{"id":692,"date":"2018-10-26T22:26:59","date_gmt":"2018-10-26T22:26:59","guid":{"rendered":"http:\/\/feralpacket.org\/?p=692"},"modified":"2018-10-26T22:26:59","modified_gmt":"2018-10-26T22:26:59","slug":"multicast-notes","status":"publish","type":"post","link":"https:\/\/feralpacket.org\/?p=692","title":{"rendered":"Multicast Notes"},"content":{"rendered":"

Multicast<\/span><\/p>\n

\n– One-to-many<\/p>\n

\n– Layer 3 address range<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> Class D<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.0<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 239.255.255.255<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> First four bits are always<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -> 1110.<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> Last 23 bits are used to create the MAC address<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 5 bits in the middle can change<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 2^5 = 32 IP address for one MAC address<\/p>\n

\n– Reserved management range<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.x.x.x<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.x<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -> Link-local multicast<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.1 – all nodes on segment<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.2 – all routers on segment<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.3 – Distance Vector Multicast Routing Protocol (DVMRP)<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.5 – OSPF routers<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.6 – OSPF DR routers<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.9 – RIPv2<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.10 – EIGRP<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.13 – PIMv2 (Protocol Independent Multidast)<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.0.18 – VRRP<\/p>\n

\n– 224.0.1.x<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> global multicast<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.1.39 – Auto-RP accouncer<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 224.0.1.40 – Auto-RP Discovery<\/p>\n

\n– 232.x.x.x<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> Source Specific Multicast (SSM)<\/p>\n

\n– 239.x.x.x<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> Administratively scoped addresses<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> Similar to private IP addresses<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> Traffic should not be sent to the Internet\n<\/p>\n

\nMulticast MAC Address<\/span><\/p>\n

\n– xx.xx.xx.xx.xx.xx<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> xx.xx.xx. – Organizationally Unique Identifier (OUI)<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> OUI of multicast MAC addresses is always<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -> 01.00.5E.\n<\/p>\n

\nIf destination IP address is 225.1.1.1<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> First 24 bits<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -> 01.00.5E<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 25th bit is always 0<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> Last 23 bits taken from the multicast IP address<\/p>\n

\n\u00a0\u00a0\u00a0\u00a0 -> 01.00.5E.01.01.01\n<\/p>\n

<\/p>\n

Internet Group Management Protcol (IGMP)<\/span><\/p>\n

\u00a0– A communication protocol between multicast receivers and the last hop routers<\/p>\n

\u00a0– Used to request the traffic sent to a specific multicast address<\/p>\n

Communication between the first hop router and the last hop router is done with multicast routing protocols<\/p>\n

\u00a0– DVMRP<\/p>\n

\u00a0– Core Based Tree (CBT)<\/p>\n

\u00a0– MOSPF<\/p>\n

\u00a0– PIM<\/p>\n

\u00a0 \u00a0 \u00a0-> Dense<\/p>\n

\u00a0 \u00a0 \u00a0-> Sparse<\/p>\n

IGMP Versions<\/p>\n

\u00a0– Version 1 – Old<\/p>\n

\u00a0– Version 2 – Default<\/p>\n

\u00a0– Version 3 – Used for advanced features such as SSM<\/p>\n

Joining the group<\/span><\/p>\n

1. The last hop router sends a periodic IGMP general query every 60 seconds to 224.0.0.1 (all nodes)<\/p>\n

<\/p>\n

2. If there are multiple routers on the same segment, there will be a querier election by comparing the segment facing IP addresses of the router<\/p>\n

\u00a0 \u00a0 \u00a0-> Lower is better<\/p>\n

3. If the querier misses sending 2 consecutive general queries, the other router preempts the querier role<\/p>\n

4. Whenever a client is interested in a specific multicast stream, it sends an IGMP Membership Report message destined to the multicast address it wishes to join<\/p>\n

5. If multiple receivers are present on the same segment, then every receiver hols it’s membership report for a randomly generated time<\/p>\n

6. Other receivers, upon hearing (receiving) the report will suppress their own report<\/p>\n

7. The randomly generated numbs has to be in the range of 1 to the Maximum Response Time (MRT)<\/p>\n

\u00a0 \u00a0 \u00a0-> Default MRT is 10 seconds<\/p>\n

Leaving the group<\/span><\/p>\n

1. Whenever a client wants to leave the group, it sends a “leave-group” message to 224.0.0.2 (all routers)<\/p>\n

2. Upon receiving the “leave-group” message, the router responds by sending a “group-specific-query” to the multicast group address<\/p>\n

3. The query is sent every second for the next 3 second<\/p>\n

\u00a0 \u00a0 \u00a0 -> If nobody replies, the router stops sending multicast traffic out that port<\/p>\n

Configuration on the Last Hop Router (LHR)<\/p>\n

R8(config)# int fa0\/0<\/span><\/p>\n

\u00a0ip igmp query-interval <sec><\/span><\/p>\n

\u00a0ip igmp querier-timeout <sec><\/span><\/p>\n

\u00a0ip igmp query-max-response-time <sec><\/span><\/p>\n

\u00a0ip igmp version { 1 | 2 | 3 }<\/span><\/p>\n

\u00a0ip igmp last-member-query-interval <msec><\/span><\/p>\n

\u00a0ip igmp limit <number of reports><\/span><\/p>\n

\u00a0ip igmp access-group <acl><\/span><\/p>\n

\u00a0ip igmp join-group <ip add><\/span><\/p>\n

Default IGMP Timers<\/span><\/p>\n

\u00a0– query-interval<\/p>\n

\u00a0 \u00a0 \u00a0-> 60 seconds<\/p>\n

\u00a0– querier-timeout<\/p>\n

\u00a0 \u00a0 \u00a0-> 120 seconds<\/p>\n

\u00a0– query-max-response-time<\/p>\n

\u00a0 \u00a0 \u00a0-> 10 seconds<\/p>\n

\u00a0– last-member-query-interval<\/p>\n

\u00a0 \u00a0 \u00a0-> 1000 ms<\/p>\n

ip \u00a0igmp access-group <acl><\/span><\/p>\n

\u00a0– Defines the multicast groups permitted | denied<\/p>\n

ip igmp join-group <ip add><\/span><\/p>\n

\u00a0– Makes the router a receiver<\/p>\n

\u00a0– Good for testing multicast<\/p>\n

\u00a0– Recommended to use a loopback interface<\/p>\n

Multicast Routing Protocols<\/span><\/p>\n

\u00a0– Multicast Tree<\/p>\n

\u00a0 \u00a0 \u00a0-> FLow of multicast traffic from source to receiver for a group<\/p>\n

\u00a0 \u00a0 \u00a0-> On any router which is part of the tree will have an (s,g) entry<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> s – source<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> g – multicast group<\/p>\n

The methods to propogate the traffic from First Hop Router (FHR) to Last Hop Router (LHR)<\/p>\n

\u00a01. Flood and pruse<\/p>\n

\u00a0 \u00a0 \u00a0-> PIM dense mode<\/p>\n

\u00a02. Request to unprune<\/p>\n

PIM Dense Mode<\/span><\/p>\n

\u00a0– Traffic is flooded to every branch to every router<\/p>\n

\u00a0– Every receiving router checks two things<\/p>\n

\u00a0 \u00a0 \u00a0-> Are there any receivers<\/p>\n

\u00a0 \u00a0 \u00a0-> Are there any downstream routers<\/p>\n

\u00a0– By default, PIMv2 is used<\/p>\n

\u00a0 \u00a0 \u00a0-> uses 224.0.0.13 to form neighbors and send periodic hellos<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Hellos sent every 30 seconds<\/p>\n

\u00a0– Messages<\/p>\n

\u00a0 \u00a0 \u00a0-> Prune<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Request to stop sending traffic<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Upon receiving this message, the router stops sending traffic for 3 minutes<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> After the 3 minutes, multicast traffic is sent again<\/p>\n

\u00a0 \u00a0 \u00a0-> Graft<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Unprune a pruned link<\/p>\n

\u00a0 \u00a0 \u00a0-> Graft Acknowledgement<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Upstream router acknowledges receiving a Graft message, but it may not have traffic to send<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Upstream router may have to send it’s own Graft message<\/p>\n

\u00a0 \u00a0 \u00a0-> Static Refresh<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> This message is sent from the receiving router to upstream router to refresh the prune time<\/p>\n

Configuration of PIM Dense Mode<\/p>\n

R1(config)# int fa0\/0<\/span><\/p>\n

\u00a0ip pim dense-mode<\/span><\/p>\n

sh ip pim neighbors<\/span><\/p>\n

sh ip pim interface<\/span><\/p>\n

sh ip mroute<\/span><\/p>\n

\u00a0– Shows your location in the multicast tree<\/p>\n

\u00a0– Shows the number of active multicast trees (flows) along with detailed information<\/p>\n

\u00a0 \u00a0 \u00a0-> Source of the multicast<\/p>\n

\u00a0 \u00a0 \u00a0-> Multicast group<\/p>\n

\u00a0 \u00a0 \u00a0-> Incoming interface<\/p>\n

\u00a0 \u00a0 \u00a0-> Outgoing interface and their states<\/p>\n

\u00a0 \u00a0 \u00a0-> Flags<\/p>\n

Flags<\/p>\n

\u00a0– D<\/p>\n

\u00a0 \u00a0 \u00a0-> Dense mode<\/p>\n

\u00a0– S<\/p>\n

\u00a0 \u00a0 \u00a0-> Sparse mode<\/p>\n

\u00a0– P<\/p>\n

\u00a0 \u00a0 \u00a0-> Pruned<\/p>\n

\u00a0– T<\/p>\n

\u00a0 \u00a0 \u00a0-> Shortest Path Tree<\/p>\n

sh ip mroute<\/span><\/p>\n

\u00a0(10.0.0.1, 255.1.1.1) \u00a0 \u00a0 \u00a0 \u00a0 \u00a0uptime \/ expire<\/p>\n

\u00a0 \u00a0 \u00a0incoming interface: fa0\/0<\/p>\n

\u00a0 \u00a0 \u00a0outgoing interface:<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0s0\/0 -> uptime \/ expire<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0s0\/1 -> uptime \/ expire<\/p>\n

Reverse Path Forwarding (RPF)<\/span><\/p>\n

\u00a0 \u00a0 \u00a0-> Any router accepts the multicast on an interface only if that interface is used to back to the source network<\/p>\n

<\/p>\n

By default, the unicast routing table is checked for RPF check<\/p>\n

\u00a0– It can be overridden by using static mroutes<\/p>\n

ip mroute <source ip> <source mask> <incoming int><\/span><\/p>\n

ip mroute 10.0.0.0 255.0.0.0 s0\/0<\/span><\/p>\n

Troubleshooting section of the lab usually has RPF failures<\/p>\n

Rendezvous\u00a0Point (RP)<\/span><\/p>\n

<\/p>\n

Request to unprune (sparse mode)<\/p>\n

\u00a0– All ports are pruned by default<\/p>\n

\u00a0– Ports are unpruned on request<\/p>\n

\u00a0 \u00a0 \u00a0-> Join message<\/p>\n

\u00a0– (*,g) join message is sent by the LHR to RP<\/p>\n

\u00a0 \u00a0 \u00a0-> Creates a Shared Tree<\/p>\n

(s,g) -> Shortest Path Tree (SPT)<\/p>\n

(*,g) -> Shared Tree<\/p>\n

FHR sends a unicast message to RP call a Register message<\/p>\n

\u00a0– The message is a request to RP to send the join message<\/p>\n

\u00a0– Sent every 60 seconds<\/p>\n

\u00a0– Join messages are sent every 60 seconds<\/p>\n

\u00a0– Upon receiving a Register message, the RP sends an (s,g) join message towards the source<\/p>\n

\u00a0– After receiving traffic on RP, the RP sends a Register-stop message to FHR<\/p>\n

<\/p>\n

SPT-Switchover<\/span><\/p>\n

\u00a0– Once the LHR joins the shared tree and receives the first packet, it knows about the source and sends a (s,g) join message towards the source<\/p>\n

\u00a0– When traffic starts coming through the SPT, the router sends a prune message to the shared tree<\/p>\n

Configuring PIM Sparse Mode<\/p>\n

\u00a01. Activate multicast routing<\/p>\n

\u00a02. Configure interfaces for PIM sparse mode<\/p>\n

\u00a03. Configure RP information<\/p>\n

\u00a0 \u00a0 \u00a0-> Manual<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Configure RP on all routers manually\u00a0<\/p>\n

\u00a0 \u00a0 \u00a0-> Automatic<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Distribute RP\u00a0information\u00a0by using a protocol (dynamic)<\/p>\n

On all routers<\/p>\n

R1(config)# ip multicast-routing<\/span><\/p>\n

\u00a0ip pim rp-address <ip add> [<acl>]<\/span><\/p>\n

int s0\/0<\/span><\/p>\n

\u00a0ip pim sparse-mode<\/span><\/p>\n

The IP address of the RP must be reachable<\/p>\n

\u00a0– If a loopback interface is used as the RP, PIM must be activated on the interface<\/p>\n

ACL<\/p>\n

\u00a0– specifies the group the RP will service<\/p>\n

\u00a0– By default, the RP will service any multicast IP address<\/p>\n

\u00a0 \u00a0 \u00a0-> 224.0.0.0 – 239.255.255.255<\/p>\n

<\/p>\n

R1(config)# ip multicast-routing<\/span><\/p>\n

\u00a0int fa0\/0<\/span><\/p>\n

\u00a0 ip pim sparse-mode<\/span><\/p>\n

\u00a0ip pim rp-address 2.2.2.2<\/span><\/p>\n

R2(config)# ip multicast-routing<\/span><\/p>\n

int range lo0, fa0\/0 – 1<\/span><\/p>\n

\u00a0 ip pim sparse-mode<\/span><\/p>\n

ip pim rp-address 2.2.2.2<\/span><\/p>\n

R3(config)# ip multicast-routing<\/span><\/p>\n

ip pim rp-address 2.2.2.2<\/span><\/p>\n

int fa0\/0<\/span><\/p>\n

\u00a0ip pim sparse-mode<\/span><\/p>\n

int lo0<\/span><\/p>\n

\u00a0ip pim sparse-mode<\/span><\/p>\n

\u00a0ip igmp join-group 225.1.1.1<\/span><\/p>\n

Designated Router (DR)<\/span><\/p>\n

\u00a0– Used on multiaccess network<\/p>\n

\u00a0– On receiving side if there are multiple routers, one will be elected the DR<\/p>\n

\u00a0– Only the DR will send join messages<\/p>\n

<\/p>\n

On sending side if there are multiple routers connected to the same segment, one will be elected as the DR<\/p>\n

\u00a0– The DR will send the Register message to the RP<\/p>\n

DR Election<\/p>\n

\u00a0– higher is better<\/p>\n

\u00a0– Checks priority<\/p>\n

\u00a0 \u00a0 \u00a0-> Default is 1<\/p>\n

\u00a0– Then checks IP address of the segment-facing interface<\/p>\n

int fa0\/0<\/span><\/p>\n

\u00a0ip pim dr-priority 100<\/span><\/p>\n

Filter Join Messages<\/span><\/p>\n

\u00a0– Only for (*,g) join messages<\/p>\n

\u00a0–\u00a0Can be configured anywhere, but it is best to configure on the RP itself<\/p>\n

ip pim accept-rp <ip add of RP> [<acl>]<\/span><\/p>\n

<\/p>\n

R2(config)# access-list 1 permit 225.1.1.1<\/span><\/p>\n

ip pim access-rp 1.1.1.1 1<\/span><\/p>\n

\u00a0(*,225.1.1.1<\/p>\n

\u00a0 \u00a0 \u00a0RP -> 1.1.1.1<\/p>\n

Filter Register Messages<\/span><\/p>\n

\u00a0– Only configured on the RP<\/p>\n

\u00a0– This does not work if the source is also the DR<\/p>\n

ip pim accept-register { list <acl> | route-map <name> }<\/span><\/p>\n

ACL -> extended<\/p>\n

\u00a0– What source\u00a0register\u00a0message is coming from<\/p>\n

\u00a0– What group it is requesting<\/p>\n

Troubleshooting Multicast<\/span><\/p>\n

ping 225.1.1.1<\/span><\/p>\n

\u00a0– By default, the source is all interfaces where PIM is activated<\/p>\n

\u00a0 \u00a0 \u00a0-> If there are 3 interfaces, 3 pings will be sent<\/p>\n

\u00a0– To ping from a specific source, use extended ping<\/p>\n

\u00a0– It helps if ip igmp join-group 225.1.1.1<\/span> is configured on a LHR<\/p>\n

\u00a0– To troubleshoot multicast, use an extended ping and set the repeat count to a large number<\/p>\n

\u00a0 \u00a0 \u00a0-> Multicast is hard to troubleshoot if there is no multicast traffic<\/p>\n

\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 -> Troubleshooting QoS is worse in a lab environment<\/p>\n","protected":false},"excerpt":{"rendered":"

Multicast<\/p>\n","protected":false},"author":1,"featured_media":684,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[46,31],"class_list":["post-692","post","type-post","status-publish","format-standard","hentry","category-ccie","tag-multicast","tag-published"],"_links":{"self":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/692","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=692"}],"version-history":[{"count":1,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/692\/revisions"}],"predecessor-version":[{"id":700,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/692\/revisions\/700"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/media\/684"}],"wp:attachment":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=692"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=692"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=692"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}