PFC (Priority Flow Control)

PFC (Priority Flow Control) (IEEE 802.1Qbb) provides backward congestion notification on Layer 2 Ethernet by sending PAUSE frame selectively based on 802.1p COS value. Initially, IEEE 802.3x PAUSE works by sending PAUSE frame for any traffic flow regardless.

lacp suspend-individual

When an end-host configured with port-channel LACP or NIC- or link-teaming, it requires the adjacent switch ports to receive LACP PDU to be able to start the negotiation and bring the port-channel to Up and Operational status. Without the end-host sending these LACP PDU, the switch ports will keep its status as down. It sounds…

Cisco Catalyst 9000 (C9K)

Cisco Catalyst 9000 (C9K). Highlights 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…

RIPv2 Notes

RFC 2453 – RIP Version 2 Distance Vector IGP. Routers only know what directly connected neighbours tell them (Routing by Rumour). Routers only know what is the routing as it told by neighbours but does not actually know the state/condition of the route itself.

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…

MST Notes

History 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…

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…

PIM Sparse-Mode (SM) Notes – RFC 4601

Uses both Shared-Tree (*,G) and Source-Tree (S,G). PIM Sparse-Mode (SM) steps: 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….

Multicast: Overview

The way an IP packet delivered from server to client or vice versa is mostly known as unicast delivery. A server will need to know the client’s IP Address and assign this client’s IP address to the IP packet to be delivered. The more clients the server has, the more packets should be created and…