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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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1. What are three different common ways to perform BGP multihoming with regard to routing table?
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
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
The is the multicast bit. Multicast
WM Next hop address is entry point into the next AS along the path to that destination network. It does a recursive lookup to the routing table which should have learned the route from its IGP. in IBGP the next hop advertised by EBGP should

2. Explain the MED attribute.

3. 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?
The neighbor expects to see the updates from the source address configured in the neighbor statement. BGP
This should only be for ISP's An improperly configured AS (that is not meant to be a transit) could inadvertently become one. BGP
Loopback more resilient than physical interfaces. 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

4. How does a host learn about available multicast streams?
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
Well know predefined group Directory - sd / SDP Webpage/URL Email link Multicast
Rule: Router must be known by an IGP before it may be advertised by BGP peers. Prevents 'blackholes' when AS is a transit network and not all speaker are running BGP Should be left on it AS is a transit AS and not all routers run BGP. 
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 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. 
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
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
Rule: Router must be known by an IGP before it may be advertised by BGP peers. Prevents 'blackholes' when AS is a transit network and not all speaker are running BGP Should be left on it AS is a transit AS and not all routers run BGP. 

6. Name 4 verification commands for BGP and what they display?
The is the multicast bit. Multicast
Cluster - combination of RR and its clients. Can have multiple clusters in an AS. Originator ID - carries router ID of the route's originator Cluster ID - configured when multiple RR in a cluster. Cluster list - sequence of cluster ID
BGP Table - BGP topology database - information BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. 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

7. 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/
Default-Network Static route BGP
Links = n(n-1)/2 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

8. What does PIM use for its multicast routing calculations?
Bidirection PIM mode - designed for many to many applications. Source Specific Multicast (SSM) ; builds only source specific shortest path trees. Multicast
MOSPF DVMRP CBT PIM Dense Mode PIM Sparse Mode PIM Sparse-Dense Mode Multicast
<img src='9618cf01b9422f541fc213b74a3bd9de.png' /> Multicast
The unicast routing table. No routing updates are sent between PIM routers. Multicast

9. IOS command to configure router to be a member of an IGMP group or statically connected member.
Member of a group: Router#(config) ip igmp join-group group-address Statically connected: Router#(config) ip igmp join-group group-address In this mode router forwards (fast switches) group packets but itself does not accept group
Local preference Atomic Aggregate BGP
* = Best route > = Route has been inserted into the routing table BGP
This router originated the route. BGP

10. What is a neighbor call in BGP?
Local preference Atomic Aggregate BGP
BGP peer 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
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

11. Explain the IGMPv3 membership process and new features.
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
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/
RFC 1112 Sends membership query every 60 - 120 seconds to 224.0.0.1 Hosts send membership report in response to the query Multicast
Default-Network Static route BGP

12. What is the terminology for BGP route reflector?

13. What is the difference between iBGP and eBGP?
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
This router originated the route. BGP
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast

14. What is the IOS command to check for IGMP group members? What info does it reveal?
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
Must insure loopback is reachable in the routing table. 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. 
Router#show ip igmp group Group address - interface - uptime - expires - and last reporter. Multicast

15. What is the command to configure a BGP RR? 
Places it in the routing table. 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
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. 

16. What are some of the obstacles with IGMP and multicast in general as it relates to layer 2/switches?
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
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
Reverse Path Forwarding is the forwarding logic multicast of multicast. It is the opposite of unicast in that is forwards AWAY from source as opposed to towards the receiver. Multicast
IGMP Snooping - requires special ASICS can degrade performance with it; is supported by multiple vendors. CGMP - Cisco proprietary - only work on Cisco hardware; resource friendly GMRP - Replaced by MRP; obscure Manually - Performance

17. What is the IBGP Split Horizon rule? What does this accomplish?
Loopback more resilient than physical interfaces. BGP
Members leave through attrition; no leave group message. This keep traffic flowing for a period of time even with no group members. Multicast
Default-Network Static route BGP
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP

18. Explain the Local Preference attribute. 

19. What are the commands to enable multicast routing on a router?
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
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
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
It actually determines which networks are advertised. BGP

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

21. 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
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
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

22. 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
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
Default-Network Static route BGP
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
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

23. What is the full mesh versus partial mesh IBGP and What are the implications of each?
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
Session description & announcement. Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast
Router#show ip igmp group Group address - interface - uptime - expires - and last reporter. Multicast
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

24. What is the layer 2 multicast address and how is it formed? What potential problem is there with this?
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 BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. BGP
Open - Version - AS - Hold Time - BGP Router ID - Optional Parameters Keepalive - Sent every 60 seconds by default; hold time 180 Seconds. Update - Information on only ONE path; Notification - When error condition detected BGP

25. Explain the AS-Path attribute.

26. What is a BGP black hole and how is it avoided?
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
This router originated the route. BGP
WM List of AS numbers pre-pended with a list of AS numbers that the route has traversed and the originating AS at the end. 'Path to 192.168.1.0 is (65500 - 65420 - 65874)' This insures a loop-free environment. If BGP receives a
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

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

28. Explain what role IGMP plays.
OT Allows the router to 'tag' and thus implement policy based on this tag. BGP
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
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
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

29. What does a '*' and '>' mean in the BGP table?
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 -
* = Best route > = Route has been inserted into the routing table BGP
R1(config-router)#neighbor MyPeers peer-group R1(config-router)#neighbor 10.1.1.1 remote-as 64513 R1(config-router)#neighbor 10.1.1.1 peer-group MyPeers BGP
Loopback more resilient than physical interfaces. BGP

30. What is the key difference between how a multicast routing protocol forwards packets versus a unicast routing protocol?
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
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
BGP peer BGP
Cluster - combination of RR and its clients. Can have multiple clusters in an AS. Originator ID - carries router ID of the route's originator Cluster ID - configured when multiple RR in a cluster. Cluster list - sequence of cluster ID

31. What effect does (S -G) and (* -G) entries have on router CPU?
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
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
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

32. Name what an update message may include.
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
'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
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
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast

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

34. Explain the Origin attribute.

35. What are two methods of establishing a gateway of last resort?
* = Best route > = Route has been inserted into the routing table 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 Transport session announcement via 224.2.127.254. Creation of new sessions. Multicast
Default-Network Static route BGP

36. What are the basic commands to enable BGP - define a BGP peer relationship and advertise a network?
Router#(config) router bgp 1 Router#(config-router) neighbor 192.168.1.1 remote-as 1 Router#(config-router) network 192.168.0. mask 255.255.255.0 BGP
Must insure loopback is reachable in the routing table. BGP
Routes learned through IBPG are never propogated to other IBGP speakers. This is a loop prevention mechanism. BGP
The unicast routing table. No routing updates are sent between PIM routers. Multicast

37. What is a BGP peer group?

38. What is the significance of the 8th bit in the MAC address?
EBGP is an adjacency between BGP peers in different AS; iBGP peers are in same AS. BGP
The is the multicast bit. Multicast
* = Best route > = Route has been inserted into the routing table BGP
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

39. What are the 4 BGP packet types? What do they contain?
Router(config-router)# neighbor 192.168.1.1 remote-as 65000 Router(config-router)# neighbor 192.168.1.1 route-reflector-client BGP
Open - Version - AS - Hold Time - BGP Router ID - Optional Parameters Keepalive - Sent every 60 seconds by default; hold time 180 Seconds. Update - Information on only ONE path; Notification - When error condition detected BGP
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
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast

40. What are the commands to configure a BGP peer group?
R1(config-router)#neighbor MyPeers peer-group R1(config-router)#neighbor 10.1.1.1 remote-as 64513 R1(config-router)#neighbor 10.1.1.1 peer-group MyPeers BGP
Links = n(n-1)/2 BGP
Local preference Atomic Aggregate BGP
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list Multicast

41. What advantage is there it establishing a neighbor relationship using a loopback interface?
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
Loopback more resilient than physical interfaces. BGP
BGP Table - BGP topology database - information BGP Neighbor Table - list of connected neighbors IP Routing Table - Duh. BGP
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast

42. Name the Well-known discretionary attributes.
Local preference Atomic Aggregate BGP
EBGP = 20 iBGP = 200 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
Router#(config) ip pim spt-threshold {rate | infinity} [group-list access-list] Multicast

43. What is one mechanism that GURANTEES the BGP AS path is loop free?
Router#(config) ip pim send-rp-announce interface_type scope ttl group-list access-list 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
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
The router will not accept a routing update that includes its AS number in the path. BGP

44. How is the BGP network command differ from IGP's?
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
It actually determines which networks are advertised. 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
Router#show ip igmp group Group address - interface - uptime - expires - and last reporter. Multicast

45. How does RPF avoid routing loops?
Must insure loopback is reachable in the routing table. 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
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. 
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' 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/
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
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
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. What does BGP use for communication? What advantage does it offer?
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
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
EBGP = 20 iBGP = 200 BGP
TCP port 179 Reliability; uses sliding window Triggered - incremental updates made very efficient BGP

48. Explain the AS format and ranges?
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
16 bit number 1 to 65535 1-64511: Public AS 64512-6535: Reserved for private AS BGP
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
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 -

49. Describe how PIM-DM operates.

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