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CCNP

Instructions:

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. State how IGMPv1 operates.
RFC 1112 Sends membership query every 60 - 120 seconds to 224.0.0.1 Hosts send membership report in response to the query Multicast
When using the classful method - at least one subnet of the classful range must reside in the IP routing table. When using the classless method the exact subne
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
16 bit number 1 to 65535 1-64511: Public AS 64512-6535: Reserved for private AS BGP

2. Describe how PIM-DM operates.

3. Describe how and IGMPv2 host leaves. What is the interaction between host and router look like?
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
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
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 ISP passes default route and provider owned select routes to AS. ISP passes all routes to AS. BGP
When not all routers within a transit AS have consistent routing information - due to not running BGP or misconfiguration or BPG speakers. Routing information is advertised but since not all routers within AS can reach the destination traffic is halt
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. 

5. Explain the contents of the BGP update message.
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
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast
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
When not all routers within a transit AS have consistent routing information - due to not running BGP or misconfiguration or BPG speakers. Routing information is advertised but since not all routers within AS can reach the destination traffic is halt

6. What are the 3 BGP tables and What is in them?
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
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
BGP Table - BGP topology database - information BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. BGP
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

7. What is the key difference between how a multicast routing protocol forwards packets versus a unicast routing protocol?
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP
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
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'<br /
This router originated the route. BGP

8. What are the methods to control multicast within the layer 2 domain? What are some benefits & drawbacks of each?
Contains information on ONE path only Withdrawn routes - List of IP prefixes for routes being withdrawn. Path attributes - AS-Path - etc. Network layer reachability information - List of IP prefixes reachable by this path. 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
Works if router has multiple parallel paths to a destination. ONLY affect number of routes in IP routing table not the route selected at best in the BGP table. Will load balance across equal cost paths in EGP session. BGP
'Periodic Flood and Prune.' Initially floods multicast traffic (received on its RPF) to all its PIM neighbors. Traffic that arrives back at the router via a non-RPF is discarded. Prune messages are sent on all non-RPF interfaces and RPF int

9. Name the Well-known discretionary attributes.
The is the multicast bit. Multicast
EBGP = 20 iBGP = 200 BGP
Local preference Atomic Aggregate 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

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

11. What is a BGP route reflector - What is it purpose?
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
Using a Distribute List to filter outbound routing updates. 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
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

12. When creating a BGP neighbor relationship to a loopback interface what must be remember in the context of routing?
Must insure loopback is reachable in the routing table. BGP
This will advertise the entire classful network: R1(config-router)# network 10.1.1.0 This will advertise the the classless network: R1(config-router)# network 10.1.1.0 mask 255.255.255.0 BGP
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)<
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

13. Explain the Local Preference attribute. 

14. What is the IOS command to check for IGMP group members? What info does it reveal?
BGP peer BGP
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
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP
Router#show ip igmp group Group address - interface - uptime - expires - and last reporter. Multicast

15. What does a 0.0.0.0 signify in the Next Hop column in the BGP Table?
This router originated the route. BGP
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 -
The router will not accept a routing update that includes its AS number in the path. BGP
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast

16. What entities are responsible for allocating BGP AS numbers?
* = Best route > = Route has been inserted into the routing table 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
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP
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

17. What does PIM use for its multicast routing calculations?
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
This router originated the route. 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
The unicast routing table. No routing updates are sent between PIM routers. Multicast

18. IOS command to configure a rendezvous point .
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast
Using a Distribute List to filter outbound routing updates. BGP
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast
R1# clear ip bgp R1# clear ip bgp soft in R1# clear ip bgp * soft out R1# clear ip bgp 10.1.1.1 soft in BGP

19. What are the 6 BGP Neighbor states?
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' [Active - When no response to Open message] Connect - Router found route to neighbor and has performed the TCP three-way handshake Open Sent
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP
This router originated the route. BGP

20. 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?
'Periodic Flood and Prune.' Initially floods multicast traffic (received on its RPF) to all its PIM neighbors. Traffic that arrives back at the router via a non-RPF is discarded. Prune messages are sent on all non-RPF interfaces and RPF int
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
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
The is the multicast bit. Multicast

21. What is the IBGP Split Horizon rule? What does this accomplish?
The unicast routing table. No routing updates are sent between PIM routers. Multicast
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC 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
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP

22. What is the hop-by-hop routing paradigm of BGP?

23. What does IGMPv2 add?
BGP Table - BGP topology database - information BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. BGP
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. 
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/
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

24. What is a BGP peer group?

25. Name the Well-known mandatory attributes.
AS-Path Next Hop Origin BGP
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. Multicast
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP
Efficiency Performance Scalability with applications Multicast

26. What does a '*' and '>' mean in the BGP table?
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/
* = Best route > = Route has been inserted into the routing table BGP
It actually determines which networks are advertised. BGP
Open - Version - AS - Hold Time - BGP Router ID - Optional Parameters Keepalive - Sent every 60 seconds by default; hold time 180 Seconds. Update - Information on only ONE path; Notification - When error condition detected BGP

27. Within the layer 3 multicast address space - name 3 reserved scopes and their purpose.
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
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/
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword BGP
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

28. Explain the Next-Hop attribute. How does this differ from IGP's? In what environment might this be problematic?
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
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
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

29. What special consideration is there when peering to a eBGP neighbor using a loopback? What is the solution to this?
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
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
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
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. Multicast

30. What are the commands to enable multicast routing on a router?
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
This should only be for ISP's An improperly configured AS (that is not meant to be a transit) could inadvertently become one. 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
BGP Table - BGP topology database - information BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. BGP

31. 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.
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
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
The is the multicast bit. Multicast
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP

32. Explain the AS-Path attribute.

33. What are the basic commands to enable BGP - define a BGP peer relationship and advertise a network?
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
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast
Efficiency Performance Scalability with applications 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

34. What are two methods of establishing a gateway of last resort?
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/
Default-Network Static route BGP
When not all routers within a transit AS have consistent routing information - due to not running BGP or misconfiguration or BPG speakers. Routing information is advertised but since not all routers within AS can reach the destination traffic is halt
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast

35. What effect will placing a route to null0 have on BGP?
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP
Places it in the routing table. BGP
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP
BPG will find an exact match. BGP

36. What are some disadvantages of multicast?
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP
Loopback more resilient than physical interfaces. BGP
Links = n(n-1)/2 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

37. Which IOS command shows what version of IGMP is running?
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client 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
Router#show ip igmp interface fa0/0 Multicast
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast

38. Explain the Origin attribute.

39. Describe 4 multicast application models and give an example of each?
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
The is the multicast bit. 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
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. Name to enhancements to PIM.
When using the classful method - at least one subnet of the classful range must reside in the IP routing table. When using the classless method the exact subne
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast
Cisco Proprietary - between router and switch 'Client/Server': Router = CGMP Server - Switch = CGMP Client When router sees IGMP control message it creates a CGMP packet with the mutlicast MAC + client MAC; sends this to 'All CGMP Devices M

41. What advantage is there it establishing a neighbor relationship using a loopback interface?
Using a Distribute List to filter outbound routing updates. BGP
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
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword BGP
Loopback more resilient than physical interfaces. BGP

42. Name several common local scoped multicast addresses and their purpose.
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
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 -
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
Using a Distribute List to filter outbound routing updates. BGP

43. What is BGP multihoming and why would you want to do it?
Efficiency Performance Scalability with applications Multicast
When not all routers within a transit AS have consistent routing information - due to not running BGP or misconfiguration or BPG speakers. Routing information is advertised but since not all routers within AS can reach the destination traffic is halt
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
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. 

44. IOS command to dictate when a leaf router (in PIM-SM) will switch from shared to source tree.
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
The BGP Table Command = show ip bgp 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
Contains information on ONE path only Withdrawn routes - List of IP prefixes for routes being withdrawn. Path attributes - AS-Path - etc. Network layer reachability information - List of IP prefixes reachable by this path. BGP

45. Explain the Community attribute.

46. What is the command to configure a BGP RR? 
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client 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
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
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

47. Describe how PIM-Sparse-Dense operates.

48. What are the 4 BGP packet types? What do they contain?
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 -
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
Loopback more resilient than physical interfaces. BGP
Open - Version - AS - Hold Time - BGP Router ID - Optional Parameters Keepalive - Sent every 60 seconds by default; hold time 180 Seconds. Update - Information on only ONE path; Notification - When error condition detected BGP

49. What effect does (S -G) and (* -G) entries have on router CPU?
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)<
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
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
The router will not accept a routing update that includes its AS number in the path. BGP

50. What are the commands to configure a BGP peer group?
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
R1(config-router)#neighbor MyPeers peer-group R1(config-router)#neighbor 10.1.1.1 remote-as 64513 R1(config-router)#neighbor 10.1.1.1 peer-group MyPeers BGP
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast
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