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

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2. What does IGMPv2 add?
Local preference Atomic Aggregate BGP
BPG will find an exact match. BGP
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
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

3. What is the significance of the 8th bit in the MAC address?
The is the multicast bit. Multicast
This router originated the route. BGP
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP

4. Explain the Weight attribute.
'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
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
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP

5. Explain the MED attribute.

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6. After the path selection process - What does BGP do with the route?
The unicast routing table. No routing updates are sent between PIM routers. 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
This should only be for ISP's An improperly configured AS (that is not meant to be a transit) could inadvertently become one. BGP
Places it in the routing table. BGP

7. Explain the way RR handles route updates.
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client 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/
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
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

8. IOS command to configure a rendezvous point .
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list 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
BPG will find an exact match. BGP
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast

9. What entities are responsible for allocating BGP AS numbers?
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC 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. 
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
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast

10. What special consideration is there when peering to a eBGP neighbor using a loopback? What is the solution to this?
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
<img src='9618cf01b9422f541fc213b74a3bd9de.png' /> 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
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP

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

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12. What are three different common ways to perform BGP multihoming with regard to routing table?
Router#show ip igmp interface fa0/0 Multicast
Links = n(n-1)/2 BGP
The unicast routing table. No routing updates are sent between PIM routers. 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

13. Within the layer 3 multicast address space - name 3 reserved scopes and their purpose.
The is the multicast bit. Multicast
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] 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/
(S -G) - 'S comma G'; Source sending to the group. Typically reflect a source tree but can appear on a shared tree. Traffic forwarded via the shortest path from the source. (* -G) - 'Star comma G'; Any source sending to the group. Traffic forwar

14. 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?
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
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
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
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. 

15. When creating a BGP neighbor relationship to a loopback interface what must be remember in the context of routing?
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
Must insure loopback is reachable in the routing table. 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
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

16. Describe how PIM-DM operates.

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17. What is the key difference between how a multicast routing protocol forwards packets versus a unicast routing protocol?
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
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
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' 2. Local Preference - Communicated between peers within AS (Highest) 3. Self-originated - Prefer path originated locally (True) 4. AS Path - Minimize AS hops (Shortest)<

18. What is the command to enable BPG authentication?
Loopback more resilient than physical interfaces. BGP
Default-Network Static route BGP
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword 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

19. Explain CGMP.

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20. Explain the Community attribute.

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21. Explain the AS-Path attribute.

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22. Explain the multicast routing table distribution tree notations.

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23. Explain the AS format and ranges?
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
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
16 bit number 1 to 65535 1-64511: Public AS 64512-6535: Reserved for private AS BGP
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. What command will produce the following output and What is it displaying? <img src='5d3c9233dd205ee4319ef0ac2fc07460.jpg' />
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
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
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
The BGP Table Command = show ip bgp BGP

25. What is a BGP black hole and how is it avoided?
The is the multicast bit. 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 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
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. 

26. What is the command to configure a BGP RR? 
Links = n(n-1)/2 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)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client 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

27. How does a host learn about available multicast streams?
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
Well know predefined group Directory - sd / SDP Webpage/URL Email link Multicast
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP
(S -G) - 'S comma G'; Source sending to the group. Typically reflect a source tree but can appear on a shared tree. Traffic forwarded via the shortest path from the source. (* -G) - 'Star comma G'; Any source sending to the group. Traffic forwar

28. Describe 4 multicast application models and give an example of each?
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
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
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
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

29. What is BGP multihoming and why would you want to do it?
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
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
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
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. 

30. What are the methods to control multicast within the layer 2 domain? What are some benefits & drawbacks of each?
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
The is the multicast bit. 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
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

31. Describe how and IGMPv2 host leaves. What is the interaction between host and router look like?
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
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 neighbor expects to see the updates from the source address configured in the neighbor statement. 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

32. Explain the path selection process for BGP? What is the order and what preference does it take?
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
Router#show ip igmp interface fa0/0 Multicast
Local preference Atomic Aggregate 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)<

33. Which IOS command shows what version of IGMP is running?
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
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
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP
Router#show ip igmp interface fa0/0 Multicast

34. What are two methods of establishing a gateway of last resort?
Default-Network Static route BGP
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP
Using a Distribute List to filter outbound routing updates. 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

35. 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
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
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
AS-Path Next Hop Origin BGP

36. What is the layer 2 multicast address and how is it formed? What potential problem is there with this?
Router#show ip igmp interface fa0/0 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 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' It is the opposite of unicast in that is forwards AWAY from source as opposed to towards the receiver. Multicast

37. What are the 4 categories of BGP attributes and what do they mean?
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
Well-known Mandatory - Must be supported and propagated. Well-known Discretionary - Must be supported; propagation optional. Optional Transitive - Marked as partial if unsupported by neighbor. Option Nontransitive - Deleted is unsuppor
Must insure loopback is reachable in the routing table. BGP
Efficiency Performance Scalability with applications Multicast

38. What is one mechanism that GURANTEES the BGP AS path is loop free?
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. 
Well know predefined group Directory - sd / SDP Webpage/URL Email link Multicast
The router will not accept a routing update that includes its AS number in the path. 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

39. What is the multicast IP address space?
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
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 Multicast
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
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

40. What is the terminology for BGP route reflector?

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

42. What is a BGP peer group?

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43. Name to enhancements to PIM.
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
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
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
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast

44. How is the BGP network command differ from IGP's?
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
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
It actually determines which networks are advertised. BGP
The router will not accept a routing update that includes its AS number in the path. BGP

45. State how IGMPv1 operates.
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
RFC 1112 Sends membership query every 60 - 120 seconds to 224.0.0.1 Hosts send membership report in response to the query 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

46. What are the commands to enable multicast routing on a router?
It actually determines which networks are advertised. BGP
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
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
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

47. Explain the Origin attribute.

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48. What are the two multicast distribution tree types models and differences?

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49. Name 4 verification commands for BGP and what they display?
Must insure loopback is reachable in the routing table. 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
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP
Links = n(n-1)/2 BGP

50. 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.
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
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. 
Default-Network Static 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