CCNP

Instructions:

• Answer 50 questions in 15 minutes.
• If you are not ready to take this test, you can study here.
• Match each statement with the correct term.
• Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

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. IOS command to configure a rendezvous point .
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
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
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast


2. Name several common local scoped multicast addresses and their purpose.
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 -
BPG will find an exact match. BGP
OT<br />Allows the router to 'tag' and thus implement policy based on this tag.<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


3. What is the IBGP Split Horizon rule? What does this accomplish?
Routes learned through IBPG are never propogated to other IBGP speakers.<br /><br />This is a loop prevention mechanism. BGP
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
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
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


4. Describe how PIM-SM operates.
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 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
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
Local preference<br />Atomic Aggregate BGP


5. What does IGMPv2 add?
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
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
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast
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


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

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7. State how IGMPv1 operates.
<img src='9618cf01b9422f541fc213b74a3bd9de.png' /> 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
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
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 -


8. Name 6 multicast routing protocols.
MOSPF<br />DVMRP<br />CBT<br />PIM Dense Mode<br />PIM Sparse Mode<br />PIM Sparse-Dense Mode<br /> Multicast
The BGP Table<br /><br />Command = show ip bgp BGP
OT<br />Allows the router to 'tag' and thus implement policy based on this tag.<br /> BGP
WM<br />One of three values: <br />IGP - Route is interior to the originating AS. (BGP table shows 'i')<br />EGP - Route learned via EGP. (BGP table shows 'e')<br />Incomplete - Routes origin is unknown - usually when redistributed. (BGP table shows


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


10. What is the multicast IP address space?
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
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)<
Class D address space<br />First bits are ALWAYS 1110<br />224.0.0.0 - 239.255.255.255<br /> Multicast
Using a Distribute List to filter outbound routing updates. BGP


11. How does RPF avoid routing loops?
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
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 />
This router originated the route. BGP
Router#show ip igmp interface fa0/0<br /> Multicast


12. What effect will placing a route to null0 have on BGP?
Default-Network<br />Static route<br /> BGP
Router#show ip igmp interface fa0/0<br /> Multicast
BPG will find an exact match. BGP
Session description &amp; announcement.<br />Transport session announcement via 224.2.127.254.<br />Creation of new sessions.<br /> Multicast


13. Name the Well-known mandatory attributes.
AS-Path<br />Next Hop<br />Origin BGP
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
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
Bidirection PIM mode - designed for many to many applications.<br />Source Specific Multicast (SSM) ; builds only source specific shortest path trees.<br /> Multicast


14. IOS command to configure router to be a member of an IGMP group or statically connected member.
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
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
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
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


15. What is BGP multihoming and why would you want to do it?
Router#show ip igmp group<br />Group address - interface - uptime - expires - and last reporter.<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
Must insure loopback is reachable in the routing table. BGP
16 bit number 1 to 65535<br />1-64511: Public AS<br />64512-6535: Reserved for private AS<br /> BGP


16. Explain the methods of advertising networks in BGP.
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
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
The router will not accept a routing update that includes its AS number in the path. BGP
OT<br />Allows the router to 'tag' and thus implement policy based on this tag.<br /> BGP


17. What is the key difference between how a multicast routing protocol forwards packets versus a unicast routing protocol?
Router#show ip igmp group<br />Group address - interface - uptime - expires - and last reporter.<br /> Multicast
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
BPG will find an exact match. BGP


18. What are three different common ways to perform BGP multihoming with regard to routing table?
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
Group of BGP routers being configured that have the same update policy.<br />Similar to a 'template'; members then assigned to the peer group.<br /> BGP
The unicast routing table.<br />No routing updates are sent between PIM routers.<br /> Multicast
Links = n(n-1)/2 BGP


19. Name a significant inefficiency with IGMPv1.
Efficiency<br />Performance<br />Scalability with applications<br /> Multicast
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
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
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast


20. Explain the Next-Hop attribute. How does this differ from IGP's? In what environment might this be problematic?
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
WM<br /><br />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)'<br /><br />This insures a loop-free environment. If BGP receives a
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 neighbor expects to see the updates from the source address configured in the neighbor statement. BGP


21. Describe how PIM-Sparse-Dense operates.

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22. What is the full mesh versus partial mesh IBGP and What are the implications of each?
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
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
Well know predefined group<br />Directory - sd / SDP<br />Webpage/URL<br />Email link<br /> Multicast
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast


23. What block of multicast MAC addresses belong to multicast?
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. 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
Bidirection PIM mode - designed for many to many applications.<br />Source Specific Multicast (SSM) ; builds only source specific shortest path trees.<br /> Multicast
Router#show ip igmp group<br />Group address - interface - uptime - expires - and last reporter.<br /> Multicast


24. Explain the MED attribute.

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25. Explain the contents of the BGP update message.
Bidirection PIM mode - designed for many to many applications.<br />Source Specific Multicast (SSM) ; builds only source specific shortest path trees.<br /> Multicast
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
TCP port 179<br />Reliability; uses sliding window<br />Triggered - incremental updates made very efficient<br /> 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


26. Explain what role IGMP plays.
WM<br />One of three values: <br />IGP - Route is interior to the originating AS. (BGP table shows 'i')<br />EGP - Route learned via EGP. (BGP table shows 'e')<br />Incomplete - Routes origin is unknown - usually when redistributed. (BGP table shows
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] 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#show ip igmp interface fa0/0<br /> Multicast


27. What is one mechanism that GURANTEES the BGP AS path is loop free?
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
The router will not accept a routing update that includes its AS number in the path. BGP
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
AS-Path<br />Next Hop<br />Origin BGP


28. Describe how and IGMPv2 host leaves. What is the interaction between host and router look like?
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
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
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
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP


29. What is a BGP black hole and how is it avoided?
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
AS-Path<br />Next Hop<br />Origin 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
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 />


30. What is the formula to determine number of links in a full mesh topology?
Using a Distribute List to filter outbound routing updates. BGP
Links = n(n-1)/2 BGP
0100.5e00.0000 - 0100.5e7f.ffff - IANA reserved. 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


31. What are some disadvantages of 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
Group of BGP routers being configured that have the same update policy.<br />Similar to a 'template'; members then assigned to the peer group.<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
Update from client peer - sends update to all non-client peers and client peers except for originating peer.<br />Update from non-client peer - send update to all clients in the cluster.<br />Update from EBGP peer - update sent to all client peers an


32. What is the terminology for BGP route reflector?

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33. What command will produce the following output and What is it displaying?<br /><br /><img src='5d3c9233dd205ee4319ef0ac2fc07460.jpg' />
TCP port 179<br />Reliability; uses sliding window<br />Triggered - incremental updates made very efficient<br /> BGP
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
The BGP Table<br /><br />Command = show ip bgp 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


34. Explain CGMP.

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35. How does a host learn about available multicast streams?
Well know predefined group<br />Directory - sd / SDP<br />Webpage/URL<br />Email link<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 />
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
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


36. What is the command to configure a BGP RR?
Works if router has multiple parallel paths to a destination.<br />ONLY affect number of routes in IP routing table not the route selected at best in the BGP table.<br />Will load balance across equal cost paths in EGP session.<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
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
Places it in the routing table. BGP


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


38. What effect does (S -G) and (* -G) entries have on router CPU?
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
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
Loopback more resilient than physical interfaces. 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 />


39. What is the layer 2 multicast address and how is it formed? What potential problem is there with this?
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 />
Links = n(n-1)/2 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<br
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


40. What is the command to enable BPG authentication?
R1(config-router)#neighbor 192.168.1.1 password MyPassword<br /><br />OR<br /><br />R1(config-router)#neighbor MyPeerGroup password MyPassword<br /> BGP
Default-Network<br />Static route<br /> BGP
Globally:<br />Router(config)# ip multicast-routing<br />Per Interface:<br />Router(config-if)# ip pim dense-mode<br />Enabling PIM on an interface also enables IGMP operation on that interface.<br /> Multicast
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


41. What is a BGP peer group?

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42. 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?
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
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 /><br />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)'<br /><br />This insures a loop-free environment. If BGP receives a
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


43. What is a BGP route reflector - What is it purpose?
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
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
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
AS-Path<br />Next Hop<br />Origin BGP


44. Name what an update message may include.
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
Group of BGP routers being configured that have the same update policy.<br />Similar to a 'template'; members then assigned to the peer group.<br /> BGP
* = Best route<br />&gt; = Route has been inserted into the routing table<br /> 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


45. Explain the path selection process for BGP? What is the order and what preference does it take?
WM<br />One of three values: <br />IGP - Route is interior to the originating AS. (BGP table shows 'i')<br />EGP - Route learned via EGP. (BGP table shows 'e')<br />Incomplete - Routes origin is unknown - usually when redistributed. (BGP table shows
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)<
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
The BGP Table<br /><br />Command = show ip bgp BGP


46. What is a neighbor call in BGP?
BGP peer 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
Places it in the routing table. BGP
Using a Distribute List to filter outbound routing updates. BGP


47. Name the Well-known discretionary attributes.
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
Globally:<br />Router(config)# ip multicast-routing<br />Per Interface:<br />Router(config-if)# ip pim dense-mode<br />Enabling PIM on an interface also enables IGMP operation on that interface.<br /> Multicast
Local preference<br />Atomic Aggregate 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


48. State 3 functions SDR performs?
Path Vector - policy based routing protocol.<br />Uses BGP attributes are the 'metric'. <br />Path it decides it based on 'hops' where hop is Autonomous Systems.<br /> BGP
Loopback more resilient than physical interfaces. BGP
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


49. What does the 'maximum-paths router' command facilitate?
EBGP = 20<br />iBGP = 200<br /> BGP
Path Vector - policy based routing protocol.<br />Uses BGP attributes are the 'metric'. <br />Path it decides it based on 'hops' where hop is Autonomous Systems.<br /> BGP
Efficiency<br />Performance<br />Scalability with applications<br /> Multicast
Works if router has multiple parallel paths to a destination.<br />ONLY affect number of routes in IP routing table not the route selected at best in the BGP table.<br />Will load balance across equal cost paths in EGP session.<br /> BGP


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

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