Routing

BGP Communities

BGP Communities

BGP Communities has to be one of my favorite features added to the BGP protocol. As you should know by now, BGP passes several attributes between peers that help influence the BGP …

AS-Path Filtering

AS-Path Filtering

Before we get into the how, let’s talk about the why. According to the CIDR Report, the global IPv4 routing table sits at about 525,000 routes, it has doubled in size since mid …

IP Multicast Routing Concepts

IP Multicast Routing Concepts

Can you imagine a video conference taking place on a primarily T1 based WAN? Multiple copies of the same video stream being unicast from the host to each participant. Multiple …

BGP Essentials – The Art of Path Manipulation

BGP Essentials – The Art of Path Manipulation

Most enterprise networks use BGP to peer with their Internet Service Providers if they want to be multi-homed. Many factors come into play when determining how traffic should flow, …

OSPF Graceful Shutdown

OSPF Graceful Shutdown

Striving to reach that last 9? Looking for a way to increase your uptime while still being able to do maintenance on your network? Wish you could shutdown your OSPF neighbors like …

HSRP, VRRPd, and GLBP Compared

HSRP, VRRPd, and GLBP Compared

In the world of first hop redundancy, we have plenty of choices. In order to make the right decision for your network you should know the basics regarding all three. The following …

BGP Tips! multipath load balancing

BGP Tips! multipath load balancing

Previous thoughts on load balancing BGP were that it is not a load balancing protocol and in order to achieve any sort of balanced traffic you would have to perform some sort of …

Bidirectional Forwarding Detection

Bidirectional Forwarding Detection

Bidirectional Forwarding Detection (BFD) is a UDP-based protocol that provides fast (very fast!) routing protocol independent detection of layer-3 next hop failures. BFD can be …

More BGP tricks

More BGP tricks

At times, the ‘rules of BGP’ don’t fit the needs of our productions networks. When we get into today’s production networks how often do book configurations apply? I’ll tell you one …

Policy Based Routing

Policy Based Routing

Policy based routing is the process of altering a packets path based on criteria other than the destination address, commonly referred to as ‘policy routing’. PBR (Policy …

Using /31 subnets for point-to-point interfaces

Using /31 subnets for point-to-point interfaces

Recently a “colleague”, I use that term very loosely here, was reviewing my recommendations for changes on his network. Since they’re rather tight on public IP space, and require …

Cisco MPLS VRF Configuration and Demo

Cisco MPLS VRF Configuration and Demo

A while back I asked everyone to vote on what topic they wanted to see next, and by no surprise almost every voted for MPLS VRFs. When I started working on this, I decided to take …

Route Selection

Route Selection

One of the most common questions I get concerns path selection within the router. Everyone knows (or at least they should know) that a more specific prefix will be preferred, but …

BGP Security Tips (updated)

BGP Security Tips (updated)

For some, BGP is a rather large obtrusive beast of a protocol that scares them half to death. This is not without good reason as BGP is not only the most important protocol running …

Layer 2 Ethernet transport over OpenVPN

Layer 2 Ethernet transport over OpenVPN

One of the things I used to deploy frequently at my previous position was transport for other ISPs and businesses. Since MPLS support is in its infancy on the Imagestream platform, …

Using OSPF to create unlicensed full duplex connections.

Using OSPF to create unlicensed full duplex connections.

Recently one of my clients asked me to help resolve an issue at an aggregation point on their network. They had several connections that converged onto a single unlicensed link on …

How does latency effect throughput?

How does latency effect throughput?

One of the questions I get asked several times a week by my clients is as such. While most people never associate latency with the amount of data they can send across a single TCP …