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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 one mechanism that GURANTEES the BGP AS path is loop free?
The router will not accept a routing update that includes its AS number in the path. 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
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC 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

2. What does a '*' and '>' mean in the BGP table?
* = Best route > = Route has been inserted into the routing table 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
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP
Loopback more resilient than physical interfaces. BGP

3. What is the command to enable BPG authentication?
AS-Path Next Hop Origin BGP
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword 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
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast

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

5. What does PIM use for its multicast routing calculations?
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' No routing updates are sent between PIM routers. Multicast
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
AS-Path Next Hop Origin BGP

6. IOS command to dictate when a leaf router (in PIM-SM) will switch from shared to source tree.
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP
It actually determines which networks are advertised. 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
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast

7. What advantage is there it establishing a neighbor relationship using a loopback interface?
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast
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
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)<
Loopback more resilient than physical interfaces. BGP

8. 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
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
BPG will find an exact match. BGP

9. 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
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
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. 
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' Uses BGP attributes are the 'metric'. Path it decides it based on 'hops' where hop is Autonomous Systems. BGP
The is the multicast bit. 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
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. 

11. What is the difference between iBGP and eBGP?
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)<
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast

12. What special consideration is there when peering to a eBGP neighbor using a loopback? What is the solution to this?
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
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
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
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

13. Explain the Local Preference attribute. 

14. What command used to perform the following: A) Reset all neighbors session ('bounce') B) Soft inbound reset C) Soft outbound reset D) Soft inbound reset of neighbor 10.1.1.1 R1# clear ip bgp R1# clear ip bgp soft
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
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
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<br
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

15. Explain CGMP.

16. What does the 'maximum-paths router' command facilitate?
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
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
It actually determines which networks are advertised. 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

17. State 3 functions SDR performs?
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast
OT Allows the router to 'tag' and thus implement policy based on this tag. BGP
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] 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

18. Within the layer 3 multicast address space - name 3 reserved scopes and their purpose.
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/
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
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP

19. Describe how PIM-Sparse-Dense operates.

20. What is a neighbor call in 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
BGP peer BGP
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client 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

21. 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?
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
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
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast

22. What does a 0.0.0.0 signify in the Next Hop column in the BGP Table?
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 = 20 iBGP = 200 BGP
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. Multicast
This router originated the route. BGP

23. What are some of the obstacles with IGMP and multicast in general as it relates to layer 2/switches?
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
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. 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
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

24. Which IOS command shows what version of IGMP is running?
R1(config-router)#neighbor 192.168.1.1 password MyPassword OR R1(config-router)#neighbor MyPeerGroup password MyPassword BGP
Router#show ip igmp interface fa0/0 Multicast
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast

25. Explain the contents of the BGP update message.
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
Must insure loopback is reachable in 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
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

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

27. Explain the AS-Path attribute.

28. Explain the concept of RPF.
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
16 bit number 1 to 65535 1-64511: Public AS 64512-6535: Reserved for private AS BGP
Efficiency Performance Scalability with applications Multicast
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

29. What is the significance of an AS being a transit AS?

30. What is a BGP peer group?

31. What is the layer 2 multicast address and how is it formed? What potential problem is there with this?
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast
The neighbor expects to see the updates from the source address configured in the neighbor statement. 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 (* -G) - 'Star comma G'; Any source sending to the group. Traffic forwar

32. 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
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
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
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

33. What is a BGP route reflector - What is it purpose?
The router will not accept a routing update that includes its AS number in the path. 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
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 peer BGP

34. What is the multicast IP address space?
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
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 Multicast
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
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

35. What entities are responsible for allocating BGP AS numbers?
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 -
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. 
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
IANA delegates to Regional Internet Registries (RIRs): ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC BGP

36. Explain what role IGMP plays.
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
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
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
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

37. 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
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
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
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast

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

39. What are the administrative distances of eBGP and iBGP?
Router#show ip igmp group Group address - interface - uptime - expires - and last reporter. Multicast
EBGP = 20 iBGP = 200 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. 
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

40. Explain the path selection process for BGP? What is the order and what preference does it take?
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient 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)<
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast
RFC 1112 Sends membership query every 60 - 120 seconds to 224.0.0.1 Hosts send membership report in response to the query Multicast

41. What are some disadvantages of 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
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
The is the multicast bit. Multicast
<img src='9618cf01b9422f541fc213b74a3bd9de.png' /> Multicast

42. What is the terminology for BGP route reflector?

43. What is one method involving minimal configuration to prevent and multi-homed BGP network from becoming a transit AS?
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
Places it in the routing table. BGP
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP
Using a Distribute List to filter outbound routing updates. BGP

44. How is the BGP network command differ from IGP's?
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
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
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
It actually determines which networks are advertised. BGP

45. Explain the Community attribute.

46. Explain the IGMPv3 membership process and new features.
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#show ip igmp group Group address - interface - uptime - expires - and last reporter. Multicast
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
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast

47. What are the basic commands to enable BGP - define a BGP peer relationship and advertise a network?
Efficiency Performance Scalability with applications Multicast
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. 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
Loopback more resilient than physical interfaces. BGP

48. What is the formula to determine number of links in a full mesh topology?
Links = n(n-1)/2 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
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
Class D address space First bits are ALWAYS 1110 224.0.0.0 - 239.255.255.255 Multicast

49. What type of protocol is BGP classified as? What is its decision engine?

50. What is the signifigance of the neighbor address when establishing BGP neighbor in the context of network that has multiple paths to the neighbor?
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' Directory - sd / SDP Webpage/URL Email link Multicast
The neighbor expects to see the updates from the source address configured in the neighbor statement. 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