The ICMP Redirect

You will not find this very often though, you may come across a network where there are two routers on the same broadcast segment, each responsible for different networks. So how do you get your hosts to know which gateway should they use? You could setup two default gateways – both Windows and Linux allow that. However, you could also rely on ICMP Redirects. In this blog, I will show you what ICMP redirect is and in what circumstances it can be useful. I will be working on the following topology: The routing table on HOST1 and ROUTER1 look like…

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ISP Network Design

I have been reading recently quite a bit in regards to ISP core network designs and quickly realised that ISP network design is a serious undertaking indeed. In this blog, I wanted to add some structure to notes I have been taking for the past few days on this topic.

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BGP Attributes and BGP Path Selection

In this blog I will briefly review the BGP path selection algorithm used when deciding which BGP routes to install in the routing table. Though before doing so, I ought to review first the BGP attributes. BGP ATTRIBUTES TYPES Firstly, we classify BGP attributes based on whether or not they should be supported within a specific vendor BGP implementation. Well-Known BGP attributes are supported in all BGP implementation regardless the vendor. Depending on whether or not these are sent with BGP Updates, we further classify them into: Mandatory attributes – these must be present in every single update where NLRIs…

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