The routing application operates at higher than layer 3; it controls layer 3 forwarding. UDP port 520 is open for RIP updates to the routing daemon. Remember that routing is a computer program, just like most others.
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by:mikecr
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Yes, routing is basically software that looks at the source and destination address of a packet and forwards the packet accordingly. Try not to use ports for a distinction as I can send any information down almost any port as long as both ends will communicate on the same port.
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by:bitsnake
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so all the routing protocol rip,igrp,eigrp are layer 7 protocols?in the ccna 2.0's student book,rip is considered as layer 7 protocols on the other hand igrp is not mentioned.

is the rip different from other routing protocol?is rip special?i couldn't find igrp's port number less than 1024  in layer 4.

Is rip SPECIAL?
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by:mikecr
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Yes again. Routing protocols are software applications, making them layer 7, but they work at layer 3 of the OSI model. There is nothing special about RIP compared to other protocols. RIP is actually a lower end routing protocol compared to EIGRP and OSPF.

This will help you to understand them.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios11/cbook/ciproute.htm
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by:scraig84
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Hmmm, I actually would say that not every routing protocol goes above layer 4.  IGRP (and consequently EIGRP) and EGP for example have their own IP type values, which means they are sitting directly above IP and do not use UDP or TCP services.  This is not to say that they carry out the functions of a layer 4 protocol.  Its kind of hairy.  I would agree that all routing processes are of an application nature.  However, when I think of an application protocol, I immediately think "anything above layer 4", since the top 3 layers are traditionally application based and named the application layers.  This means that an application can be "socket based".  However, there is no socket if there are no layer 4 port values to be used.

What bitsnake is finding is interesting, since traditionally, books put all routing protocols as a sub-section of layer 3, since they control layer 3 forwarding.  However, technically they are all application based to one degree or another, although they fit into different layers above layer 3.
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by:bsadlick
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I think that we are all trying to say the same thing. Routing protocols are applications that may utilize the upper layers, but are used to control layer 3 forwarding.

IGRP and EGP may not use TCP or UDP, but if the data that they are trading is contained within the data portion of the IP datagram, then technically I would say that they are using layer 4 to transport routing information.
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by:scraig84
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Agreed.  My point was that in order to say "they are all layer 7" with or without layers 5 and 6 being used, I think it needs to be above layer 4 first.  However, you could easily call that being picky :).
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by:SteveJ
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Wait a minute . . .  follow this link and then tell me RIP is an application.

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/osi_prot.htm

I think that part of the problem in trying to pigeon hole things like routing protocols into the OSI model is the underlying assumption that _ IF_ TCP/IP or IP addressing is involved _THEN_ the process will fit neatly into the OSI model definition. Think about SNMP. It's a little easier to see how this fits into the model . . . there's a presentation layer, albeit crude, a session control layer (HELO, QUIT) . . . but RIP and EIGRP don't fit neatly into the model. It's an interesting if only academic question. Like mikecr said, selection of a transport and derivatively a socket doesn't imply an application.

Good luck on your exam.

Steve
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