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CCNP

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Answer 50 questions in 15 minutes.
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Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. Which IOS command shows what version of IGMP is running?
BPG will find an exact match. BGP
Router#show ip igmp interface fa0/0 Multicast
Member of a group: Router#(config) ip igmp join-group group-address Statically connected: Router#(config) ip igmp join-group group-address In this mode router forwards (fast switches) group packets but itself does not accept group
Must insure loopback is reachable in the routing table. BGP

2. Explain the BGP route decision process? How many routes does it select? Where do they go? Where do the ones go that are not used?
BPG will find an exact match. BGP
EBGP will only peer to direclty connected neighbors and a loopback is considered one hop away. With eBGP peering to a loopback you must enable eBGP Multihop. R1(config-router)# neighbor 192.168.1.1 ebgp-multihop 2 BGP
BGP not designed for load balancing (by default). BGP selected the SINGLE best path to a destination and places it in the routing table; the rest are kept in the BGP Table. Paths are chosen based on policy. BGP eliminates paths until one p
WM List of AS numbers pre-pended with a list of AS numbers that the route has traversed and the originating AS at the end. 'Path to 192.168.1.0 is (65500 - 65420 - 65874)' This insures a loop-free environment. If BGP receives a

3. What is a BGP route reflector - What is it purpose?
The unicast routing table. No routing updates are sent between PIM routers. Multicast
Determines upstream and downstream interfaces. Uses the unicast routing table to insure that only one interface is considered to be and incoming interface for the source. RPF makes sure that if data is looped around is not forwarded. 
Sends a leave message to 224.0.0.2 Router then sends a group specific query Remaining member(s) send a report so group remains active. Multicast
Since IBGP learned routes are never propagate to other IBGP peer - full mesh of IBPG peers is required within an AS. THIS IS NOT SCALABLE. RR allow the propagation of routes learned by IBGP to other IBGP peers without having a full mesh of IBGP

4. What is a BGP peer group?

5. What is the IBGP Split Horizon rule? What does this accomplish?
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 Multicast
The BGP Table Command = show ip bgp BGP
* = Best route > = Route has been inserted into the routing table BGP
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP

6. What is the solution to establishing neighbor relationships when multiple paths exist? What are the command to establish this? What command to tell R1 to use its loopback0 interface as the update source neighbor 192.168.1.1.
R1(config-router)# neighbor 192.168.1.1 next-hop-self Cause each routers outgoing interface that the route traverse wihtin the AS (iBPG peers) to annouce itself as the 'next hop' instead of the next hop into the neighboring AS. 
Group of BGP routers being configured that have the same update policy. Similar to a 'template'; members then assigned to the peer group. BGP
Reverse Path Forwarding is the forwarding logic multicast of multicast. It is the opposite of unicast in that is forwards AWAY from source as opposed to towards the receiver. Multicast
Use loopback interface to establish the neighbor. (i.e. peer to a loopback interface) Tell BGP to use the lookback interface as teh source of updates R1(config-router)# neighbor 192.168.1.1 update-source loopback0 BGP

7. Explain the IGMPv3 membership process and new features.
* = Best route > = Route has been inserted into the routing table BGP
RFC - 3376 Ability to filter multicast source (can be picky) IGMPv3 membership report goes to 224.0.0.22 and may include the multicast hosts it will accept or deny. Multicast
Router#(config) router bgp 1 Router#(config-router) neighbor 192.168.1.1 remote-as 1 Router#(config-router) network 192.168.0. mask 255.255.255.0 BGP
OT Allows the router to 'tag' and thus implement policy based on this tag. BGP

8. What are the commands to enable multicast routing on a router?
Globally: Router(config)# ip multicast-routing Per Interface: Router(config-if)# ip pim dense-mode Enabling PIM on an interface also enables IGMP operation on that interface. Multicast
Using a Distribute List to filter outbound routing updates. BGP
It actually determines which networks are advertised. BGP
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword BGP

9. Explain the AS format and ranges?
16 bit number 1 to 65535 1-64511: Public AS 64512-6535: Reserved for private AS BGP
BGP specifies that it can advertise to its peers in neighboring AS's only routes that it uses. BGP cannot influence how a neighboring AS will route your traffic BUT it can influence how your traffic gets to the neighboring AS. BGP
Well know predefined group Directory - sd / SDP Webpage/URL Email link Multicast
Partial mesh iBPG is where not all BGP speaks within and AS have an established neighbor relationship. Full mesh is every BGP speaker has a neighbor (peer) with each other. Routing updates are not replcated in iBPG the peers do not pass i

10. Explain the Weight attribute.
O Cisco only. Routes with higher weight are preferred (0 - 65535) . Paths that the router originates have 32768; other paths have default of 0. BGP
BGP specifies that it can advertise to its peers in neighboring AS's only routes that it uses. BGP cannot influence how a neighboring AS will route your traffic BUT it can influence how your traffic gets to the neighboring AS. BGP
Since IBGP learned routes are never propagate to other IBGP peer - full mesh of IBPG peers is required within an AS. THIS IS NOT SCALABLE. RR allow the propagation of routes learned by IBGP to other IBGP peers without having a full mesh of IBGP
Default-Network Static route BGP

11. What is the command to enable BPG authentication?
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword BGP
R2(config)# access-list 1 permit 192.168.0.0 0.0.0.255 R1(config-router)# neighbor 10.1.1.1 distribute-list 1 out R1(config-router)# neighbor 10.1.1.2 distribute-list 1 out BGP
Source Tree - Source-based tree's are rooted at the source. Source tree created for each new group. Also called shortest path tree (SPT's). Shared Tree - Single tree that is shared between all sources; single common root called the rendezvous p

12. Explain what role IGMP plays.
O Cisco only. Routes with higher weight are preferred (0 - 65535) . Paths that the router originates have 32768; other paths have default of 0. BGP
Language between local router interface and hosts. IGMP - ICMP - similarities TTL is usually 1; RFC states it should never leave local subnet. Creates and maintains group membership for hosts wishing to participate in a multicast grou
AS-Path Next Hop Origin BGP
Determines upstream and downstream interfaces. Uses the unicast routing table to insure that only one interface is considered to be and incoming interface for the source. RPF makes sure that if data is looped around is not forwarded. 

13. When creating a BGP neighbor relationship to a loopback interface what must be remember in the context of routing?
Cluster - combination of RR and its clients. Can have multiple clusters in an AS. Originator ID - carries router ID of the route's originator Cluster ID - configured when multiple RR in a cluster. Cluster list - sequence of cluster ID
RFC - 3376 Ability to filter multicast source (can be picky) IGMPv3 membership report goes to 224.0.0.22 and may include the multicast hosts it will accept or deny. Multicast
IGMP Snooping - requires special ASICS can degrade performance with it; is supported by multiple vendors. CGMP - Cisco proprietary - only work on Cisco hardware; resource friendly GMRP - Replaced by MRP; obscure Manually - Performance
Must insure loopback is reachable in the routing table. BGP

14. Explain the relationship between MBone - DVMRP - PIM - IGMP - CGMP hosts - routers and switches?

15. What is the full mesh versus partial mesh IBGP and What are the implications of each?
The is the multicast bit. Multicast
Partial mesh iBPG is where not all BGP speaks within and AS have an established neighbor relationship. Full mesh is every BGP speaker has a neighbor (peer) with each other. Routing updates are not replcated in iBPG the peers do not pass i
BGP peer BGP
Globally: Router(config)# ip multicast-routing Per Interface: Router(config-if)# ip pim dense-mode Enabling PIM on an interface also enables IGMP operation on that interface. Multicast

16. What is the significance of the 8th bit in the MAC address?
OT Allows the router to 'tag' and thus implement policy based on this tag. BGP
It actually determines which networks are advertised. BGP
The is the multicast bit. Multicast
BGP peer BGP

17. What are the basic commands to enable BGP - define a BGP peer relationship and advertise a network?
Router#(config) router bgp 1 Router#(config-router) neighbor 192.168.1.1 remote-as 1 Router#(config-router) network 192.168.0. mask 255.255.255.0 BGP
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
WM List of AS numbers pre-pended with a list of AS numbers that the route has traversed and the originating AS at the end. 'Path to 192.168.1.0 is (65500 - 65420 - 65874)' This insures a loop-free environment. If BGP receives a
Dense mode interfaces are always added to the table. Sparse mode interfaces are added to the table only when periodic join messages are received from downstream routers - or when a directly connected member is on the interface Multi

18. Within the layer 3 multicast address space - name 3 reserved scopes and their purpose.
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast
Local scoped: 224.0.0.0 - 224.0.0.255 TTL of 1; Never to leave local network - for routing protocols and other network maintenance. Global scoped: 224.0.1.0 - 238.255.255.255 MBone dynamically allocate throughout Internet Limited/
WM Next hop address is entry point into the next AS along the path to that destination network. It does a recursive lookup to the routing table which should have learned the route from its IGP. in IBGP the next hop advertised by EBGP should
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword BGP

19. What is the key difference between how a multicast routing protocol forwards packets versus a unicast routing protocol?
Dense mode interfaces are always added to the table. Sparse mode interfaces are added to the table only when periodic join messages are received from downstream routers - or when a directly connected member is on the interface Multi
Unicast uses a routing table looking and forwards towards the destination address. Multicast forwards out multiple interfaces and away from the source and towards multiple destinations using a distribution tree. Multicast
The unicast routing table. No routing updates are sent between PIM routers. Multicast
Sends a leave message to 224.0.0.2 Router then sends a group specific query Remaining member(s) send a report so group remains active. Multicast

20. What are 2 stipulations of advertising networks BGP?

21. What are the methods to control multicast within the layer 2 domain? What are some benefits & drawbacks of each?
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP
R2(config)# access-list 1 permit 192.168.0.0 0.0.0.255 R1(config-router)# neighbor 10.1.1.1 distribute-list 1 out R1(config-router)# neighbor 10.1.1.2 distribute-list 1 out BGP
IGMP Snooping - requires special ASICS can degrade performance with it; is supported by multiple vendors. CGMP - Cisco proprietary - only work on Cisco hardware; resource friendly GMRP - Replaced by MRP; obscure Manually - Performance
Allow router to operate in sparse mode and dense mode at the same time. Supports multiple RP's and automatic RP selection for each multicast source. Support auto-RP - bootstrap router (BSR) or statically defined RP's with minimal configurat

22. What is the difference between iBGP and eBGP?
Links = n(n-1)/2 BGP
Show ip bgp - Shows entire BGP topology database (BGP table) show ip bgp rib-failure - Displays BGP routes not installd into the routing information base (RIB) and reason they were not installed. show ip bgp neighbors - Displays
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP

23. What config would be used to configured an outbound BGP distribute list to block all routes from being advertised except ones from 192.168.0.0 /24 network to neighbors 10.1.1.1 and 10.1.1.2?
Globally: Router(config)# ip multicast-routing Per Interface: Router(config-if)# ip pim dense-mode Enabling PIM on an interface also enables IGMP operation on that interface. Multicast
R2(config)# access-list 1 permit 192.168.0.0 0.0.0.255 R1(config-router)# neighbor 10.1.1.1 distribute-list 1 out R1(config-router)# neighbor 10.1.1.2 distribute-list 1 out BGP
Source Tree - Source-based tree's are rooted at the source. Source tree created for each new group. Also called shortest path tree (SPT's). Shared Tree - Single tree that is shared between all sources; single common root called the rendezvous p
Idle - Router looking in routing table to see if route exists to neighbor. [Active - When no response to Open message] Connect - Router found route to neighbor and has performed the TCP three-way handshake Open Sent

24. Name 4 verification commands for BGP and what they display?
Reverse Path Forwarding is the forwarding logic multicast of multicast. It is the opposite of unicast in that is forwards AWAY from source as opposed to towards the receiver. Multicast
The router will not accept a routing update that includes its AS number in the path. BGP
Language between local router interface and hosts. IGMP - ICMP - similarities TTL is usually 1; RFC states it should never leave local subnet. Creates and maintains group membership for hosts wishing to participate in a multicast grou
Show ip bgp - Shows entire BGP topology database (BGP table) show ip bgp rib-failure - Displays BGP routes not installd into the routing information base (RIB) and reason they were not installed. show ip bgp neighbors - Displays

25. What entities are responsible for allocating BGP AS numbers?
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP
BGP not designed for load balancing (by default). BGP selected the SINGLE best path to a destination and places it in the routing table; the rest are kept in the BGP Table. Paths are chosen based on policy. BGP eliminates paths until one p
BPG will find an exact match. BGP
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast

26. What is one mechanism that GURANTEES the BGP AS path is loop free?
BGP specifies that it can advertise to its peers in neighboring AS's only routes that it uses. BGP cannot influence how a neighboring AS will route your traffic BUT it can influence how your traffic gets to the neighboring AS. BGP
The router will not accept a routing update that includes its AS number in the path. BGP
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
Member of a group: Router#(config) ip igmp join-group group-address Statically connected: Router#(config) ip igmp join-group group-address In this mode router forwards (fast switches) group packets but itself does not accept group

27. Explain CGMP.

28. Explain the contents of the BGP update message.
When AS has more than one connection to the Internet it is called multihoming. Inbound reliability Better performance by selecting more optimal paths Multihoming can be to one ISP or to several. BGP
Globally: Router(config)# ip multicast-routing Per Interface: Router(config-if)# ip pim dense-mode Enabling PIM on an interface also enables IGMP operation on that interface. Multicast
Variable length sequence of path attributes Attribute Type -1 byte flag field - 1 byte type code Attribute Length Attribute Value Attribute flag field = 0000 0000 W | O - T | N - P | C BGP
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP

29. State how IGMPv1 operates.
RFC 2236 Leave and join latency resolved Group specific query to G instead of 224.0.0.1 Leave group message Election of querier (lowest IP) on broadcast medium with multiple routers Multicast
Idle - Router looking in routing table to see if route exists to neighbor. [Active - When no response to Open message] Connect - Router found route to neighbor and has performed the TCP three-way handshake Open Sent
RFC 1112 Sends membership query every 60 - 120 seconds to 224.0.0.1 Hosts send membership report in response to the query Multicast
This router originated the route. BGP

30. Explain the Community attribute.

31. What command will produce the following output and What is it displaying? <img src='5d3c9233dd205ee4319ef0ac2fc07460.jpg' />
224.0.0.1 - All systems 224.0.0.2 - All routers 224.0.0.4 - DVMRP routers 224.0.0.5 - All OSPF 224.0.0.6 - All OSPF DR 224.0.0.9 - RIP v2 routers 224.0.0.10 - EIGRP routers 224.0.0.13 - PIM routers 224.0.0.15 -
Cluster - combination of RR and its clients. Can have multiple clusters in an AS. Originator ID - carries router ID of the route's originator Cluster ID - configured when multiple RR in a cluster. Cluster list - sequence of cluster ID
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. Multicast
The BGP Table Command = show ip bgp BGP

32. State 3 functions SDR performs?
RFC 2236 Leave and join latency resolved Group specific query to G instead of 224.0.0.1 Leave group message Election of querier (lowest IP) on broadcast medium with multiple routers Multicast
Router#show ip igmp group Group address - interface - uptime - expires - and last reporter. Multicast
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast

33. Describe how PIM-Sparse-Dense operates.

34. Explain the concept of RPF.
WM One of three values: IGP - Route is interior to the originating AS. (BGP table shows 'i') EGP - Route learned via EGP. (BGP table shows 'e') Incomplete - Routes origin is unknown - usually when redistributed. (BGP table shows
Reverse Path Forwarding is the forwarding logic multicast of multicast. It is the opposite of unicast in that is forwards AWAY from source as opposed to towards the receiver. Multicast
Concatenation of the first (high order) 25 bits of the reserved MAC address range with the last (low order)23 bits of the multicast group IP address. 5 bits of overlap allowing for 32 address (2^5) for each multicast MAC address. 25 bits + 23 bits R1(config-router)#neighbor 10.1.1.1 remote-as 64513 R1(config-router)#neighbor 10.1.1.1 peer-group MyPeers BGP

35. What is the command to configure a BGP RR?
Path Vector - policy based routing protocol. Uses BGP attributes are the 'metric'. Path it decides it based on 'hops' where hop is Autonomous Systems. BGP
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP
Rule: Router must be known by an IGP before it may be advertised by BGP peers. Prevents 'blackholes' when AS is a transit network and not all speaker are running BGP Should be left on it AS is a transit AS and not all routers run BGP. 
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP

36. What are three different common ways to perform BGP multihoming with regard to routing table?
Determines upstream and downstream interfaces. Uses the unicast routing table to insure that only one interface is considered to be and incoming interface for the source. RPF makes sure that if data is looped around is not forwarded. 
One-to-many: video distribution Many-to-many: Collaboration Many-to-one: auction - polling or data collection Few-to-many: auction - polling or data collection Multicast
Path Vector - policy based routing protocol. Uses BGP attributes are the 'metric'. Path it decides it based on 'hops' where hop is Autonomous Systems. BGP
ISP passes only default route to AS. ISP passes default route and provider owned select routes to AS. ISP passes all routes to AS. BGP

37. What are the administrative distances of eBGP and iBGP?
Use loopback interface to establish the neighbor. (i.e. peer to a loopback interface) Tell BGP to use the lookback interface as teh source of updates R1(config-router)# neighbor 192.168.1.1 update-source loopback0 BGP
WM Next hop address is entry point into the next AS along the path to that destination network. It does a recursive lookup to the routing table which should have learned the route from its IGP. in IBGP the next hop advertised by EBGP should
IGMP is a layer 3 protocol Switches treat multicast just like broadcast (forward out all ports except the one one which is was received) By definition a pure layer 2 devices do not have a mechanism to see IGMP packets or facilitate the rela
EBGP = 20 iBGP = 200 BGP

38. What are some of the obstacles with IGMP and multicast in general as it relates to layer 2/switches?
1. Weight - Administrative preference (Highest) 2. Local Preference - Communicated between peers within AS (Highest) 3. Self-originated - Prefer path originated locally (True) 4. AS Path - Minimize AS hops (Shortest)<
WM Next hop address is entry point into the next AS along the path to that destination network. It does a recursive lookup to the routing table which should have learned the route from its IGP. in IBGP the next hop advertised by EBGP should
224.0.0.1 - All systems 224.0.0.2 - All routers 224.0.0.4 - DVMRP routers 224.0.0.5 - All OSPF 224.0.0.6 - All OSPF DR 224.0.0.9 - RIP v2 routers 224.0.0.10 - EIGRP routers 224.0.0.13 - PIM routers 224.0.0.15 -
IGMP is a layer 3 protocol Switches treat multicast just like broadcast (forward out all ports except the one one which is was received) By definition a pure layer 2 devices do not have a mechanism to see IGMP packets or facilitate the rela

39. Describe 4 multicast application models and give an example of each?
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 Multicast
Update from client peer - sends update to all non-client peers and client peers except for originating peer. Update from non-client peer - send update to all clients in the cluster. Update from EBGP peer - update sent to all client peers an
One-to-many: video distribution Many-to-many: Collaboration Many-to-one: auction - polling or data collection Few-to-many: auction - polling or data collection Multicast
Unicast uses a routing table looking and forwards towards the destination address. Multicast forwards out multiple interfaces and away from the source and towards multiple destinations using a distribution tree. Multicast

40. What effect does (S -G) and (* -G) entries have on router CPU?
SPT (S -G) consume more memory because there is an entry for each source BUT traffic is sent over optimal path to receiver. Shared distribution tree state entries (* -G) consume less CPU but may take suboptimal path to receiver. Multicast
16 bit number 1 to 65535 1-64511: Public AS 64512-6535: Reserved for private AS BGP
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
Source Tree - Source-based tree's are rooted at the source. Source tree created for each new group. Also called shortest path tree (SPT's). Shared Tree - Single tree that is shared between all sources; single common root called the rendezvous p

41. What is the formula to determine number of links in a full mesh topology?
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
This should only be for ISP's An improperly configured AS (that is not meant to be a transit) could inadvertently become one. BGP
Most applications rely on UDP Security issues Out of order delivery & duplicate packets are a possibility during topology changes. Lack of windowing/congestion control. Multicast
Links = n(n-1)/2 BGP

42. What advantage does multicast offer?
Efficiency Performance Scalability with applications Multicast
BGP not designed for load balancing (by default). BGP selected the SINGLE best path to a destination and places it in the routing table; the rest are kept in the BGP Table. Paths are chosen based on policy. BGP eliminates paths until one p
Since IBGP learned routes are never propagate to other IBGP peer - full mesh of IBPG peers is required within an AS. THIS IS NOT SCALABLE. RR allow the propagation of routes learned by IBGP to other IBGP peers without having a full mesh of IBGP
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP

43. How is the BGP network command differ from IGP's?
Reverse Path Forwarding is the forwarding logic multicast of multicast. It is the opposite of unicast in that is forwards AWAY from source as opposed to towards the receiver. Multicast
The BGP Table Command = show ip bgp BGP
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP
It actually determines which networks are advertised. BGP

44. Explain the Next-Hop attribute. How does this differ from IGP's? In what environment might this be problematic?
BGP peer BGP
Efficiency Performance Scalability with applications Multicast
WM Next hop address is entry point into the next AS along the path to that destination network. It does a recursive lookup to the routing table which should have learned the route from its IGP. in IBGP the next hop advertised by EBGP should
BPG will find an exact match. BGP

45. Describe how and IGMPv2 host leaves. What is the interaction between host and router look like?
WD Dictates which path is preferred to exit the AS. Higher is is preferred - default is 100 on Cisco. Obviously for this to be relevant there must be multiple exit points for the route. 'Influences outbound traffic for an AS' Atomic Aggregate BGP
Use loopback interface to establish the neighbor. (i.e. peer to a loopback interface) Tell BGP to use the lookback interface as teh source of updates R1(config-router)# neighbor 192.168.1.1 update-source loopback0 BGP
Sends a leave message to 224.0.0.2 Router then sends a group specific query Remaining member(s) send a report so group remains active. Multicast

46. Explain the Origin attribute.

47. What are the 3 BGP tables and What is in them?
BGP Table - BGP topology database - information BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. BGP
Loopback more resilient than physical interfaces. BGP
Rule: Router must be known by an IGP before it may be advertised by BGP peers. Prevents 'blackholes' when AS is a transit network and not all speaker are running BGP Should be left on it AS is a transit AS and not all routers run BGP. 
RFC 2362 Pull model - traffic only forwarded to the parts of the network that need it. Sender registers with the RP which is a proxy to group members. Last hop routers to receiver knows the group RP IP address and sends a (* -G) join toward

48. What command is used to override the Next-Hop attribute of BGP? What does this do and when would you use this?

49. How does a host learn about available multicast streams?
Path Vector - policy based routing protocol. Uses BGP attributes are the 'metric'. Path it decides it based on 'hops' where hop is Autonomous Systems. BGP
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
The router will not accept a routing update that includes its AS number in the path. BGP
Well know predefined group Directory - sd / SDP Webpage/URL Email link Multicast

50. What block of multicast MAC addresses belong to multicast?
The unicast routing table. No routing updates are sent between PIM routers. Multicast
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. Multicast
Concatenation of the first (high order) 25 bits of the reserved MAC address range with the last (low order)23 bits of the multicast group IP address. 5 bits of overlap allowing for 32 address (2^5) for each multicast MAC address. 25 bits + 23 bits (* -G) - 'Star comma G'; Any source sending to the group. Traffic forwar