the worlds gone mad

we've lost the hope we had

Posted on 1 May 2022   13 min read

BGP MPLS-VPN Option B

carrying label information in bgp updates

The Cisco documentation about this call it Inter-AS Option B with the use case being to extend LSPs between sites over the one link. As Option B is the only MPLS-VPN method supported by Cisco SD-WAN I wanted to get a better understanding of how it works aswell as see if it could be used to extend multi-VRF prefixes between edge routers and a core switch within the same AS (rather than using Option C with LDP).


Posted on 22 February 2022   10 min read

SD-WAN service-side MPLS VPN

using bgp mpls vpn for service-side cisco sd-wan connections

This post goes through how to configure MPLS VPN on the service-side of a Cisco SD-WAN edge device, so the south-side towards non-SD-WAN devices. What I am trying to achieve is to advertise the differing SD-WAN VPN (VRF, why Cisco have to call these VPNs beats me) prefixes to a core switch (using a ASR in the lab) directly connected to the SD-WAN router. This could be accomplished using per-VRF interfaces (or sub-interfaces) and BGP peerings, but a neater solution is to pass all the routing information over one the BGP MPLS VPNv4 peering.


Posted on 27 May 2021   6 min read

The Evolution of Labbing

how the worlds changed

A trip down memory lane on how things have changed in labbing from using prehistoric switches bought on eBay through emulators that took longer to configure than the labs to the present day solutions that can programmatically build a multi-vendor lab in minutes. Kids today don’t know they are born…..


Posted on 23 March 2021   14 min read

Automate Leaf and Spine Deployment - Part6

post validation

The 6th post in the ‘Automate Leaf and Spine Deployment’ series goes through the validation of the fabric once deployment has been completed. A desired state validation file is built from the contents of the variable files and compared against the devices actual state to determine whether the fabric and all the services that run on top of it comply.


Posted on 20 March 2021   25 min read

Automate Leaf and Spine Deployment - Part5

fabric services: tenant, interface, route

The 5th post in the ‘Automate Leaf and Spine Deployment’ series goes through the deployment of the services that run on top of the fabric. These services are grouped into 3 categories, tenant, interface and routing. Services are configured only on the leaf and border switches, the spines have no need for them as they just route the VXLAN encapsulated packets with no knowledge or care of what is within them.


Posted on 23 February 2021   9 min read

Automate Leaf and Spine Deployment - Part4

deploying the fabric with ansible

The 4th post in the ‘Automate Leaf and Spine Deployment’ series goes through the creation of the base and fabric config snippets and their deployment to devices. Loopbacks, NVE and intra-fabric interfaces are configured and both the underlay and overlay routing protocol peerings formed leaving the fabric in a state ready for services to be added.


Posted on 13 February 2021   15 min read

Automate Leaf and Spine Deployment - Part3

fabric variables and dynamic inventory

The 3rd post in the ‘Automate Leaf and Spine Deployment’ series goes the through the variables from which the core fabric declaration is made and how this transposes into a dynamic inventory. This uses only the base and fabric roles to create the fabric ready for the service sub-roles (tenant, interface and route) to be deployed on top of the fabric at a later stage.