Wednesday, 20 November 2019

PIM Sparse Mode


PIM Sparse Mode 



(PIM-SM)  PIM Sparse Mode explicitly builds unidirectional shared trees rooted at a (RP) rendezvous point per group, and optionally creates shortest-path trees per source. (PIM-SM) PIM Sparse Mode generally scales fairly well for wide-area usage.




Sparse-mode protocol do not forward the group traffic to any other router unless it receives a message from that router  requesting copies of packet sent to particular group.

The PIM spares mode operation begins with the packet being forwarded to special router called the rendezvous point (RP).


PIM Sparse Mode uses explicit join means (not receive unless you ask for). PIM Sparse Mode uses both shared tree & source tree, more scalable.

let see the configuration for better understanding.

Topology:


GOAL:


  • configure the topology as per the diagram 
  • configure the IP addresses as per the topology 
  • configure OSPF 100 advertise the interfaces  
  • configure manually IGMP multicast group membership on router 2 for testing.
  • configure router 2 loopback (120.1.1.1) a static rendezvous point (RP) advertise in OSPF 100 with the mask 32.
  • configure RP address on all the routers. 



R1#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol

FastEthernet0/0        10.1.1.1        YES NVRAM  up                    up
Serial3/0                    1.1.1.1         YES NVRAM  up                    up
Serial3/2                    3.3.3.2         YES NVRAM  up                    up


R2#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol

FastEthernet0/0        20.1.1.1        YES NVRAM  up                    up
Serial3/0                    1.1.1.2         YES NVRAM  up                    up
Serial3/1                    2.2.2.1         YES NVRAM  up                    up
Loopback0              120.1.1.1       YES NVRAM  up                    up



R3#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol

FastEthernet0/0        30.1.1.1        YES NVRAM  up                    up
Serial3/1                     2.2.2.2         YES NVRAM  up                    up
Serial3/2                    3.3.3.1         YES NVRAM  up                    up
Serial3/3                    4.4.4.2         YES NVRAM  up                    up

R4#show ip interface brief
Interface              IP-Address      OK? Method Status                Protocol

FastEthernet0/0        40.1.1.1        YES NVRAM  up                    up
Serial3/3                    4.4.4.1         YES NVRAM  up                    up


R1(config)#router ospf 100
R1(config-router)#network 10.0.0.0 0.255.255.255 area 0
R1(config-router)#network 1.0.0.0 0.255.255.255 area 0
R1(config-router)#network 3.0.0.0 0.255.255.255 area 0
R1(config-router)#exit


*Nov 19 20:58:03.523: %OSPF-5-ADJCHG: Process 100, Nbr 120.1.1.1 on Serial3/0 from LOADING to FULL, Loading Done

*Nov 19 20:58:52.515: %OSPF-5-ADJCHG: Process 100, Nbr 30.1.1.1 on Serial3/2 from LOADING to FULL, Loading Done




R2(config)#router ospf 100
R2(config-router)#network 20.0.0.0 0.255.255.255 area 0
R2(config-router)#network 2.0.0.0 0.255.255.255 area 0
R2(config-router)#network 1.0.0.0 0.255.255.255 area 0
R2(config-router)#exit

*Nov 19 20:58:03.611: %OSPF-5-ADJCHG: Process 100, Nbr 3.3.3.2 on Serial3/0 from LOADING to FULL, Loading Done

*Nov 19 20:58:57.567: %OSPF-5-ADJCHG: Process 100, Nbr 30.1.1.1 on Serial3/1 from LOADING to FULL, Loading Done

 R3(config)#router ospf 100
R3(config-router)#network 30.0.0.0 0.255.255.255 area 0
R3(config-router)#network 3.0.0.0 0.255.255.255 area 0
R3(config-router)#network 2.0.0.0 0.255.255.255 area 0
R3(config-router)#network 4.0.0.0 0.255.255.255 area 0
R3(config-router)#exit

*Nov 19 20:58:52.531: %OSPF-5-ADJCHG: Process 100, Nbr 3.3.3.2 on Serial3/2 from LOADING to FULL, Loading Done

*Nov 19 20:58:57.443: %OSPF-5-ADJCHG: Process 100, Nbr 120.1.1.1 on Serial3/1 from LOADING to FULL, Loading Done

R4(config)#router ospf 100
R4(config-router)#network 40.0.0.0 0.255.255.255 area 0
R4(config-router)#network 4.0.0.0 0.255.255.255 area 0
R4(config-router)#exit

*Nov 19 21:01:57.783: %OSPF-5-ADJCHG: Process 100, Nbr 30.1.1.1 on Serial3/3 from LOADING to FULL, Loading Done



R1(config)#ip multicast-routing

R1(config)#interface serial 3/0
R1(config-if)#ip pim sparse-mode
R1(config-if)#exit

R1(config-if)#interface serial 3/2
R1(config-if)#ip pim sparse-mode
R1(config-if)#exit

R1(config)#interface fastEthernet 0/0
R1(config-if)#ip pim sparse-mode
R1(config-if)#exit

*Nov 19 21:07:27.535: %PIM-5-DRCHG: DR change from neighbor 0.0.0.0 to 10.1.1.1 on interface FastEthernet0/0





R2(config)#ip multicast-routing

R2(config)#interface serial 3/0
R2(config-if)#ip pim sparse-mode
R2(config-if)#exit

R2(config)#interface serial 3/1
R2(config-if)#ip pim sparse-mode
R2(config-if)#exit

R2(config)#interface fastEthernet 0/0
R2(config-if)#ip pim sparse-mode
R2(config-if)#exit


R3(config)#ip multicast-routing

R3(config)#interface serial 3/1
R3(config-if)#ip pim sparse-mode
R3(config-if)#exit

R3(config)#interface serial 3/2
R3(config-if)#ip pim sparse-mode
R3(config-if)#exit

R3(config)#interface serial 3/3
R3(config-if)#ip pim sparse-mode
R3(config-if)#exit

R3(config)#interface fastEthernet 0/0
R3(config-if)#ip pim sparse-mode
R3(config-if)#exit

R4(config)#ip multicast-routing

R4(config)#interface serial 3/3
R4(config-if)#ip pim sparse-mode
R4(config-if)#exit


R4(config)#interface fastEthernet 0/0
R4(config-if)#ip pim sparse-mode
R4(config-if)#exit

*Nov 19 21:12:44.031: %PIM-5-DRCHG: DR change from neighbor 0.0.0.0 to 40.1.1.1 on interface FastEthernet0/0


R1#show ip pim interface

Address          Interface                Ver/   Nbr    Query  DR     DR
                                                   Mode   Count  Intvl  Prior
10.1.1.1         FastEthernet0/0    v2/S   0      30     1      10.1.1.1
1.1.1.1          Serial3/0                v2/S   1      30     1      0.0.0.0
3.3.3.2          Serial3/2                v2/S   1      30     1      0.0.0.0


R2(config)#router ospf 100
R2(config-router)#network 120.0.0.0 255.0.0.0 area 0
R2(config-router)#exit

R1(config)#ip pim rp-address 120.1.1.1
R1(config)#exit

*Nov 19 22:18:17.103: %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to up

R2(config)#interface loopback 0
R2(config-if)#ip ospf network point-to-point
R2(config-if)#exit


*Nov 19 22:18:16.771: %PIM-6-INVALID_RP_JOIN: Received (*, 224.0.1.40) Join from 1.1.1.1 for invalid RP 120.1.1.1

R2(config)#ip pim rp-address 120.1.1.1

*Nov 19 22:18:33.263: %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to up

*Nov 19 22:18:33.375: %LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel1, changed state to up



R2(config)#interface fastEthernet 0/0
R2(config-if)#ip igmp join-group 224.2.2.2
R2(config-if)#exit


(let see some show command for verification)

 From Router 1




 From Router 2



  From Router 3




 From Router 4



 From Router 2




 From Router 1



 From Router 2

 From Router 3



 From Router 4





Wednesday, 13 November 2019

What is Reverse Path Forwarding (RPF) check?


To prevent loops, router do not forward multicast out the same interface on which they were received. Multicast routers use a reverse path forwarding (RPF) check to prevent loops. A multicast router does not forward any multicast packet unless the packet passes the RPF check.


The RPF check compares incoming packets with the unicast routing table to determine if a packet is arriving on the correct interface.


The issue of receiving duplicate packets, Cisco routers perform a reverse path forwarding (RPF)
Check to determine whether a multicast packet is entering a router on the correct interface





An RPF check examines the source address of an incoming packet and check it against the router’s uni-cast routing table to see what interface should be used to get back to the source network. If the incoming multicast packet is using that interface, the RPF  check passes, and the packet is forwarded.
If the multicast packet is coming in a different interface, the RPF check fails, and packet is discarded.

Configuration click here

PIM Sparse Mode

PIM Sparse Mode  ( PIM-SM )  PIM  Sparse Mode explicitly builds unidirectional shared trees rooted at a ( RP ) rendezvous point per...