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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. Describe how PIM-SM operates.
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
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
RFC 1112 Sends membership query every 60 - 120 seconds to 224.0.0.1 Hosts send membership report in response to the query 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 Allows the router to 'tag' and thus implement policy based on this tag. BGP
BGP peer 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. 
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

3. What effect does (S -G) and (* -G) entries have on router CPU?
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 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
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 BGP Table Command = show ip bgp BGP

4. What are the 3 BGP tables and What is in them?
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. 
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
BGP Table - BGP topology database - information BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. BGP
The router will not accept a routing update that includes its AS number in the path. BGP

5. What are the methods to control multicast within the layer 2 domain? What are some benefits & drawbacks of each?
<img src='9618cf01b9422f541fc213b74a3bd9de.png' /> Multicast
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
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
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

6. What are 2 stipulations of advertising networks BGP?

7. Name 4 verification commands for BGP and what they display?
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
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/
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
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. 

8. What advantage does multicast offer?
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword BGP
Efficiency Performance Scalability with applications Multicast
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
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP

9. What does a 0.0.0.0 signify in the Next Hop column in the BGP Table?
EBGP = 20 iBGP = 200 BGP
This router originated the route. 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
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

10. What is the signifigance of the neighbor address when establishing BGP neighbor in the context of network that has multiple paths to the neighbor?
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
Using a Distribute List to filter outbound routing updates. BGP
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
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP

11. Name 6 multicast routing protocols.
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
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode 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
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 

13. 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 should only be for ISP's An improperly configured AS (that is not meant to be a transit) could inadvertently become one. BGP
AS-Path Next Hop Origin BGP
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP

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

15. 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?
Must insure loopback is reachable in the routing table. BGP
This router originated the route. 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
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

16. State 3 functions SDR performs?
Efficiency Performance Scalability with applications Multicast
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. 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
Router#show ip igmp interface fa0/0 Multicast

17. 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?
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
Must insure loopback is reachable in the routing table. BGP
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
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

18. What is the multicast IP address space?
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
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 Multicast
Local preference Atomic Aggregate BGP
* = Best route > = Route has been inserted into the routing table BGP

19. How does a host learn about available multicast streams?
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
Well know predefined group Directory - sd / SDP Webpage/URL Email link Multicast
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP

20. Describe how PIM-Sparse-Dense operates.

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

22. What is the BGP Synchronization requirement and What does is prevent? When should it be left disabled? When should it be enabled?

23. Explain the AS format and ranges?
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
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. Multicast
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)<
16 bit number 1 to 65535 1-64511: Public AS 64512-6535: Reserved for private AS BGP

24. Name to enhancements to PIM.
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
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
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. Multicast

25. What are the commands to configure a BGP peer group?
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
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
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
Using a Distribute List to filter outbound routing updates. BGP

26. 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
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
The is the multicast bit. Multicast
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast

27. What is a BGP peer group?

28. IOS command to configure a rendezvous point .
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
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast
The router will not accept a routing update that includes its AS number in the path. BGP
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

29. After the path selection process - What does BGP do with the route?
Places it in the routing table. BGP
Well know predefined group Directory - sd / SDP Webpage/URL Email link Multicast
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)<
The is the multicast bit. Multicast

30. Describe how and IGMPv2 host leaves. What is the interaction between host and router look like?
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
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode 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
ON Displayed as metric in Cisco IOS; lower is preferred. Default is 0. Indicated to external AS the preferred path into the AS. 'Influence inbound traffic to an AS' By default ONLY compares if neighbors AS is same for all routes being

31. How does Source and Shared Distribution Tree models related to PIM-DM and PIM-SM?

32. What does a '*' and '>' mean in the BGP table?
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword 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
* = Best route > = Route has been inserted into the routing table BGP
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

33. What does IGMPv2 add?
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
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
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
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

34. Name a significant inefficiency with IGMPv1.
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
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)<
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
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast

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

36. Name what an update message may include.
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
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
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
Group of BGP routers being configured that have the same update policy. Similar to a 'template'; members then assigned to the peer group. BGP

37. What advantage is there it establishing a neighbor relationship using a loopback interface?
Loopback more resilient than physical interfaces. BGP
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 Multicast
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client 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

38. What are the commands to enable multicast routing on a router?
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 = 20 iBGP = 200 BGP
Must insure loopback is reachable in the routing table. 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

39. Name the Well-known mandatory attributes.
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
AS-Path Next Hop Origin BGP
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
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/

40. 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
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast
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
The Source and Share Tree models are the working model of how the tree is built; all multicast routing protocols fit into one or both. This is the 'theory' or model. PIM-DM's operational falls in the source tree model and PIM-SM is classified an

41. IOS command to configure router to be a member of an IGMP group or statically connected member.
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
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
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
Local preference Atomic Aggregate BGP

42. What is one mechanism that GURANTEES the BGP AS path is loop free?
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
The router will not accept a routing update that includes its AS number in the path. 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
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

43. What is a BGP route reflector - What is it purpose?
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword 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
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
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

44. Explain the way RR handles route updates.
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) 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
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 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

45. What command will produce the following output and What is it displaying? <img src='5d3c9233dd205ee4319ef0ac2fc07460.jpg' />
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. 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
The BGP Table Command = show ip bgp BGP
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP

46. What is one method involving minimal configuration to prevent and multi-homed BGP network from becoming a transit AS?
Links = n(n-1)/2 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
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

47. What is the full mesh versus partial mesh IBGP and What are the implications of each?
Links = n(n-1)/2 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. 
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
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP

48. What block of multicast MAC addresses belong to multicast?
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. 
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
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. 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' 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
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
AS-Path Next Hop Origin BGP
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

50. What is a BGP black hole and how is it avoided?
EBGP = 20 iBGP = 200 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
Links = n(n-1)/2 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