IPv6 Summarization

Summarizing IPv6 addresses is quite similar to the summarization of IPv4 addresses. The only real differences are:

• IPv6 is 128bit while IPv4 only has 32 bits
• IPv6 is written in HEX while IPv4 is written in decimal

If we take those two differences into account the summarization is the same.

Book Review: The Complete Cisco VPN Configuration Guide

Ok this is my first book review, so please be kind with me

Even though Im not so much into security, I recently bought The Complete Cisco VPN Configuration Guide (written by Richard Deal) cause we got quite a number of VPN connections at work and I wanted to have something like a reference book for VPN.

Preserve the integrity of the certification process

Actually I was thinking to not blog anything about the which-hunt that was going on against Ethan Banks other Blogs wrote enought about it. But during the reads I found a link to an interview with Cisco and Vue on what they are planing to do against cheats during the exams and in the preparation for the exams.

PPP and host routes

Maybe some of you did configure a ppp connection and wondered about the new host route in the routing table after the PPP connection went alive. This is nothing to worry about since its a normal behavior of PPP and IPCP and also allows the routers to not even share the same subnet to get the line up and running.
Given the following diagram with a simple back to back connection between R4 and R5. Both interfaces have a different subnet.

BGP Path Attributes I

The BGP path attributes are the characteristics for all BGP advertised routes. Additionally to the necessary informations to perform basic routing , the path attributes allow BGP to set routing policies and advertise them. Each attribute is a member of one of the following categories:

• Well-known mandatory – This attribute has to be known and implemented by all BGP implementations
• Well-known discretionary – This attribute has to be known by all BGP implementations, but does not have to be sent in an update message.
• Optional transitive – This attribute does not have to be known by all BGP implementations but the BGP prozess has to accept the path within the attribute is found and forward it to other BGP peers, even though the BGP process doesnt know the attribute.
• Optional non-transitive – An update with an attribute from this category can be ignored. The router does not have to advertise this route nor the path to its peers.

All examples in this document will use the following diagram

Sign of Life

Hi all
I dont know if there are any regular readers but I wanted to say that Im still around even though I did not put up a new article since more then a week. Im just a bit busy and since Im first writing or rewriting my documentation before I translate it and put it up here, it takes some more time to have a new article ready.

To give you a forecast on what Im currently planing to write/rewrite (no fix order):

• Lock and Key Security
• BGP Path Attributes
• IPSec Overview
• Virtual Tunnel Interfaces
• Testing Connectivity with TCL script and macros
• OSPF LSA types and areas
• IPv6 summarization

Hope there’s something interesting for you

BGP Aggregate Addresses

With BGP you have two different ways to create aggregate Routes:

• Aggregate addresses with static routes
• The command aggregate-address

The whole document will be using the following configuration:

The examples will mainly use the loopback addresses from R1