How to Configure a BIND Server on Ubuntu

Introduction Within this article, we will configure a BIND server within Ubuntu. The advantages of having a local DNS server include: Reduced latency to DNS requests/responses Ability to add private addresses and full flexibility of zone names. Especially useful for VMware installations. It is important to note that the steps provided, are based on a quick setup. Due … Read more

What is a BGP Confederation?

Confederations By its true definition, a confederation is an organization which consists of a number of parties or groups united in an alliance or league. But what is a BGP confederation? BGP Confederation A BGP confederation is an alternative method to route reflectors, used to reduce the number of BGP peerings within a single AS. … Read more

Cisco – What is BGP ORF (Outbound Route Filtering)?

What is ORF? Outbound Route Filtering (ORF) is a Cisco proprietary feature that prevents the unnecessary exchanging of routes that are subject to inbound filtering. This, in turn, minimizes bandwidth across the links and reduces CPU cycles upon the router during the processing of the neighbor UPDATE. ORF works by the router transmitting its inbound filters … Read more

What is the BGP Path Selection Process?

BGP Path Selection Process BGP exchanges routes (prefixes) between BGP peers. Each of these announcements from a peer for a prefix is called a path. [1] The routes within these UPDATE messages are stored within the BGP Table and kept separate from the Routing Information Base (RIB). The BGP process then selects the “best” path from … Read more

Cisco IOS – BGP Soft Reconfiguration

Introduction When the BGP routing policy is amended the BGP neighbor session must be reset in order for the changes to take effect. Of course in a production environment performing a hard reset i.e clear ip bgp … ,  isn’t something that is recommended. Within this article, we will look at the various options available … Read more

What is Multicast Reverse Path Forwarding (RPF)?

Introduction Reverse path forwarding (RPF) is a technique used in modern routers for the purposes of ensuring loop-free forwarding of multicast packets in multicast routing and to help prevent IP address spoofing in unicast routing. [1] Within this article, we will look at multicast RPF, and look into why it is needed along with how it … Read more

BGP – Messages and Adjacency States

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BGP Messages Within BGP (as per RFC 1771) there are four BGP message types. They are, OPEN – Used to open a BGP communication session between peers. This is the first message sent by each side once the 3WHS is complete, and can be thought of as a HELLO. Only once each side has confirmed … Read more

Cisco IOS – How to Configure OSPF

Introduction With this article, we will look at the basic commands used within Cisco IOS to configure OSPF. Basic Configuration To initially configure OSPF, at a minimum, you must configure three things – process ID, router ID, and the network. Process ID – Defines the OSPF process ID that OSPF will run under. This is … Read more

OSPF – The Neighbor Relationship

Introduction In order for OSPF-enabled routers to exchange information, they must form an adjacency (relationship) with their neighbor. Within this article, we will look at the process and various steps involved (Figure 1). Requirements Before the OSPF router even starts to try and form an adjacency, OSPF must know/determine the following: Router ID – The … Read more

What is IGMP?

Introduction IGMP (Internet Group Management Protocol) is a Layer 3 protocol (IP protocol number 2) and is a key component (Figure 1) to IP multicast. The role of IGMP is to notify a local multicast router when a host wants to receive multicast traffic for a specific group. Figure 1 – Summary of Multicast Components. There are 3 versions … Read more