routeprotocol
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Multicast Source Sparse Mode Registration
When the source for the group sends a packet, the first hop router attached to that source is required to register the source with the rendezvous point. The rendezvous point is also requested to build a tree back towards the first hop router. The first hop route encapsulates multicast data from the source into a…
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PIM Dense Mode
PIM dense mode constructs the multicast tree by flooding traffic out of every interface from the source to every dense mode router across the network. PIM dense mode is a suitable configuration where receivers of the multicast group are located across every subnet on the network. It is applicable to small networks, but not recommended…
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PIM Operating Modes
There are five operating PIM modes: PIM Dense Mode (PIM-DM) PIM Spare Mode (PIM-SM) PIM Spare Dense Mode PIM Source Specific Multicast (PIM-SSM) PIM Bidirectional Mode (Bidir-PIM) PIM Control messages are sent using IP Protocol 103. Register and register stop messages can be sent using unicast, or multicast with a time-to-live of 1 to all…
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PIM Terminlogy
Reverse Path Forwarding (RPF) Interface The reverse path forwarding interface is the interface with the lowest cost path to the IP address of the root of the shortest path tree (the source of the multicast stream). The lowest cost is based on the factors of administrative distance and metric. If there are multiple interfaces with…
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PIM Distribution Trees
A multicast router will create a distribution tree that will define the path multicast traffic follows to reach receiver devices. There are two types of multicast distribution trees known as source trees. They are also known as shortest path trees, SPTs and shared trees. Source Tree A source tree is a multicast distribution tree where…
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PIM – Protocol Independent Multicast
Hosts utilise IGMP to join a multicast group, this works perfectly fine when the router that the membership join request gets sent to also hosts the subnet that sends out the multicast traffic flows. If the receiving host and the multicast source router are several hops apart, routing between the routers will need to be…
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IGMP Snooping
IGMP snooping is a method that allows switches to only send traffic to interested receivers of multicast packet streams. IGMP snooping helps switches to optimise forwarding and minimise flooding of multicast streams to all connected ports on their device. Typically with unicast traffic, switches learn about MAC addresses and where they belong to by inspecting…
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Testing a NTP Server from Windows
You can test NTP from within a Windows command prompt using the utility w32tm w32tm /stripchart /computer:192.168.x.x /dataonly Example of a working NTP server query: w32tm /stripchart /computer:192.168.x.x /dataonly Tracking 192.168.x.x [192.168.x.x:123]. The current time is 12/08/2021 14:57:44. 14:57:44, +03.8630391s 14:57:46, +03.8583498s 14:57:48, +03.8599084s Example of a not working NTP server query: w32tm /stripchart /computer:192.168.x.x…
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IGMP Version 3
When a host in IGMPv2 sends a membership report to join a multicast group, it does not specify the source that it would like to receive the multicast traffic from. IGMPv3 is an extension on top of IGMPv2 that adds support for the multicast source filtering, giving the host a choice to pick the source…
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IGMP Version 2
IGMP Version 2 uses a message format 32 bits in size, with three fields. The first 8 bits are the type, the next 8 bits are the max response time, and the final 16 bits are a checksum. This message is encapsulated inside of an IP packet with a protocol number of 2. The message…