24 Aug

IGMP Snooping on single switch

The IGMP Snooping is a nice feature to limit propagation of multicast traffic in Layer 2 Ethernet network. It listens to IGMP (Internet Group Management Protocol) messages traversing the network to learn about source and receivers. Using this information switch builds a map of links where it replicates the multicast frames. What if we do not have this feature enabled? The switch will treat multicast frames as an unknown type and will broadcast over all active ports no matter is there is receiver interested in frames from the particular multicast group or not.

IGMP Snooping on a single switch is useful to limit propagation of multicast frames when source and receivers are in same layer 2 broadcast domain, in the same VLAN. IGMP Snooping is enabled on Cisco switches by default, but it does not mean it will work out-of-box.

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18 Aug

Generate multicast​ traffic in VIRL using Ostinato

Cisco and VIRL logos

Ostinato is a traffic generator. You can use it to craft packets and send flow into your network. You can even send multiple streams if required. It is a tool that network admins and developers should use for testing the system or application against various scenarios. Ostinato is by default available on Cisco VIRL so we can use it as a packet generator in our simulations.

Ostinato consists of two components – the LXC image run in a simulation that generates the traffic and GUI frontend. In this article, I will show you how to use it to generate a multicast stream in VIRL simulation.

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