Friday, February 28, 2020

My DevNet Journey

Its update time.

Lets see where we are with things so far then...
  • Get it set up.  <<DONE
  • Install Visual Studio Code.  <<DONE
  • Link to my Github profile (?) page(?) whatever...<<DONE
  • Work through the Visual Studio Code Python tutorial  <<TO DO
  • Make Cisco DevNet my homepage. <<DONE
  • Work through the Programming Fundamentals course. <<ON GOING
  • Work through the Python Fundamentals course. <<TO DO
  • Move on to the DevNet sandbox environments and have a play there.  <<TO DO
  • Check out NAPALM  <<TO DO
  • Check out Netmiko  <<TO DO

My main focus has been working through the Programming Fundementals video course on DevNet

I feel I'm making steady progress but given this is a side project for me I doubt I'm going to make the DevNet 500.

I'll look at posting some further stuff on how I set up the various bits above shortly.

See you soon.

Tuesday, February 11, 2020

Stop Starting...

One of the things I'm struggling with as I attempt to get into network automation and programming is the huge volume of information.

There's DevNet, all the Cisco YouTube channels, udemy courses, cbtnuggets, Cisco press back catalogue, blogs, twitter, Facebook groups, webex teams, the list goes on and on.

I've found that I've been utterly daunted by just how much information is out there.

I spotted a quote on twitter just yesterday though -

'you must build an actual project '  @wellpaidgeek

- which pretty much summed me up.

I've spent so much time researching that I've been unable to see where to start. I look at one area and it sends me on to another, and another, and another. Before you know it I've watched 4 YouTube videos and read various blogs and not actually done anything!

So today marks my first actual steps.

I've got my new laptop due for delivery any time now. First tasks are:

  • Get it set up.
  • Install Visual Studio Code.
  • Link to my Github profile (?) page(?) whatever...
  • Work through the Visual Studio Code Python tutorial
  • Make Cisco DevNet my homepage.
  • Work through the Programming Fundamentals course.
  • Work through the Python Fundamentals course.
  • Move on to the DevNet sandbox environments and have a play there.
  • Check out NAPALM
  • Check out Netmiko

Thats all well and good but I've not actually 'done' anything even if I manage to clear that lot any time soon...

As result a simple task I'm going to look at will be :

  • A simple Python script to take pre and post change snapshots of the kit I work on. 
  • Next, develop it so I can split out specific tasks based on the type of device I'm making a change on.
  • Next, add a Diff process to compare the before and after state of my changed devices.
  • Further down the line I want to be able to look at the active connections at any one time and run a comparison for before and after my change.
  • Next, lets take all that detail and store it in a central location to be reviewed at a later date if needs be. 
  • Those are all read only tasks so I guess at some point I'll be looking to run the actual change and then run all the post checks as well.
  • It would also be nice to have a basic web page our ops team can reference to check the live status of the connections on the devices I'm working.
  • The list goes on...
Now you might say 'Hey, Sparky! there's already code out there that can do that!' - well yes, that's true. But where's the fun in copying some one else's work? what would I learn?

Today is the day I stop starting and simply start doing.

Wish me luck!






Thursday, February 6, 2020

Cisco Live 2020 - Barcelona

I was able to attend Cisco Live 2020 in Barcelona this year and it was EPIC!

It's the first time I've been to Cisco Live and had no idea what to expect. I thought I'd make a few notes on my experience with the view of keeping a list of reminders in the event that I get to go again.

In no particular order:

  • Wear comfy shoes, I was walking at least 12km each day!
  • Don't worry about the schedule - it is not possible to do everything you might want to do so pick out your 'must do's' then us the app to bookmark anything else of interest
  • Download and use the app - Cisco Events - about 2-3 days before the event the Cisco Live event was added and I could login in using my Cisco account and access my schedule (that I had already started to fill up online)
  • Make time for the World of Solutions hall and the The Hub / DevNet halls - its not all break out sessions. 
  • Get to the Walk-in Labs early, find out what time it opens and get there before 9am - I found that after my 9am talks I'd get to the Walk in Lab area at around 9:30 and all the seats were full and there was a massive queue.
  • Same for Capture the Flag - it fills up quick so get there early or go there late in the day
  • The food was awesome, everything was free (meals, sandwich bags, tea, coffee, fizzy drinks) and breakfast was also available via pastries and muffins!
  • Get Social - Follow @CiscoLiveEurope and monitor #CLEUR for updates and news
  • Drop  in on sessions that have already started, if you spot a session that you hadn't seen on the schedule before you arrived don't think twice about rocking up and standing in the corner. I did this a few times and found there was always a spare chair. People's plans change and I never had trouble find a chair even on the ones I hadn't register for prior.
Would I go again? ABSOLUTELY! I learnt more in one week at Cisco Live than I had in previous roles going back years. In your day to day role you will no doubt have a set number of duties and its really easy to forget that there's more to networking than the bit you do. Cisco Live opened my eyes to whats out there and what's coming in the future and it was amazing.

I also loved the fact that I was with like minded people who were enthusiastic and that got me really engaged and excited about the possibilities on my return to work.

I doubt I'll get to go to Amsterdam next year but I'll be sure to be planning a visit as soon as I can.

Tuesday, January 14, 2020

New Year - New Posts!

How long is it since I've posted!

A lot has happened since my CCDP Arch posts. I passed my CCDP - Yey! I've re-certified all my Cisco certs with a last gasp effort last autumn whilst the counter to the 4th November (expiry day) was counting down.

It took me 3 attempts to clear the CCNP - ROUTE , with a week to go, which brings my routing up to date given my last routing exam was the BSCI.

2020 marks my first time at Cisco Live as well. Really looking forward to Barcelona on the 27th and I'll be adding a few posts around my experiences as a first timer.

Finally I'm intending on picking up the ENCOR study material and get my self prepared for the CCIE lab - eek! - Not sure if I'll clear it but what the hell, I'll pick up a load of skills on the way.

Good luck in your NetworkStudies folks!


Tuesday, March 18, 2014

CCDP - ARCH - Command Reference

This article looks to collect together the most frequent commands associated with the CCDP ARCH exam.

The point being that these are easy marks to pick up on the exam when you get a question such as 'Name the command that allows you to [insert task here]'

This list is by no means complete and I'll add further commands as I find them.

OSPF - Originate a default route in to OSPF
    #router ospf 10
        #default-information originate [always]

OSPF - On the ABR filter out all advertised routes accept those listed in the range command
Limits the size of the DB and reduces the flooding internally
    #router ospf 1
         #area 20 range 192.168.200.0 255.255.255.0

OSPF - On the ASBR filter routes sent out externally to those explicitly listed.
    #router ospf 20
         #summary address [prefix] [mask]

OSPF - Tune the OSPF hello timer interval for faster convergence
    #interface f0/0
        #ip ospf hello-interval [seconds]

OSPF - tune SPF timers to increase efficiency
    #conf t
          #timers throttle spf [spf-start] [spf-hold] [spf-max-wait]

OSPF - Increase the reference bandwidth to factor in high speed link such as 10GB ethernet, do this across all links for consistency
    #router ospf 20
          #auto-cost reference-bandwidth 10000 (for 10Gb ethernet links)

EIGRP - Originate a default route in to EIGRP
    #conf t
         #ip default-network [network ip]

EIGRP - configure unequal-cost load balancing
    #router eigrp 1
       #variance 2

BGP -configure neighbor as a Client of the route reflector
    #router bgp 65123
        #neighboor 1.1.1.1 route-reflector-client

IPv6 - enable IPv6 routing for use with RIPng, EIGRP for Ipv, OSPFv3 etc
    #conf t
         #ip v6 unicast-routing

IPv6 - Define a base prefix to use for addressing:
  #conf t
       #ipv6 general-prefix [prefix]

CEF - Eliminate CEF Polarisation where one redundant link ends up being preferred to the other
    #conf t
         #mls ip cef load-sharing

EtherChannel - Use this to ensure all links within an Etherchannel bundle are utilised effectiviely
    #conf t
        #port-channel load-balance src-dst-port

FlexLinks  - Configure a port to act as a resilient backup for FlexLinks. Configure this on the primary link.
    #interface f0/10
       #switchport backup-interface [interface id]

Friday, March 7, 2014

CCDP - ARCH - Well Known Multicast Addresses

In the CCDP ARCH exam there are numerous refereences to Multicast addresses.

This post is to simply catalogue those that are specifically refered to in the various reading materials I've covered.

Address Scope:
  • 224.0.0.0 /4 - Class D reservation
Address type:
  • 224.0.0.0 to 224.0.0.255 - assigned by IANA for services (detailed below)
  • 224.0.1.0 to 224.0.1.255 - Control Block - assigned by IANA for traffic crossing public networks e.g.- NTP 224.0.1.1
  •  224.0.2.0 to 224.0.255.255 - AD-HOC block assigned by IANA for addresses that don't fit the above ranges
  • 224.3.0.0 to 224.4.255.255 - AD-HOC block assigned by IANA for addresses that don't fit the above ranges
  • 233.252.0.0 to 233.255.255.255-  AD-HOC block assigned by IANA for addresses that don't fit the above ranges
  • 232.0.0.0 255.0.0.0 - Source-Specfic Multicast Addresses
  • 233.0.0.0 255.0.0.0 - GLOP addresses - Originally experimental now publically assigned addresses for use by ISPs and any organisation want to ublich content over Multicast
  • 234.0.0.0 255.0.0.0 - Uni-cast Prefix addresses
  • 239.0.0.0 255.0.0.0 - Administratively scoped IPv4 addresses, locally assigned, not globally unique
Well Known Addresses:


  • 224.0.0.1 The All Hosts multicast group addresses all hosts on the same network segment.

  • 224.0.0.2 The All Routers multicast group addresses all routers on the same network segment.

  • 224.0.0.5 The Open Shortest Path First (OSPF) All OSPF Routers address is used to send Hello packets to all OSPF routers on a network segment.

  • 224.0.0.6 The OSPF All Designated Routers ""(DR)"" address is used to send OSPF routing information to designated routers on a network segment.

  • 224.0.0.9 The Routing Information Protocol (RIP) version 2 group address is used to send routing information to all RIP2-aware routers on a network segment.

  • 224.0.0.10 The Enhanced Interior Gateway Routing Protocol (EIGRP) group address is used to send routing information to all EIGRP routers on a network segment.

  • 224.0.0.13 Protocol Independent Multicast (PIM) Version 2

  • 224.0.0.18 Virtual Router Redundancy Protocol (VRRP)

  • 224.0.0.19 - 21 IS-IS over IP

  • 224.0.0.22 Internet Group Management Protocol (IGMP) version 3

  • 224.0.0.102 Hot Standby Router Protocol version 2 (HSRPv2) / Gateway Load Balancing Protocol (GLBP)

  • 224.0.1.1 Network Time Protocol clients listen on this address for protocol messages when operating in multicast mode.

  • 224.0.1.39 The Cisco multicast router AUTO-RP-ANNOUNCE address is used by RP mapping agents to listen for candidate announcements.

  • 224.0.1.40 The Cisco multicast router AUTO-RP-DISCOVERY address is the destination address for messages from the RP mapping agent to discover candidates.

  • 224.0.1.41 H.323 Gatekeeper discovery address

  • 239.255.255.250 Simple Service Discovery Protocol address




  • Tuesday, January 14, 2014

    CCDP - ARCH - Spark's rules for Design

    Last year I passed the CCDA and I'm presently studying for the ARCH exam and during my studies I've noticed common themes in how to approach network design.

    In general I've found that it comes down to making the best of what you've got (unless you're Google and simply commission your own hardware and build your very own private internet - coming to home near you soon...)

    Based on that I've noted the following observations during my studies:

    • Divide and Conquer! - Large flat networks are generally a bad idea, they propagate all the broadcast/multicast traffic to all hosts, make poor use of available network resourse (bandwidth, increase work on routers/firewalls etc),  are difficult to scale, increase the impact of a network event across the environment. Where possible segment it. For example:
      • OSPF - Make use of backbone routers in Area 0 and then use different areas to limit the propagation of Link State Advertisiements. In doing this you reduce the amount bandwidth used up by the OSPF process, you reduce the about of processing load on the routers within each area and the LSA's are limited to each area (reducing the content of the Routing Table). Originate the Default Route from Area 0 and where possible make use of Stub, Totally Stubby and Not-So-Stubby-Areas to reduce LSA/Route propagation.
      • Campus Design - Make good use of Hierarchical designs with a Core, Distribution/ Aggregation, Access Layers. These scale well, limits broadcast domains and make troubleshooting more logical
      • IP Address Assignment - Use contiguous networks and avoid any discontiguous subnets. Contiguous subnets makes address assignment easier (more efficient allocation of address space), troubleshooting easier, you can trace through the network easier, allows for efficient route summarisation and redistribution.
    • Summarise it! - Expanding on the previous point, when advertising routes, where possible advertise summary routes for destinations in a given area/zone. By advertising a summarised route you are reducing the size of routing tables on upstream routers and you then limit the impact of route flaps within the network. If a single link goes down then a route that is advertised as a /30 would need removing from all routers that have a route for this network. If the failed link falls under a /24 route then the upstream routers don't observe the link flap and do not have to re-calculate the shortest path which inturn means that resources on upstream routers are not utlised unneccesarily.
    • Keep It Simple! - At the dead of night that on call network engineer will not thank you for building that convoluted network that makes use of lesser know commands just because it's fancy. Always consider how difficult troubleshooting the proposed solution will be and keep it simple. For example:
      • Avoid OSPF virtual links - an network outage in the transit area could cut off the remote area to area 0
      • Keep access lists consistent - Agree on a naming convention for access lists, object-groups, hosts. Agree on how an access list will be named and how it will be constructed and stick to it. Being consistent will make for a cleaner running-config and will make reading it easier which in turn should make troubleshooting easier
    Now, the point of the rules above is to apply each rule as measure of how to approach exam questions. For any given question can the rules above be applied and the correct answer revealed? (Of course you should know your stuff when it comes to sitting an exam but sometimes you get blind sided by a badly worded question)

    Remember to be methodical and ultimately consider What Would Cisco Do...?

    Wednesday, December 11, 2013

    CCDP - ARCH - Route filtering

    Filter routes inbound to a router via a 'distribute-list' cmd to prevent inbound rutes from being learned.

    Filter routes outbound to a neighbour via a 'redistribute [protocol] [process number] route-map FILTER' cmd and a deny statement on the FILTER route-map to stop routes from being advertised towards a neighbour.

    CCDP - ARCH - Migrate Routing Protocols By Manipulating the AD

    High level steps to move from one RP to another by manipulating the AD:
    1) Configure the new RP and manually set the AD to be Higher (and therefore less preferred) than the current RP
    2) Configure all devices as necessary and then check the topology using appropriate show commands
    3) Ensure the new RP has all the required routes in its database
    4) Either by increasing the AD on the current RP or by reducing the AD on the New RP change the AD so that the new RP is the preferred RP to use
    5) Use show commands to ensure that the new RP is populating the routing table correctly (there shouldn't be any routes learned via the old protocol - if there are some then troubleshoot accordingly)
    6) Remove the old RP from the routers
    7) Move to normal running

    Thursday, November 14, 2013

    CCDP - ARCH - UDLD (UniDirectional Link Detection):


    • Used where there are fibre links between switches (but can also be applied to Copper interfaces)
    • Interface could be seen as Up/Up but due to a mismatch on the tx/rx pairs the comms become unidirectional 
    • UDLD Normal mode error-disabled the end that detected the unidirectional state - default mode
    • UDLD Agressive mode disables both ends - set it with the [agressive] switch
    • Uses 15 sec hello timer
    • Can be applied globally or on the interface