Blog POSTS

TI-LFA FTW!

This quirk provides a brief introduction to Segment Routing followed by an in-depth look at LFA technologies – focusing on how TI-LFA can use Segment Routing to provide complete coverage.

It’s not easy building GRE

This quirk looks at an interesting scenario whereby a multi-national ISP builds a GRE tunnel over a Transit provider as a backup path.

Routing loop shambles

This quirk looks into the problems that can arise when using OSPF sham-links over an MPLS network when a dual-homed site is involved.

IVE ARP’d on for too long

The purpose of this blog is to highlight how different platforms respond to ARP requests and to explore some strange default operations on Juniper IVE VPN platforms. This quirk was found during a datacentre migration, during which the top-of-rack/first-hop device changed from a Cisco IOS 6500 environment to a Nexus Switching environment. The general setup…

Peering into the Future

Network automation is becoming more and more ubiquitous these days. Configuration generation is a good example of this – why spend time copy and pasting from prepared templates if a script can do it for you? This small blog introduces the first python script to be released on netquirks. The script is called PeerPal and…

The A to Zabbix of Trapping & Polling

Monitoring is one of the most crucial parts to running any network. There are many tools available to perform network monitoring, some of which are more flexible than others. This quirk looks at the Zabbix monitoring platform – more specifically, how you use combined SNMP polling and trapping triggers to monitor an IP network, based…

The Friend of my Friend is my Enemy

Imagine you’re a provider routing a PI space prefix for one of your customers. Now imagine that one of your IX peers started to advertise a more specific subnet of that customer network to you. How would and how should you forward traffic destined for that prefix? This quirk looks at just a such a…

From MPLS L3VPN to PBB-EVPN

This blog introduces PBB-EVPN over an MPLS network. But rather than just describe the technology from scratch, I have tried to structure the explanation assuming the reading is familiar with plain old MPLS L3VPN and is new to PBB and/or EVPN.

Multihoming without a PE-to-CE Dynamic Routing Protocol

This quirk looks at how a multihomed site without a CE-to-PE routing protocol, like eBGP, can run into failover problems when using a first hop redundancy protocol. The setup is as follows: The CE routers in this case are Cisco 887 routers. The WAN connections are ADSL lines. From the CE routers, PPP sessions connect to…

MPLS Management misconfiguration

There are many different ways for ISPs to manage MPLS devices like routers and firewalls that are deployed to customer sites. This quirk explores one such solution and looks at a scenario where a misconfiguration results in VRF route leaking between customers. The quirk When an ISP deploys Customer Edge (CE) devices to customers sites they might,…

Site by Site MPLS Breakout Migration

This months quirk is a bit late. I have been studying furiously and managed to pass my Deploying Cisco Service Provider Advanced Network Routing exam last week. Only two to go before I get CCNP SP. 🙂 Another plus side is that I have a tonne of study notes that I will be uploading over the next…

Asymmetric routing caused by unfiltered redistribution

This quirk demonstrates how the different administrative distances of BGP, combined with the Best Path Selection algorithm can cause asymmetric routing if redistribution isn’t done carefully. As a reminder, each blog will follow 3 sections: The quirk, the search and the work. The quirk describes the problem, the search shows how a solution was reached…

Bridging Layer 2 Across the Core

Welcome to netquirks As this is my first blog I thought I should write a bit of an introduction. This site is dedicated to looking at interesting and, as the name suggests, quirky scenarios in the world of Network Engineering. I’ve also added some of my study notes, GNS3 labs and other bits and pieces,…

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