CCNP ENCOR v8 Chapters 13 – 14: Multicast and QoS Test Online

Hint

The internet Assigned Numbers authority has assigned two group addresses, 224.0.0.39 and 224.0.1.40, for Auto-RP configuration in order to announce the RP in the multicast group.

Hint

PIM sparse mode chooses one or more routers to operate as rendezvous points (RPs). An RP is a single common root placed at a chosen point of a shared distribution tree.

Hint

BSR (bootstrap router) messages are forwarded out of every PIM-enabled interface and use the all PIM router address 224.0.0.13 with a TTL of 1.

Hint

The multicast routing information base (MRIB) is a topology table that is also known as the multicast route table (mroute). The MRIB is built using PIM and the routing table. It contains the source S, group G, incoming interfaces (IIF), outgoing interfaces (OIFs), and RPF neighbor information for each multicast route as well as other multicast-related information. The command show ip mroute is used to display the full contents of the IP multicast routing table.

Hint

When a receiver wants to receive multicast feed from a particular multicast service, it will send a IGMP join message with the multicast IP address of the service and then reprogram the receiver interface with the matching multicast MAC address. To find the matching MAC address, do the following: Convert the IP multicast address 239.255.8.5 to binary form, 11101111.11111111.00001000.00000101 Separate the 23 low-order binary bits from the converted address, 1111111.00001000.00000101 Convert these bits to hexadecimal: 7F:08:05 Because the first 24bits of a multicast MAC address are 01.00.5E, The resulting multicast MAC address is then 01:00:5E:7F:08:05.

Hint

In a shared tree uses a rendezvous point (RP) as the tree root instead of the multicast source. Multicast traffic is forwarded down the shared tree to the group address (G). For this reason the forwarding state is referred to as (*,G).

Hint

IGMPv3 is an extension of IGMPv2 with added support for multicast source filtering done through the use of a new message type called Version 3 membership report. It supports applications that explicitly signal sources that want to receive multicast traffic by using the membership report in the Include or Exclude mode.

Hint

RP mapping agents advertise the RP mappings to the well-known multicast group address, 224.0.1.40 (Cisco-RP-Discovery). Advertisements are sent every 60 seconds by default, or when changes are detected. All PIM-enabled routers join 224.0.1.40 and store the RP mappings in cache.

Hint

IGMP snooping stops multicast traffic from being broadcast on the access layer switches by examining IGMP joins that are sent by receivers and maintaining a table of interfaces to IGMP joins.

Hint

The two IGMP modes that are used to signal membership are Include mode (the receiver announces membership to a multicast group and provides a include list) and Exclude mode (receiver announces membership to multicast group and provides exclude list).

Hint

PIM dense mode is used in a multicast group that is densely populated across the network. PIM dense mode (PIM-DM) prunes expire after three minutes. This means that the flood and prune behavior of PIM dense mode repeats every three minutes and should be taken into account when designing a network for PIM-DM. A rendezvous point (RP) is required only in networks running Protocol Independent Multicast sparse mode (PIM-SM).

Hint

A C-RP advertises its willingness to be an RP every 60 seconds via RP announcement messages to the reserved well-known multicast group 224.0.1.39 (Cisco-RP-Announce). RP mapping agents join group 224.0.1.39 to receive the RP announcements.

Hint

PIM is a multicast routing protocol that routes multicast traffic between network segments by creating distribution trees. It makes packet-forwarding decisions independent of the unicast IP routing protocol that is running in the network. There are five operating PIM modes: PIM dense mode (PIM-DM) PIM sparse mode (PIM-SM) PIM sparse dense Mode PIM source specific multicast (PIM-SSM) PIM bidirectional mode (Bidir-PIM)

Hint

IGMPv3 is used to provide source filtering for Source Specific Multicast (SSM). IGMP snooping can be used to mitigate multicast flooding and optimize the forwarding of multicast traffic to interested receivers.

Hint

The bootstrap router (BSR) mechanism is used by PIM to discover and announce RP set information for each group prefix for all the routers in a PIM domain. This mechanism provides a fault-tolerant, automated RP discovery and distribution mechanism.

Hint

When the IntServ QoS model is being used, if network devices along a data path can reserve the required bandwidth, the originating application can begin transmitting. If the requested resource reservation cannot be allocated along the path, the originating application does not send any data.

Hint

IPv4 uses an 8-bit Type of Service field to mark packets at Layer 3 and IPv6 uses an 8-bit Traffic Class field to mark packets at Layer 3. The fields are used by receiving devices to forward the packets based on the appropriate assigned QoS policy.

Hint

Trusted endpoints are devices that have the capability to mark application traffic at Layer 2 or Layer 3. Trusted endpoints include the following: IP phones Wireless access points Videoconferencing gateways and systems IP conferencing stations and more

Hint

Best effort is the default packet forwarding design and provides no QoS. The differentiated services model enforces and applies QoS mechanisms on a hop-by-hop basis, not source to destination. Class-based weighted fair queuing and low latency queuing are queuing algorithms.

Hint

The Tc value is calculated by using the formula Bc (bits)/ CIR (bps) X 1000 TC = (15 Mb/150 Mbps) X 1000 Tc = (15,000,000 bits/150,000,000 pbs) X 1000 Tc = 100 ms

Hint

The Class of Service is a 3-bit, Layer 2 field that is used as part of quality of service (QOS) between switches. The CoS is also one of the values used for classification and marking of traffic.

Hint

The differentiated services code point (DSCP) protocol is used to mark a 6-bit field within the DiffServ field that allows for classification of up to 64 values used for QoS.

Hint

Because voice traffic is very sensitive to delay and jitter, to avoid packet drops care must taken to be ensure a maximum one-way latency of not more then 150ms.

Hint

Because voice traffic is very sensitive to latency and jitter, it would be better to keep it on a separate vlan and prioritize the traffic using QoS mechanisms. Such actions will ensure that the voice traffic has a dedicated bandwidth that is sufficient to meet its needs and the traffic is marked as priority over any other traffic.

Hint

The Single-Rate Two-Color Markers use a single token algorithm while the Single-Rate Three-Color markers use the two token bucket algorithm.

Hint

The traffic types and their associated DSCP values in a WLAN are as follows: Voice-EF Video-AF41 Best Effort-O Background-AF11

Hint

NBAR2 is a deep packet inspection engine that uses Layer 3 through 7 data to identify a variety of protocols. it can operate in either Protocol discovery mode or Modular QoS CLI (MQC) mode.