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Learning BGP Module 2 Lesson 2: Peering, Part 2 – Video

Russ White continues the discussion about BGP peering in part two of this lesson. Topics covered include: -Challenges with link-local next hop with IPv6 -How different BGP implementations handle these challenges -Promiscuous peering -Mitigating the attack surface of promiscuous peers -BGP Capabilities -Filtering before advertising/RFC 8212 You can subscribe to the Packet Pushers’ YouTube channel […]

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Learning BGP Module 2 Lesson 1: Peering Part 1 – Video

The first video in this second module of Russ White’s BGP course covers peering, including why BGP uses TCP for transport, passive and active peer, multi-hop peering, collisions, and more. Russ White is a network architect, author, and instructor. You can subscribe to the Packet Pushers’ YouTube channel for more videos as they are published. […]

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Learning BGP Module 1 Lesson 4: Intra-AS Models And Route Reflectors – Video

This lesson in Russ White’s BGP course delves into synchronization within an Autonomous System (AS) and confederation within an AS. It also discusses route reflectors, including how they prevent loops, route reflector clients, route reflector multi-path, and multi-path pros and cons. Russ White is a network architect, author, and instructor. You can subscribe to the […]

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Learning BGP Module 1 Lesson 3: How BGP Really Converges – Video

This lesson in Russ White’s BGP course gets into withdrawing a route, MRAI time, implicit withdraws, BGP Hunt, graceful restart, and other topics. Russ White is a network architect, author, and instructor. You can subscribe to the Packet Pushers’ YouTube channel for more videos as they are published. It’s a diverse a mix of content […]

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Hedge 129: Open Source Mentoring

Mentoring is a topic we return to time and again—because it’s one of the most important things we can talk about in terms of building your people skills, your knowledge, and your career. On this episode of the Hedge, Guedis Cardenas joins Tom Ammon and Russ White to talk about open source mentoring. We discuss how this is different than “regular” mentoring, and how it’s the same. Join us as we talk about one of the most important career and personal growth things you can do.

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BGP Policy (Part 7)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

In this post—the last post in this series—I’m going to cover do not transit options from the perspective of AS65001 in the following network—

There are cases where an operator does not traffic to be forwarded to them through some specific AS, whether directly connected or multiple hops away. For instance, AS65001 and AS65005 might be operated by companies in politically unfriendly nations. In this case, AS65001 may be legally required to reject traffic that has passed through the nation in which AS65005 is located. There are at least three mechanisms in BGP that are used, in different situations, to enforce this kind of policy.

Do Not Advertise Communities (Provider Specific)

Many providers supply communities a customer can use to block the advertisement of their routes to a particular AS. For instance, if Continue reading

Live Training: How Routers Really Work

On the 27th of May, I’ll be teaching a three-hour course called How Routers Really Work? From the course description:

This training will peer into the internal components of a router, starting with an explanation of how a router switches packets. This walk through of a switching path, in turn, will be used as a foundation for explaining the components of a router, including the various tables used to build forwarding tables and the software components used to build these tables.

Sign up here.

Hedge 128: Network Engineering at College

Have you ever thought about getting a college degree in computer networking? What are the tradeoffs between this and getting a certification? What is the state of network engineering at colleges—what do current students in network engineering programs think about their programs, and what they wish was there that isn’t? Rick Graziani joins Tom Ammon and Russ White in a broad ranging discussion on network engineering and college. Rick teaches network engineering full time in the Valley.

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BGP Policy (Part 6)

At the most basic level, there are only three BGP policies: pushing traffic through a specific exit point; pulling traffic through a specific entry point; preventing a remote AS (more than one AS hop away) from transiting your AS to reach a specific destination. In this series I’m going to discuss different reasons for these kinds of policies, and different ways to implement them in interdomain BGP.

In this post I’m going to cover local preference via communities, longer prefix match, and conditional advertisement from the perspective of AS65001 in the following network—

Communities an Local Preference
As noted above, MED is the tool “designed into” BGP for selecting an entrance point into the local AS for specific reachable destinations. MED is not very effective, however, because a route’s preference will always win over MED, and because it is not carried between autonomous systems.
Some operators provide an alternate for MED in the form of communities that set a route’s preference within the AS. For instance, assume 100::/64 is geographically closer to the [65001,65003] link than either of the [65001,65002] links, so AS65001 would prefer traffic destined to 100::/64 enter through AS65003.
In this case, AS65001 can advertise 100::/64 with Continue reading

Learning BGP Module 1 Lesson 2: How BGP Builds Loop-Free Paths – Video

Russ White’s BGP series continues with a discussion of building loop-free paths with the Border Gateway Protocol (BGP). Topics include AS (Autonomous System) paths, loop prevention, why loop checks are inbound, and more on IBGP and EBGP. Russ White is a network architect, author, and instructor. You can subscribe to the Packet Pushers’ YouTube channel […]

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Learning BGP Module 1 Lesson 1: Why BGP? – Video

Russ White kicks off a ten-video series on the Border Gateway Protocol (BGP). The series is divided into two modules, with short lessons within each module. This first video covers a brief history of BGP and then gets into the purpose of BPG, reachability vs. a route, Autonomous System (AS) rules, problems that BGP solves, […]

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