Understanding Third-Party Next-Hop
Abstract
This publication briefly covers the use of 3rd party next-hops in OSPF, RIP, EIGRP and BGP routing protocols. Common concepts are introduced and protocol-specific implementations are discussed. Basic understanding of the routing protocol function is required before reading this blog post.
Overview
Third-party next-hop concept appears only to distance vector protocol, or in the parts of the link-state protocols that exhibit distance-vector behavior. The idea is that a distance-vector update carries explicit next-hop value, which is used by receiving side, as opposed to the “implicit” next-hop calculated as the sending router’s address – the source address in the IP header carrying the routing update. Such “explicit” next-hop is called “third-party” next-hop IP address, allowing for pointing to a different next-hop, other than advertising router. Intitively, this is only possible if the advertising and receiving router are on a shared segment, but the “shared segment” concept could be generalized and abstracted. Every popular distance-vector protocols support third party next-hop – RIPv2, EIGRP, OSPF and BGP all carry explicit next-hop value. Look at the figure below – it illustrates the situation where two different distance-vector protocols are running on the shared segment, but none of them runs on all routers attached to the segment. The protocols “overlap” at a “pivotal” router and redistribution is used to provide inter-protocol route exchange.
Tags: bgp, CCDE, ccie, eigrp, ospf, rip, third-party next-hop
Are you a CCNP or CCIE student looking to challenge your perfect knowledge of Catalyst switchport commands?
Take the latest SWITCH Command Recall exam by clicking the link below. Good luck – and let us know how you scored in the comments area of this post.
Remember to read, AND TYPE, very carefully! I failed my first attempt due to just plain sloppiness. 
For success designing and implementing Cisco Wireless solutions, a CCNA Wireless student needs to be familiar with the options for various wireless topologies. Two were defined by the 802.11 committees, while others were made possible thanks to excellent developments by wireless vendors like Cisco Systems.
The 802.11 Topologies
Ad Hoc Mode
While not popular, it is possible to have wireless devices communicate directly with no central device managing the communications. This is called the Ad Hoc network topology and is one of the two topologies defined by the 802.11 committees. In the Ad Hoc type topology, one device sets a group name and radio parameters, and another device uses this information to connect to the wireless network.
This type of wireless network topology is referred to as an Independent Basic Service Set (IBSS). This is easy to remember as we know the devices are working independently of an access point (AP).
Network Infrastructure Mode
When an access point is used to create the network, the official term is network infrastructure mode for the network. There is a Basic Service Set (BSS) setup that uses a single access point, or the Extended Service Set (ESS) that uses multiple access points in order to extend the reach of the wireless network.
One of the frequent questions I hear regarding L3VPNs, is regarding the bottom VPN label. In this article, we will focus on the control plane that provides both the VPN and transit labels, and then look at the data plane that results because of those labels.
In the topology, there are 2 customer sites (bottom right, and bottom left). The BGP, VRFs, Redistribution, etc are all configured to allow us to focus on the control and data plane. Lets begin by verifying that R1 is sourcing the network, 1.1.1.1/32.
A debug verifies that R1 is sending the updates for 1.1.1.1 to R2.
In this blog post we’re going to discuss the fundamental logic of how MPLS tunnels allow applications such as L2VPN & L3VPN to work, and how MPLS tunnels enable Service Providers to run what is known as the “BGP Free Core”. In a nutshell, MPLS tunnels allow traffic to transit over devices that have no knowledge of the traffic’s final destination, similar to how GRE tunnels and site-to-site IPsec VPN tunnels work. To accomplish this, MPLS tunnels use a combination of IGP learned information, BGP learned information, and MPLS labels.
We wanted to provide our students with advance notification of some upcoming online classes here at INE. While we hope to see many students in the actual live events, on-demand versions will indeed be made available the week following the live, online version.
Join the INE Experts Online in September and October
September 13 – 17th, 2010 CCNA Wireless 5-Day Bootcamp
September 15 – 17th, 2010 Security for CCIE R&S Candidates 3-Day Bootcamp
September 29 – Oct 1, 2010 IPv4/IPv6 Multicast 3-Day Bootcamp
October 4 – 9th, 2010 Online 6-Day CCIE R&S Bootcamp with K. Barker and A. Sequeira
Our BGP class is coming up! This class is for learners who are pursuing the CCIP track, or simply want to really master BGP. I have been working through the slides, examples and demos that we’ll use in class, and it is going to be excellent. 
If you can’t make the live event, we are recording it, so it will be available as a class on demand, after the live event. More information, can be found by clicking here.
One of the common questions that comes up is “Why does the router choose THAT route?
We all know, (or at least after reading the list below, we will know), that BGP uses the following order, to determine the “best” path.
So now for the question. Take a look at the partial output of the show command below: Continue Reading
For each new CCIE Testimonial we are extending the seven years of success sale! Share your INE success story and congratulations to the following new CCIE Testimonials who have extended the sale thus far!
Thomas Fischer, CCIE #26636 – Routing & Switching
I am proud to let you know, that I passed my CCIE R&S Lab in Brussels on Aug. 5th. This was my second attempt. I want to express my deepest appreciation for your Products. I am a self-paced student, using Vol1 (*****), Vol2 (****) and Vol4 (***). Thanks INE, it feels so good to have a social life again
Matthew Ayre, CCIE #26654 – Service Provider
Big shout out for INE and their OEQ / lab preparation resources! I just cleared service provider on second attempt finishing about an hour and a half early. Was ~7% of passing the first time using INE 1 & 2 as my primary material then just drilled down on the finer details reading theory. The workbooks really developed the speed and confidence required to beat the exam!
Prateek Madaan, CCIE #26772 – Security
Had been a long and tough journey. Would really like to thank INE from the Core of my heart for facilitating in imparting the skills required not to just pass the exam but to DESERVE it as well…
There are many workbooks available which I prepared along with INE , do not want to name or list any one of them…or make any comparisons…But in comparisons INEs Security Workbooks may sound tough as compared to others BUT once you go through these workbooks is when you actually feel DESERVED the tag rather than just passing it.. Each of these workbooks and the tasks test each and every technology in detail and till the dead end….
In my last attempt on Version 2 I was deprived of the number by 1%, still followed and trusted INE workbooks and finally it helped….Today I am more happy not to procure the number but to actually have the feeling of confidence that ‘YES this time I deserve to be a CCIE’ and all due to the exhaustive INE workbooks….
Update!
Olusegun Olurotimi Medeyinlo, CCIE #26683 – Routing & Switching
I the Passed the CCIE R&S lab in Brussels on my Second attempt. I’d like to thank the instructors at INE for their excellent workbooks and blogs. Special thanks to Keith Barker for his encouragement and advice.
Now, I have my own CCIE number #22683.
Congratulations to everyone who passed the CCIE Lab Exam. Our instructors, authors, and staff have been committed to helping you pass your exam for the past seven years and we will continue to make your exam our number one priority. Only at INE.
Tags: ccie, Shared Success
Many businesses globally – large and small alike – have been converting calls from routing over traditional PSTN carrier trunks – such as E1 & T1 PRI or CAS – to much lower cost, yet still high performance, SIP ITSP (Internet Telephony Service Provider) trunks for years now. INE is no different than your business with regard to this – we have been using SIP trunks in lieu some traditional PSTN calling for years now as well. In fact, in response to a US Federal Communications Commission sub-commitee’s exploration on “PSTN Evolution” in December 2009, a representative from the US carrier AT&T described the traditional circuit-switched PSTN as “relics of a by-gone era”, and said that “Due to technological advances, changes in consumer preference, and market forces, the question is when, not if, POTS service and the PSTN over which it is provided will become obsolete” – source: Reuters [emphasis mine].
The challenge however, becomes that every SIP ITSP carrier has a slightly different way of implementing these sorts of trunks, and each has different provider network equipment that you, the customer, must connect to, and interoperate (properly) with. If you are a large national or multinational business, you may for instance sometimes even connect to two or three different types of provider network equipment, between possibly having multiple contracts with multiple carriers, and even sometimes having to deal with different provider equipment within a single carrier’s network.
Tags: call-manager, CCIE Voice, cisco unified border element, cisco voice, CUBE, ip-phone, sip, sip normalization, telephony, unified communications, unified communications manager, voip phone
As you may have noticed, INE does a wide variety of training in the Cisco space. This blog post goes out to all those folks who have recently begun their Cisco training.
This month we delivered new live classes on CCNA and CCNP. We are excited for and encourage our students at every level in their journey. In that light, we have gathered a collection of Videos Answers, targeted at the CCNA level, with a few topics leaking into security and CCNP. These videos were primarily created as quick (under 10 minutes each) Video Answers to questions that various learners have had.
Take a look at the list of topics, and if there are 1 or 2 you feel you would benefit from, feel free to enjoy them.
Here are a few of the topics (in no particular order):
- How the network statement really works in IOS
- Setting up SSH
- Initial commands for sanity sake
- NAT with overload
- Router on a stick
- VRFs Continue Reading
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