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93 Cards in this Set

  • Front
  • Back
Describe multicast.
1. One packet is replicated by network to subset of hosts. Multicast Routing Protocols build tree between source and hosts. And routers replicate packets out of those interfaces.

2. Server sends to multicast destination. Doesn't care who. One destination is the equivalent to one IPTV Channel.

Multicast Addresses
1. 224.0.0.0/4 (224.0.0.0 - 239.255.255.255) 110

2. Permanent Address 224.0.0.0/8


- 224.0.0.0/24 Link Local/Unroutable


- 224.0.1.0/24 Routable


3. SSM 232.0.0.0/8


4. 233.0.0.0/8 GLOP Adress


- BGP ASN is next two bytes giving every as 256 globally unique multicast addresses ASN 1 is 00000000 00000001. So it would be 233.0.1.0/24


4. Admin Scope (Private) 239.0.0.0/8

Control Plane Protocols and Functions?
IGMP used by hosts to notify router of groups it wants to join. PIM is used between routers to signal what groups it wants to join and leave. Used to build tree between sender and receivers.
Data Plane Components
RPF is reverse path forwarding. Multicast uses RPF to verify loop free topology (which has already been determined by IGP). It will make sure the source address of the packet is where the router would route to. Multicast Forwarding Table lists all of the interface where the packet should be replicated.
How many IGMP versions and which is default?
IGMP v1, v2, and v3. V2 is the default.
How to enable IGMP on router interface?
Enabling PIM will enable IGMP.
IGMPv1 messages and *,G or S,G?
Host Membership Query - Query used by router to see if members of group still exist.



Host Membership Report - Report used by client to report groups that it wants to join.




*,G from host.

With IGMPv1 who determines who sends queries if there are multiple routers on the segment?
The PIM DR determines who responsible. With DR it is the DR priority and then highest IP.ip pim dr-priorityBehavior changes with IGMPv2
IGMPv2 messages, *,G or S,G, and what function was added?

IGMPv1 Host Membership Query and Host Membership Report.




Explicit leaves - host can now report a leave of a particular group




Group specific queries - follow explicit leaves to see if anyone is remaining.




*,G joins from host.




Querier Election based on lowest IP (no longer PIM DR which is highest and sends register/prune toward RP).

IGMPv3 messages and *,G or S,G?
Same as IGMPv2 -

Group specific queries. Explicit leaves. Addition is S,G joins.

What are the following commands? What is the default query interval and timeout?

ip igmp query-interval 60


ip igmp querier-timeout seconds

How often the v1/v2/v3 IGMP router should query. 60 seconds is default.



How long v2/v3 routers should wait before not hearing anything and start another re-election. Default is x2 query interval. There is no election with v1.

What does this command do?

ip igmp query-max-response-time seconds

How long a host has to respond before router deletes group. Each host will pick a random value under the max and respond. Hope is one host responds and all others suppress report conserving resources. IGMPv1 is 10 seconds by default but doesn't delete the group. It must wait x3 the query interval.
What do these commands do? What are the defaults?

ip igmp last-member-query-count

ip igmp last-member-query-interval
How many queries to send after explicit leave is heard and how often to send after a explicit leave report is signaled.



Count default is 2.


Query interval is 1.

What does this command do?

ip igmp immediate-leave




ip igmp explicit tracking

Tell router to not query if a leave is received and just delete the group.



Track each ssm receiver and not just the S,G

What is the purpose of IGMP snooping? Is it on by default?
IGMP snooping allows a l2 switch to learn of Mrouters and mutlciast recievers. It is on by default.
How does IGMP snooping work?
It listens for IGMP query messages to determine where mrouter is.



It intercepts IGMP report messages which also breaks the report suppresion. It will generate reports to the mrouter interface. Once it hears a report from a host they are added to the VLAN group entry table in CAM.




It will also listen to leave messages and send a query down port to make sure no other devices are present and generate leave messages to router.

Does IGMP snooping restrict multicast for routing protocols?




Does TCN impact snooping table? Can it be changed?

No, there are no query or reporting mechanisms.




Yes, a TCN will cause multicast to flooded to every port for the query interval. Can be disabled with configuration.


no ip igmp snooping tcn flood




Or tuned down the query interval


ip igmp snooping tcn flood query count

What does this command do?

Igmp snooping


no ip igmp snooping vlan 20

Enable IGMP snoopingDisable IGMP snooping for a VLAN.
What does this command do?

ip igmp snooping last-member-qeuery-interval 500


Ip igmp snooping vlan 22 immediate-leave

How long to wait to consider this last member.



Configures immediate leave for the VLAN. It will generate leave report if it gets one leave report.

What do these commands do?


ip igmp snooping vlan 1 mrouter interface gigabitethernet 1/0/2




ip igmp snooping vlan 1 static 200.000.000.000 interface gigabitEthernet1/0/1

Configures a static mrouter interface on IGMP snooping switch. Normally a switch would listen to query messages.




Configures static hos entry on IGMP snooping switch. Normally a switch would list to host reports.




Static overrides manual.

What does this command do? Where else can it be applied?



interface FastEthernet0/3


switchport access vlan 50


switchport mode access


ip igmp filter 1


!


Ip igmp profile1


permit


range 229.13.13.13

Command is only available on IGMP snooping switch. And IGMP snooping must be enabled. It is used to limit what IGMP groups are joined at the switch level.



Can be applied to port, SVI, or per port per VLAN.





What is IGMP proxy? What is the command?
It allows one router to send IGMP joins to another router for the purpose of turning into a PIM join.

inter f0/0 --upstream interface


ip igmp helper-address

What is MLD?
Multicast Listener Discover Protocol and it replaces IGMP in IPv6.
What is MLDv1 and MLDv2 equal to in IGMP?
MLDv1 = IGMPv2 and MLDv2=IGMPv3
What are the messages?
Query, Report, Done (which is like leave)
How to enable MLD?
Enabling IPv6 multicast routing enable PIM and MLD.

What is the default MLD query interval?


What is the default IGMP query interval?


What is the default MLD query timeout?
What is the default IGMP query timeout?


What is the default MLD max response time?


What is the default IGMP max response time?


What is the default MLD last member query interval?


What is the default IGMP last member query interval?

MLD - 125s IGMP 60


MLD - x2 255s IGMP 120


MLD - 10 IGMP 10


MLD - 1 IGMP 1

Explain PIM snooping.
It is for a large l2 switched network with several PIm neighbors on the edge. It allows switches to limit to only interested ports.



ip pim snooping

What other snooping mechanism must be enabled for PIM snooping to work?

IGMP Snooping

Which snooping mechanisms are on by default - IGMP, PIM, and MLD?

IGMP yes, PIM no, and MLD yes

What are the PIM versions? Which is enabled by default? What is purpose of PIM
PIM v1 and PIM v2. PIM v2 enabled by default.PIM is used for router to router communication. It send PIM join and prune messages and build multicast tree.
Which router is responsible for send register or PIM joins.
The router with the highest DR priority or highest IP address if DR is the same.
What are the PIM modes? How are neighbor established?
Sparse-Mode - pull technology explicit joinDense-Mode - implicit join push technolgySparse-Dense - leverage dense of no RP is configured.


(config-if)ip pim [sparse-mode | dense-mode | sparse-dense ]




make sure neighbors are on both sides. It is not acknowledged like OSPF. One side can see one side and not the other side.

What are the PIM message types
0 Hello

1 Register - sent by DR on LAN toward RP to inform of S,G


2 Register-Stop - sent by RP when it doesn’t want the message


3 Join/Prune - add or remove interfaces from OIL


4 Bootstrap (version 2)


5 Assert


6 Graft


7 Graft Ack


8 Candidate-RP-Advertisement (version 2)


9 State Refresh

What are the type of trees?
RPT or Shared TreeShortest Path Tree or Source Based Tree (SPT)
What is the first step for PIM Dense Mode?
Discover all neighbors using 224.0.0.13.
With PIM Dense Mode once neigbots are up what happens when a server sends traffic?
The first router sends to all PIM interface creating a S,G with those interfacs in the OIL.
What two things causes neighbors to send Prune messages?
If the mcast data comes on an interface that fails RPF it sends a prune message. If there are no recievers it sends a prune message.
What happens at State Refresh in PIM?
The routers resend data down pruned links. The neighbors after to request to have the data pruned again.
What is purpose of Graft and Assert Message?
Graft message is so router doesn't have to wait to be rejoined for staterefresh to be joined to tree. Neighbot will send Graft Ack. Assert message is used when multi routers on segment are trying to send mcast data. Both will send assert message. (1) lowest AD (2) lowest metric (3) highest IP will determine winner.
What are the PIM-SM operation steps.
1. Discover neighbors and elect DR to talk to RP.

2. RP - static, autorp, bsr


3. Tell RP about sources - register messages sent by DR (highest priority and then IP)


4. Tell RP about receivers by joining the RPT - send *,G join ip RPF tree toward RP. The router will add to OIL if the packet passes RPF.


5. Build shared tree from sender to recievers through RP.


6. Last hop router joins SPT if spt threshold is configured.


7. Leave shared tree or RPT


8. Maintenence

What is purpose of PIM DR with PIM-SM and how is it decided?
PIM-DR sends register messages to RP and PIM priority then highest IP address.
What do PIM register messages look like and what happens to the multicast traffic from the server during the buidling of the tree?
PIM register messages and multicast messages are all encapsulated in unicast from the DR to the RP. If RP has interfaces join to *,G it will deencapsulate and send down *,G (shared tree) to recievers. It will also send a register-stop and build an S,G to the source. If no interfaces it will send a register-stop to DR. The DR will try again in one minute if server is still sending.RP will do an RPF on the DR source.
What do routers with recievers do to join the RPT and let the RP know there are interested recievers?
Each router send a *,G PIM join out the RPF interface toward the RP. The recieving router will create *,G and add interface to OIL or add interface to OIl if *,G already exists. It will do RPF to determine where to send PIM join.
what command shows RPF interface for RP
show ip rpf
Once router nearest to source hears the source address of the multcast server what can happen?
The router can now join the shortest path tree (SPT).
what command will instruct last hop router to join SPT and leave RPT?
(config-if)ip pim spt-threshold {kbps| infinity} group-list access-list



the default is zero which means join as soon as packet is received.

What is sparse-dense mode?
Multicast groups are tied to RP. You can limit what group a router is an RP for. Sparse-dense tells router to operate in dense mode if no RP is available for the multicast address.
Where does RP or receivers do RPF check for?
RP performs RPF on source identified PIM register messages from DR and Data Plane Packets from sourceRPF is done before routers sends PIM join up tree toward RP. Receiver routers perform RPF on RP for data on (*,G) and Source for (S,G)
Why do issues occur with RPF and tunnels?
Tunnel are used in cases where SP or transport doesn't support multicast. So tunnel is only there for multicast and you don't want any unicast to go over tunnel.Mroute to RP over tunnel and Mroute for source over tunnel should take care of all the RPF conditions.
Where does the RPF RIB get information from? Three places..How mcast router decide which mroute to use?
1. Unicast RIB but only for routes learned over interfaces that are enabled with PIM

2. Static mroutes


3. Multicast BGPAdmin distance always take precedence over longest match.

When looking in RPF RIB routers search behavior is different from IGP. Explain. Can this be changed?
The router will check the RPF RIB on the source addresses of packets for RPF lookup. It can be learned from multiple sources. Unicast RIB, static mroutes, mcast BGP. The admin distance will take precedence over longest match. Meaning I can have a /24 and /32. If the /24 has higher admin distance I will take that one.
what is the implication of configuring ip mroute 0.0.0.0 0.0.0.0 x
tells router that all source must come through this interface. Remember RPF check says the source must come from the interface in which I route to the source. If not this is a loop. mroute has better admin distance. If I get packets that should come in interface but that doesn't match the mroute I will get a failure.
What is Bi-Dir?
PIM-SM is a unidirectional tree. It is PIM-SM but with the abilitiy with bidirectional trees. It works well when you have devices that are sources and receivers for the same group.
How to enable Bi-Dir?
ip pim bidir-enable globally and add the bidir option to the various RP options.
What is SSM?
Source Specific Multicast is also a variation of PIM-SM but you don't need the RP. It only uses S,G. Must use IGMPv3 for sources to register using the S,G.
What is the default SSM range?
232.0.0.0/8
SSM configuration?
Configure PIM-SM but enable IGMPv3 and configure your SSM range.ip pim ssm defaultorip pim ssm range (ACL) if you want to use another range besides 232.0.0./8
What are the RP methods?
Static, Auto, BSR

What does this command show - show ip pim tunnel?

When an RP is configured a tunnel is made so the unicast register stop and start messages can flow.

What is different about the PIM tunnel on the RP from all others?

The RP has one tunnel for Encapsulation and one for Decapsulation. All others just have tunnel for encapsulation.

What needed to configure static RP?
All routers need to be configured with RP address.

ip pim [vrf vrf-name] rp-address rp-address [access-list] [override] [bidir]

What does the override and access-list keywords provide?
Override says static overrides autoRP or BSR learned RPs. By default dynamic is better than static. The ACL allows for group to RP association.
What does log message "not willing to be RP mean"?
The router has been configured as RP for group on a neighbor but the router is not configured to be RP for that group locally.
What is auto-rp and what are the two components?
Auto-Rp dynamically assign the RPs to PIM-SM network. Components are candidate RPs and Mapping Agents. When configured PIM neighbors forward and accept announce messages and accept joins for the 224.0.1.40 (MA)
What command configures the RP and Mapping Agent?
RP announcing itself

ip pim [vrf vrf-name] send-rp-announce {interface-type interface-number | ip-address} scope ttl-value [group-list access-list] [interval seconds] [bidir]


MA announcing what it has found


ip pim [vrf vrf-name] send-rp-discovery [interface-type interface-number] scope ttl-value [interval seconds]

What interface should be used? What additional configuration is required for just Mapping Agent.
Should use loopback and the interface must be in PIM with the mapping agent.
What address does C-RP and MA use? Why does TTL matter?
C-RP send to 224.0.1.39 and MA send to 224.0.1.40. TTL sets the scope of the messages. It must be configured for peers to here.
What command is needed for PIM neighbors to accept and forward announce messages and accept joins for the 224.0.1.40?
ip pim autorp listener
How is RPF performed on AutoRP control plane messages?
It is performed on the source address of the interface specified in the announce and discovery commands.
What if there are multiple MAs? Multiple RPs?
The highest IP wins for both.
What is BSR?
It is the industry standard which came after auto-rp. Doesn't use separate data plane groups for learning RP and distributing information. Instead the BSR announces itself first (one to do election with other BSRs, the highest priority wins, two to tell candidate RPs where BSR is). The candidate RPs will send unicast message to BSRs letting them know about there presence. The BSR will use same mechanism to advertise RPs send to 224.0.0.13 which is advertise hop-by-hop using split horizon.

What protocol is used to send BSR messages?

PIM 224.0.0.13 with TTL of 1

How to configure rp candiate (bsr)?
ip pim rp-candidate (interface-type interface number) [group-list acl] [interval] [priority]
How to configure candidate bsr (aka mapping agent)?
ip pim bsr-candidate (interface-type interface number) [hash-mask-length] [priority]
What does the multicast boundary in do?
It stops multicast source traffic from coming it. Standard ACL can be used for *,G or Extended can be used for S,G
What does the multicast boundary out do?
It prevents mroute states from being created on an out. PIM Joins or IGMP joins do not lead to interfaces in OIL.
What is MSDP?
multicast source discovery protocol. It allows different RPs to learn about sources that haven't registered to it. This can be configured with redundancy (anycast addres) or no redundancy. With no redundancy the routers share Source Active (SA) messages..

R1


ip msdp peer 1.1.1.1 connect-source lo0


R3


ip msdp peer 3.3.3.3 connect-source lo0




with anycast both routers share same address.R1


ip msdp peer 11.11.11.11 connect-source lo11 int lo1


ip add 1.1.1.1/32


ip pim rp-address 1.1.1.1




R3


ip msdp peer 33.33.33.33 connect-source lo33int lo0


ip add 1.1.1.1/32


ip pim rp-address 1.1.1.1

What is an Source-Active (SA) filter with MSDP?
- SA Filter allows for filtering of source messages between MSDP peers. Can filter in or out.



ip msdp sa-filter in list 111


ip msdp sa-filter out list 111

What protocol replaces IGMP with IPv6? What versions are there and how do they align to IGMP?
Multicast Listener Discovery Protocol (MLD)MLDv1 = IGMPv2 *,G

MLDv2 = IGMPv3 S,G

How to configure router to join mld group?
(config-if)ipv6 mld join-group ff08:106::1
What is the IPv6 multicast address space?
FF00::/8








Multicast starts with FF with X usually 0. What does the Y stand for an what are the possible options? What is the global unicast address?

FFXY where X is usually 0 and Y is scope.1 = node, 2 = link, 5 site, 8 organization, E is global.




Global Multicast is FF0E::/8

What are the common link local and site local addresses?

Link Local - ff02::1 all routers, ff02::5 all ospf,


Site Local - ff05::1:2 all routers, ff05::1:3 all DHCP

What mode does IPv6 support?
Only sparse mode
How to configure it? What different about the interfaces once configured when compared to IPv4?
(config)ipv6 multicast-routing


All interfaces with IPv6 address are enabled with PIM and MLD




(config-if)no ipv6 pim

What are the RP methods with IPv6 PIM? How to show the valid RP
Static, BSR, and embedded.



With IPv4 it is show ip rp mappings. With PIM it is show ip pim range-list

Configure static RP for IPv6 and IPv4
ipv6 pim rp address 2001:103::1

ip pim rp address 1.2.3.4

Configure bsr for IPv6 and IPv4
ipv6 pim bsr candidate rp

ipv6 pim bsr candidate bsr i

How to add ipv6 multicast route
ipv6 route .... multicast

What does the embedded RP address start with?

FF7::/12




The embedded has to do with the FFXY where X says whether or not RP address in embedded inside of multicast address. The Y still shows the scope.





With this embedded address FF7E:0240:2001:2:2:2:1 what is the actual RP address?

2001:2:2:2::2/64

With this embedded address FF7E:0240:2001:2:2:2:1 what does the 02 stand for? The 40? The 2001:2:2:2? The :1?

The interface ID


The prefix length for the RP address 64 bits in hex


The 64 bit prefix


The group ID