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

1. Explain the AS format and ranges?
Local preference<br />Atomic Aggregate BGP
Default-Network<br />Static route<br /> BGP
Efficiency<br />Performance<br />Scalability with applications<br /> Multicast
16 bit number 1 to 65535<br />1-64511: Public AS<br />64512-6535: Reserved for private AS<br /> BGP


2. Explain the BGP route decision process? How many routes does it select? Where do they go? Where do the ones go that are not used?
Class D address space<br />First bits are ALWAYS 1110<br />224.0.0.0 - 239.255.255.255<br /> Multicast
BGP not designed for load balancing (by default). <br />BGP selected the SINGLE best path to a destination and places it in the routing table; the rest are kept in the BGP Table.<br />Paths are chosen based on policy. BGP eliminates paths until one p
OT<br />Allows the router to 'tag' and thus implement policy based on this tag.<br /> BGP
The router will not accept a routing update that includes its AS number in the path. BGP


3. Describe how and IGMPv2 host leaves. What is the interaction between host and router look like?
Loopback more resilient than physical interfaces. BGP
Bidirection PIM mode - designed for many to many applications.<br />Source Specific Multicast (SSM) ; builds only source specific shortest path trees.<br /> Multicast
Rule: Router must be known by an IGP before it may be advertised by BGP peers.<br />Prevents 'blackholes' when AS is a transit network and not all speaker are running BGP<br />Should be left on it AS is a transit AS and not all routers run BGP.<br />
Sends a leave message to 224.0.0.2<br />Router then sends a group specific query<br />Remaining member(s) send a report so group remains active.<br /> Multicast


4. Name to enhancements to PIM.
1. Weight - Administrative preference (Highest)<br /><br />2. Local Preference - Communicated between peers within AS (Highest)<br /><br />3. Self-originated - Prefer path originated locally (True)<br /><br />4. AS Path - Minimize AS hops (Shortest)<
Bidirection PIM mode - designed for many to many applications.<br />Source Specific Multicast (SSM) ; builds only source specific shortest path trees.<br /> Multicast
When AS has more than one connection to the Internet it is called multihoming.<br />Inbound reliability<br />Better performance by selecting more optimal paths<br />Multihoming can be to one ISP or to several.<br /> BGP
IANA delegates to Regional Internet Registries (RIRs):<br />ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC<br /> BGP


5. State how IGMPv1 operates.
16 bit number 1 to 65535<br />1-64511: Public AS<br />64512-6535: Reserved for private AS<br /> BGP
Default-Network<br />Static route<br /> BGP
Rule: Router must be known by an IGP before it may be advertised by BGP peers.<br />Prevents 'blackholes' when AS is a transit network and not all speaker are running BGP<br />Should be left on it AS is a transit AS and not all routers run BGP.<br />
RFC 1112<br />Sends membership query every 60 - 120 seconds to 224.0.0.1<br />Hosts send membership report in response to the query<br /> Multicast


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

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7. What are the 6 BGP Neighbor states?
One-to-many: video distribution<br />Many-to-many: Collaboration<br />Many-to-one: auction - polling or data collection<br />Few-to-many: auction - polling or data collection<br /> Multicast
Idle - Router looking in routing table to see if route exists to neighbor. <br /><br />[Active - When no response to Open message] <br /><br />Connect - Router found route to neighbor and has performed the TCP three-way handshake<br /><br />Open Sent
Loopback more resilient than physical interfaces. BGP
AS-Path<br />Next Hop<br />Origin BGP


8. Explain the Local Preference attribute.<br />

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9. What are the 3 BGP tables and What is in them?
BGP Table - BGP topology database - information <br />BGP Neighbor Table - list of connected neighbors<br />IP Routing Table - Duh.<br /> BGP
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
1. Weight - Administrative preference (Highest)<br /><br />2. Local Preference - Communicated between peers within AS (Highest)<br /><br />3. Self-originated - Prefer path originated locally (True)<br /><br />4. AS Path - Minimize AS hops (Shortest)<
The unicast routing table.<br />No routing updates are sent between PIM routers.<br /> Multicast


10. How does a host learn about available multicast streams?
Class D address space<br />First bits are ALWAYS 1110<br />224.0.0.0 - 239.255.255.255<br /> Multicast
Cisco Proprietary - between router and switch<br />'Client/Server': Router = CGMP Server - Switch = CGMP Client<br />When router sees IGMP control message it creates a CGMP packet with the mutlicast MAC + client MAC; sends this to 'All CGMP Devices M
Routes learned through IBPG are never propogated to other IBGP speakers.<br /><br />This is a loop prevention mechanism. BGP
Well know predefined group<br />Directory - sd / SDP<br />Webpage/URL<br />Email link<br /> Multicast


11. 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
Router(config-router)# neighbor 192.168.1.1 remote-as 65000<br />Router(config-router)# neighbor 192.168.1.1 route-reflector-client<br /> BGP
Most applications rely on UDP<br />Security issues<br />Out of order delivery &amp; duplicate packets are a possibility during topology changes.<br />Lack of windowing/congestion control.<br /> Multicast
Links = n(n-1)/2 BGP


12. Describe how PIM-SM operates.
The is the multicast bit. Multicast
RFC 2362<br />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.<br />Last hop routers to receiver knows the group RP IP address and sends a (* -G) join toward
When using the <span style='font-style:italic;'>classful</span> method - at least one subnet of the classful range must reside in the IP routing table.<br /><br />When using the <span style='font-style:italic;'>classless</span> method the exact subne
RFC 1112<br />Sends membership query every 60 - 120 seconds to 224.0.0.1<br />Hosts send membership report in response to the query<br /> Multicast


13. Explain the Community attribute.

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14. 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.<br />Inbound reliability<br />Better performance by selecting more optimal paths<br />Multihoming can be to one ISP or to several.<br /> BGP
When using the <span style='font-style:italic;'>classful</span> method - at least one subnet of the classful range must reside in the IP routing table.<br /><br />When using the <span style='font-style:italic;'>classless</span> method the exact subne
R1(config-router)#neighbor MyPeers peer-group<br />R1(config-router)#neighbor 10.1.1.1 remote-as 64513<br />R1(config-router)#neighbor 10.1.1.1 peer-group MyPeers<br /> BGP
EBGP will only peer to direclty connected neighbors and a loopback is considered one hop away.<br /><br />With eBGP peering to a loopback you must enable eBGP Multihop.<br /><br />R1(config-router)# neighbor 192.168.1.1 ebgp-multihop 2 BGP


15. 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.<br />Shared distribution tree state entries (* -G) consume less CPU but may take suboptimal path to receiver.<br /> Multicast
Partial mesh iBPG is where not all BGP speaks within and AS have an established neighbor relationship. <br />Full mesh is every BGP speaker has a neighbor (peer) with each other. <br />Routing updates are not replcated in iBPG the peers do not pass i
Dense mode interfaces are always added to the table. <br /><br />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<br /> Multi
AS-Path<br />Next Hop<br />Origin BGP


16. What effect will placing a route to null0 have on BGP?
R2(config)# access-list 1 permit 192.168.0.0 0.0.0.255<br />R1(config-router)# neighbor 10.1.1.1 distribute-list 1 out<br />R1(config-router)# neighbor 10.1.1.2 distribute-list 1 out<br /> BGP
BPG will find an exact match. BGP
Contains information on ONE path only<br /><br />Withdrawn routes - List of IP prefixes for routes being withdrawn.<br />Path attributes - AS-Path - etc.<br />Network layer reachability information - List of IP prefixes reachable by this path. BGP
The is the multicast bit. Multicast


17. What are the 4 categories of BGP attributes and what do they mean?
OT<br />Allows the router to 'tag' and thus implement policy based on this tag.<br /> BGP
Well-known Mandatory - Must be supported and propagated.<br />Well-known Discretionary - Must be supported; propagation optional.<br />Optional Transitive - Marked as partial if unsupported by neighbor.<br />Option Nontransitive - Deleted is unsuppor
Router#show ip igmp group<br />Group address - interface - uptime - expires - and last reporter.<br /> Multicast
16 bit number 1 to 65535<br />1-64511: Public AS<br />64512-6535: Reserved for private AS<br /> BGP


18. What are three different common ways to perform BGP multihoming with regard to routing table?
EBGP = 20<br />iBGP = 200<br /> BGP
Router(config-router)# neighbor 192.168.1.1 remote-as 65000<br />Router(config-router)# neighbor 192.168.1.1 route-reflector-client<br /> BGP
Rule: Router must be known by an IGP before it may be advertised by BGP peers.<br />Prevents 'blackholes' when AS is a transit network and not all speaker are running BGP<br />Should be left on it AS is a transit AS and not all routers run BGP.<br />
ISP passes only default route to AS.<br />ISP passes default route and provider owned select routes to AS.<br />ISP passes all routes to AS.<br /> BGP


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

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

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21. 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. <br />RR allow the propagation of routes learned by IBGP to other IBGP peers without having a full mesh of IBGP
1. Weight - Administrative preference (Highest)<br /><br />2. Local Preference - Communicated between peers within AS (Highest)<br /><br />3. Self-originated - Prefer path originated locally (True)<br /><br />4. AS Path - Minimize AS hops (Shortest)<
Dense mode interfaces are always added to the table. <br /><br />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<br /> Multi


22. What is the key difference between how a multicast routing protocol forwards packets versus a unicast routing protocol?
Must insure loopback is reachable in the routing table. BGP
Use loopback interface to establish the neighbor. (i.e. peer to a loopback interface)<br />Tell BGP to use the lookback interface as teh source of updates<br /><br />R1(config-router)# neighbor 192.168.1.1 update-source loopback0<br /> BGP
Unicast uses a routing table looking and forwards towards the destination address.<br />Multicast forwards out multiple interfaces and away from the source and towards multiple destinations using a distribution tree.<br /> Multicast
RFC 1112<br />Sends membership query every 60 - 120 seconds to 224.0.0.1<br />Hosts send membership report in response to the query<br /> Multicast


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

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24. Explain CGMP.

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25. What is the command to configure a BGP RR?<br />
Cluster - combination of RR and its clients. Can have multiple clusters in an AS. <br />Originator ID - carries router ID of the route's originator<br />Cluster ID - configured when multiple RR in a cluster.<br />Cluster list - sequence of cluster ID
RFC - 3376<br />Ability to filter multicast source (can be picky)<br />IGMPv3 membership report goes to 224.0.0.22 and may include the multicast hosts it will accept or deny.<br /> Multicast
Router(config-router)# neighbor 192.168.1.1 remote-as 65000<br />Router(config-router)# neighbor 192.168.1.1 route-reflector-client<br /> BGP
SPT (S -G) consume more memory because there is an entry for each source BUT traffic is sent over optimal path to receiver.<br />Shared distribution tree state entries (* -G) consume less CPU but may take suboptimal path to receiver.<br /> Multicast


26. What entities are responsible for allocating BGP AS numbers?
IANA delegates to Regional Internet Registries (RIRs):<br />ARIN - AfriNIC - APNIC - LACNIC and RIPE NCC<br /> BGP
224.0.0.1 - All systems<br />224.0.0.2 - All routers<br />224.0.0.4 - DVMRP routers<br />224.0.0.5 - All OSPF<br />224.0.0.6 - All OSPF DR<br />224.0.0.9 - RIP v2 routers<br />224.0.0.10 - EIGRP routers<br />224.0.0.13 - PIM routers<br />224.0.0.15 -
R1(config-router)# neighbor 192.168.1.1 next-hop-self<br /><br />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.<br /><br />
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP


27. What does BGP use for communication? What advantage does it offer?
AS-Path<br />Next Hop<br />Origin BGP
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP
RFC 1112<br />Sends membership query every 60 - 120 seconds to 224.0.0.1<br />Hosts send membership report in response to the query<br /> Multicast
TCP port 179<br />Reliability; uses sliding window<br />Triggered - incremental updates made very efficient<br /> BGP


28. What does a 0.0.0.0 signify in the Next Hop column in the BGP Table?
Using a Distribute List to filter outbound routing updates. BGP
Default-Network<br />Static route<br /> BGP
This router originated the route. 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.<br />PIM-DM's operational falls in the source tree model and PIM-SM is classified an


29. Within the layer 3 multicast address space - name 3 reserved scopes and their purpose.
'Periodic Flood and Prune.'<br />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.<br />Prune messages are sent on all non-RPF interfaces and RPF int
Local scoped: 224.0.0.0 - 224.0.0.255<br />TTL of 1; Never to leave local network - for routing protocols and other network maintenance.<br />Global scoped: 224.0.1.0 - 238.255.255.255<br />MBone dynamically allocate throughout Internet<br />Limited/
This will advertise the entire classful network:<br />R1(config-router)# network 10.1.1.0<br /><br />This will advertise the the classless network:<br />R1(config-router)# network 10.1.1.0 mask 255.255.255.0<br /><br /> BGP
BGP specifies that it can advertise to its peers in neighboring AS's only routes that it uses.<br />BGP cannot influence how a neighboring AS will route your traffic BUT it can influence how your traffic gets to the neighboring AS. <br /> BGP


30. Explain the Weight attribute.
O<br />Cisco only.<br />Routes with higher weight are preferred (0 - 65535) . Paths that the router originates have 32768; other paths have default of 0.<br /> BGP
BPG will find an exact match. BGP
RFC 2236<br />Leave and join latency resolved<br />Group specific query to G instead of 224.0.0.1<br />Leave group message<br />Election of querier (lowest IP) on broadcast medium with multiple routers <br /> Multicast
Cluster - combination of RR and its clients. Can have multiple clusters in an AS. <br />Originator ID - carries router ID of the route's originator<br />Cluster ID - configured when multiple RR in a cluster.<br />Cluster list - sequence of cluster ID


31. What are the basic commands to enable BGP - define a BGP peer relationship and advertise a network?
One-to-many: video distribution<br />Many-to-many: Collaboration<br />Many-to-one: auction - polling or data collection<br />Few-to-many: auction - polling or data collection<br /> Multicast
Using a Distribute List to filter outbound routing updates. BGP
Variable length sequence of path attributes<br />Attribute Type -1 byte flag field - 1 byte type code<br />Attribute Length <br />Attribute Value<br />Attribute flag field = 0000 0000<br />W | O - T | N - P | C<br /> BGP
Router#(config) router bgp 1<br />Router#(config-router) neighbor 192.168.1.1 remote-as 1<br />Router#(config-router) network 192.168.0. mask 255.255.255.0<br /> BGP


32. IOS command to dictate when a leaf router (in PIM-SM) will switch from shared to source tree.
ON<br />Displayed as metric in Cisco IOS; lower is preferred. Default is 0. Indicated to external AS the preferred path into the AS.<br />'Influence inbound traffic to an AS'<br />By default ONLY compares if neighbors AS is same for all routes being
MOSPF<br />DVMRP<br />CBT<br />PIM Dense Mode<br />PIM Sparse Mode<br />PIM Sparse-Dense Mode<br /> Multicast
Language between local router interface and hosts.<br />IGMP - ICMP - similarities <br />TTL is usually 1; RFC states it should never leave local subnet.<br />Creates and maintains group membership for hosts wishing to participate in a multicast grou
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast


33. Name the Well-known discretionary attributes.
Most applications rely on UDP<br />Security issues<br />Out of order delivery &amp; duplicate packets are a possibility during topology changes.<br />Lack of windowing/congestion control.<br /> Multicast
TCP port 179<br />Reliability; uses sliding window<br />Triggered - incremental updates made very efficient<br /> BGP
EBGP will only peer to direclty connected neighbors and a loopback is considered one hop away.<br /><br />With eBGP peering to a loopback you must enable eBGP Multihop.<br /><br />R1(config-router)# neighbor 192.168.1.1 ebgp-multihop 2 BGP
Local preference<br />Atomic Aggregate BGP


34. What is the full mesh versus partial mesh IBGP and What are the implications of each?
AS-Path<br />Next Hop<br />Origin BGP
Partial mesh iBPG is where not all BGP speaks within and AS have an established neighbor relationship. <br />Full mesh is every BGP speaker has a neighbor (peer) with each other. <br />Routing updates are not replcated in iBPG the peers do not pass i
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
RFC - 3376<br />Ability to filter multicast source (can be picky)<br />IGMPv3 membership report goes to 224.0.0.22 and may include the multicast hosts it will accept or deny.<br /> Multicast


35. What is the IOS command to check for IGMP group members? What info does it reveal?
Routes learned through IBPG are never propogated to other IBGP speakers.<br /><br />This is a loop prevention mechanism. BGP
Using a Distribute List to filter outbound routing updates. BGP
Router#show ip igmp group<br />Group address - interface - uptime - expires - and last reporter.<br /> Multicast
1. Weight - Administrative preference (Highest)<br /><br />2. Local Preference - Communicated between peers within AS (Highest)<br /><br />3. Self-originated - Prefer path originated locally (True)<br /><br />4. AS Path - Minimize AS hops (Shortest)<


36. What does a '*' and '&gt;' mean in the BGP table?
Router#show ip igmp interface fa0/0<br /> Multicast
Sends a leave message to 224.0.0.2<br />Router then sends a group specific query<br />Remaining member(s) send a report so group remains active.<br /> Multicast
* = Best route<br />&gt; = Route has been inserted into the routing table<br /> BGP
This should only be for ISP's<br />An improperly configured AS (that is not meant to be a transit) could inadvertently become one.<br /> BGP


37. What are 2 stipulations of advertising networks BGP?

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38. What is the difference between iBGP and eBGP?
Cluster - combination of RR and its clients. Can have multiple clusters in an AS. <br />Originator ID - carries router ID of the route's originator<br />Cluster ID - configured when multiple RR in a cluster.<br />Cluster list - sequence of cluster ID
Session description &amp; announcement.<br />Transport session announcement via 224.2.127.254.<br />Creation of new sessions.<br /> 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
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP


39. Name 4 verification commands for BGP and what they display?
Partial mesh iBPG is where not all BGP speaks within and AS have an established neighbor relationship. <br />Full mesh is every BGP speaker has a neighbor (peer) with each other. <br />Routing updates are not replcated in iBPG the peers do not pass i
OT<br />Allows the router to 'tag' and thus implement policy based on this tag.<br /> BGP
Show ip bgp - Shows entire BGP topology database (BGP table)<br /><br />show ip bgp rib-failure - Displays BGP routes not installd into the routing information base (RIB) and reason they were not installed.<br /><br />show ip bgp neighbors - Displays
'Periodic Flood and Prune.'<br />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.<br />Prune messages are sent on all non-RPF interfaces and RPF int


40. What special consideration is there when peering to a eBGP neighbor using a loopback? What is the solution to this?
Local preference<br />Atomic Aggregate BGP
EBGP will only peer to direclty connected neighbors and a loopback is considered one hop away.<br /><br />With eBGP peering to a loopback you must enable eBGP Multihop.<br /><br />R1(config-router)# neighbor 192.168.1.1 ebgp-multihop 2 BGP
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP
AS-Path<br />Next Hop<br />Origin BGP


41. Which IOS command shows what version of IGMP is running?
Router#show ip igmp interface fa0/0<br /> Multicast
Contains information on ONE path only<br /><br />Withdrawn routes - List of IP prefixes for routes being withdrawn.<br />Path attributes - AS-Path - etc.<br />Network layer reachability information - List of IP prefixes reachable by this path. BGP
R1(config-router)# neighbor 192.168.1.1 next-hop-self<br /><br />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.<br /><br />
'Periodic Flood and Prune.'<br />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.<br />Prune messages are sent on all non-RPF interfaces and RPF int


42. Explain the path selection process for BGP? What is the order and what preference does it take?
Determines upstream and downstream interfaces.<br />Uses the unicast routing table to insure that only one interface is considered to be and incoming interface for the source.<br />RPF makes sure that if data is looped around is not forwarded. <br />
Links = n(n-1)/2 BGP
RFC - 3376<br />Ability to filter multicast source (can be picky)<br />IGMPv3 membership report goes to 224.0.0.22 and may include the multicast hosts it will accept or deny.<br /> Multicast
1. Weight - Administrative preference (Highest)<br /><br />2. Local Preference - Communicated between peers within AS (Highest)<br /><br />3. Self-originated - Prefer path originated locally (True)<br /><br />4. AS Path - Minimize AS hops (Shortest)<


43. How is the BGP network command differ from IGP's?
It actually determines which networks are advertised. BGP
BGP specifies that it can advertise to its peers in neighboring AS's only routes that it uses.<br />BGP cannot influence how a neighboring AS will route your traffic BUT it can influence how your traffic gets to the neighboring AS. <br /> BGP
R1(config-router)#neighbor 192.168.1.1 password MyPassword<br /><br />OR<br /><br />R1(config-router)#neighbor MyPeerGroup password MyPassword<br /> BGP
Well-known Mandatory - Must be supported and propagated.<br />Well-known Discretionary - Must be supported; propagation optional.<br />Optional Transitive - Marked as partial if unsupported by neighbor.<br />Option Nontransitive - Deleted is unsuppor


44. What does PIM use for its multicast routing calculations?
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
Router(config-router)# neighbor 192.168.1.1 remote-as 65000<br />Router(config-router)# neighbor 192.168.1.1 route-reflector-client<br /> BGP
Language between local router interface and hosts.<br />IGMP - ICMP - similarities <br />TTL is usually 1; RFC states it should never leave local subnet.<br />Creates and maintains group membership for hosts wishing to participate in a multicast grou
The unicast routing table.<br />No routing updates are sent between PIM routers.<br /> Multicast


45. What is a neighbor call in BGP?
BGP peer BGP
MOSPF<br />DVMRP<br />CBT<br />PIM Dense Mode<br />PIM Sparse Mode<br />PIM Sparse-Dense Mode<br /> Multicast
Sends a leave message to 224.0.0.2<br />Router then sends a group specific query<br />Remaining member(s) send a report so group remains active.<br /> Multicast
Router(config-router)# neighbor 192.168.1.1 remote-as 65000<br />Router(config-router)# neighbor 192.168.1.1 route-reflector-client<br /> BGP


46. IOS command to configure router to be a member of an IGMP group or statically connected member.
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
Member of a group:<br />Router#(config) ip igmp join-group group-address<br />Statically connected:<br />Router#(config) ip igmp join-group group-address<br />In this mode router forwards (fast switches) group packets but itself does not accept group
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). <br />Shared Tree - Single tree that is shared between all sources; single common root called the rendezvous p
Local preference<br />Atomic Aggregate BGP


47. What are two methods of establishing a gateway of last resort?
Language between local router interface and hosts.<br />IGMP - ICMP - similarities <br />TTL is usually 1; RFC states it should never leave local subnet.<br />Creates and maintains group membership for hosts wishing to participate in a multicast grou
When AS has more than one connection to the Internet it is called multihoming.<br />Inbound reliability<br />Better performance by selecting more optimal paths<br />Multihoming can be to one ISP or to several.<br /> BGP
Default-Network<br />Static route<br /> BGP
Bidirection PIM mode - designed for many to many applications.<br />Source Specific Multicast (SSM) ; builds only source specific shortest path trees.<br /> Multicast


48. Explain the concept of RPF.
The is the multicast bit. Multicast
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP
Reverse Path Forwarding is the forwarding logic multicast of multicast. <br />It is the opposite of unicast in that is forwards AWAY from source as opposed to towards the receiver.<br /> Multicast
Local scoped: 224.0.0.0 - 224.0.0.255<br />TTL of 1; Never to leave local network - for routing protocols and other network maintenance.<br />Global scoped: 224.0.1.0 - 238.255.255.255<br />MBone dynamically allocate throughout Internet<br />Limited/


49. What command used to perform the following:<br />A) Reset all neighbors session ('bounce')<br />B) Soft inbound reset<br />C) Soft outbound reset<br />D) Soft inbound reset of neighbor 10.1.1.1<br /><br />R1# clear ip bgp <br />R1# clear ip bgp soft
R1# clear ip bgp <br />R1# clear ip bgp soft in<br />R1# clear ip bgp * soft out<br />R1# clear ip bgp 10.1.1.1 soft in<br /><br /> BGP
Open - Version - AS - Hold Time - BGP Router ID - Optional Parameters<br />Keepalive - Sent every 60 seconds by default; hold time 180 Seconds.<br />Update - Information on only ONE path; <br />Notification - When error condition detected<br /> 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). <br />Shared Tree - Single tree that is shared between all sources; single common root called the rendezvous p
One-to-many: video distribution<br />Many-to-many: Collaboration<br />Many-to-one: auction - polling or data collection<br />Few-to-many: auction - polling or data collection<br /> Multicast


50. 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)<br />Tell BGP to use the lookback interface as teh source of updates<br /><br />R1(config-router)# neighbor 192.168.1.1 update-source loopback0<br /> BGP
IGMP Snooping - requires special ASICS can degrade performance with it; is supported by multiple vendors.<br />CGMP - Cisco proprietary - only work on Cisco hardware; resource friendly<br />GMRP - Replaced by MRP; obscure<br />Manually - Performance
WM<br />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.<br />in IBGP the next hop advertised by EBGP should
This should only be for ISP's<br />An improperly configured AS (that is not meant to be a transit) could inadvertently become one.<br /> BGP