Category Archives: Cisco

Cisco Catalyst 9000 (C9K)

Cisco Catalyst 9000 (C9K).


  • Same binary image across all C9K; Open IOS-XE 16.5. Note. the term Open IOS-XE is for the new released IOS-XE starting on version 16.
    • Using database approach to store configuration.
    • SMU (Software Maintenance Update). To get rid of bug, there is patch which can be installed without upgrading the IOS-XE and subsequently no outage.
    • Support Data Models (Netconf/Yang); Google OpenConfig.
  • Programmable ASIC via FlexParser.
  • Micro Engines to off-load CPU processing requirement.
  • Three models:
    • Cisco Catalyst 9300. Fixed Access.
    • Cisco Catalyst 9400. Modular Access.
    • Cisco Catalyst 9500. Fixed Core.
      Continue reading

INEv5 – VIRL Topology – Lan Switching Spanning Tree Initial

I have been using INE (Internetwork Expert) CCIE RS rack rental but sometimes I find it a bit too slow for telnet response. So, with the advent of Cisco VIRL I have created the similar lab topology so I can lab the workbooks with fast response.

Initial configuration is saved in the .virl file but it is also available in a separate file just in case VIRL does not load the full config (in this case VLANs).

Topology diagram is also available with the conversion from INE lab to VIRL lab.
Continue reading

Visio Flat Network Icon

I have created just a few standard Microsoft Visio Flat Network icons and they are available for all to use and share. The idea was to have network icons that are 2D instead of the 3D version for drawing consistency and making it easier to apply Visio diagram theme.

These icons allow you to un-group and make changes to suit your need. The connectors are also created around the icon to allow attaching a line.

I created these icons on Visio 2013 but I’m not sure the compatibility with the earlier version so I’ve made these available in Visio 2013 (.vssx) and earlier Visio format (.vss).
Continue reading

MST Notes


Spanning Tree Protocol (STP) is a protocol to ensure there is no loop in layer 2 network. This protocol was invented by Radia Perlman in 1985 and published as a standard originally as IEEE 802.1D-1990.

In essence, STP works by sending a probe to every layer 2 switches and decides which link should be block if there is a loop.

Initially STP was used with one instance. This is when there was no understanding of VLAN which was introduced later in IEEE 802.1Q. Mono Spanning Tree runs a single Spanning Tree for all VLANs. Since it uses one Spanning Tree instance for all VLANs, it lacks the ability to engineer one path over another. All VLANs will have to share the same path and fate.
Continue reading

IGMPv2 – RFC 2236

While PIM controls the communication between multicast routers, IGMP is the control protocol between routers and hosts. IGMP is similar with ICMP and it has IP protocol number 2. Because the intention is the communcation between hosts and routers, it is only sent as a link-local packet that has TTL of 1 in the IP packet header.

Continue reading

PIM Sparse-Mode (SM) Notes – RFC 4601

Uses both Shared-Tree (*,G) and Source-Tree (S,G).

PIM Sparse-Mode (SM) steps:

  1. Discover PIM neighbor and elect DR.
    PIM is the infrastructure to deliver the multicast packet. It builds the multicast network hop-by-hop. It takes the advantage of the routing table to perform RPF but it does not really matter what routing protocol derives it from. Hence this is why it is called Protocol Independent Multicast (PIM).
  2. Continue reading