Cisco Intro Chapter 14 - BGP

Daniel333

I just finished reading chapter 14 here, and they make a huge point of knowing what type of routing protocol, RIP, IGRP, IS-IS and EIGRP are, but they never state (unless I missed it) what type BGP is? I googled it, and didnt' find much.

Any ideas?

georgemc

I didn't think BGP was covered on the CCNA exam...but

BGP(Border Gateway Protocol) is an external routing protocol, and to quote "Routing TCP/IP Vol. II, 1st Ed", which covers external routing protocols. Chapter 2, page 90 states; "BGP is a distance vector protocol in that each BGP node relies on downstream neighbors to pass along routes..."

laup

BGP is not covered in CCNA, it is used to connect between AS's.

nitishh

Just as georgemc put it BGP is DVP . It is the a wonderful protocol . Once you get to know all about it . It is very flexible and do wonders at the same time can make your life a living hell . There are some good white papers on cisco website on BGP and ofcourse there is the book by sam halabi which is great . In theory you can use any protocol you want in your network there is no stopping if you want u can use BGP inside your network .

borumas

For the CCNA I think the only thing you need to know about BGP is that it is usually used only for ISP to ISP links and that it works at layer 2. I can't remember if I had a question on the INTRO about it or not, or maybe I'm remembering some study prep question I took.

nitishh

BGP is a routing protocol it is not layer 2 its layer 3 . BGP is used to connect between AS . So say if i wanted to connect with an ISP and exchange routing information then the prefered method (routing protocol) would be BGP . Two ways to run BGP is IBGP and EBGP . IBGP is internal bgp and EBGP is external

thanks

Nitish

borumas

BGP is a routing protocol it is not layer 2 its layer 3 . BGP is used to connect between AS . So say if i wanted to connect with an ISP and exchange routing information then the prefered method (routing protocol) would be BGP . Two ways to run BGP is IBGP and EBGP . IBGP is internal bgp and EBGP is external

Hmm, I remember reading in a prep question that WAN traffic only operated at layer 1 and 2 (and BGP passing WAN traffic), maybe the question was wrong or misleading, of course I couldn't find any info online if it is layer 2 or 3 but I'll take a CCIE's word for it.


....dug up the question that got me confused on BGP:
Which two statements correctly characterize Wide Area Networks (WANs)? (Choose two)
HDLC, X.25 and PPP are examples of WAN protocols.
WAN technologies function at the two lowest layers of the OSI reference model.

cambei

WAN Protocols do run at Layers 1 and 2, but that doesn't mean higher layers cannot run over WAN links.

BGP is a layer 3 protocol and could be used within a LAN, it doesn't matter as long as IP is supported on the link.

Someone correct me if I am wrong.

nitishh

on the mark Cambei


Every layer depends on each other to complete their task . BGp is a layer 3 protocol and does not matter what your wan/link is if you have ip connection BGP will work. The other thing to remember about routing protocol is that they do not carry data traffic all they do is carry routing info . How to get to a certain network ? what is the next hop? what is the metric of the next hop?. when a packet comes to a router the router will look up the routing table which is populated by the routing protocol and use that info to send the packet

mikej412

But for the CCNA, the most you may need to know about Exterior Gateway Routing Protocols may be how to spell BGP and EGP I think it was covered in the CCNA Network Academy Courseware so that you would know what those "other things" in the Administrative Distance Table were and to lay the foundation for later CCNP studies.

BGP is the "routing protocol of the Internet" and the biggest reason you won't see it used as an IGP is its slow convergence time. Out on the internet, some interface is probably flapping somewhere -- and BGPs slow convergence (and other features) is a benefit to the entire Internet community.

For IGPs -- the quest has been for the best convergence time -- that's why the link state protocols (and the "hybrid EIGRP") have won over the distance vector protocols (RIP and IGRP). OSPF and ISIS do have the capability for sub-second convergence -- but you will not be tested on that in the CCNA either.

At the CCNA level, when we offer you the blue pill or the red pill -- they are really both just M&Ms. And they both probably fell on the floor, which is why we didn't eat them.

borumas

Ok, those post clear it up for me, thanks for the info.