Soldiers of ccie battle !
i have a basic question on multicast registration process.
how rpf check is done on unicasted register messages on RP ??
*topology *
23.0.0.0
34.0.0.0
R1============ R2 [ fa0/1----------------- fa0/1] R3 [f0/0
==============f0/0] R4
12.0.0.0 s0/1------------------ s0/1
34.0.0.0
R1
*interface FastEthernet0/0 ip address 12.0.0.1 255.255.255.0 ip pim
dr-priority 100!router eigrp 100 network 0.0.0.0 no auto-summary*
R2
*interface FastEthernet0/0 ip address 12.0.0.2 255.255.255.0 ip pim
sparse-mode! interface FastEthernet0/1 ip address 23.0.0.2 255.255.255.0 ip
pim sparse-mode!router eigrp 100 network 0.0.0.0 no auto-summary*
R3
*interface Loopback0 ip address 150.1.3.3 255.255.255.0 ip pim
sparse-mode!interface FastEthernet0/0 ip address 34.0.0.3 255.255.255.0 ip
pim sparse-mode!interface FastEthernet0/1 ip address 23.0.0.3
255.255.255.0 ip pim sparse-mode*
!
*interface Serial1/0 ip address 32.0.0.3 255.255.255.0 serial restart-delay
0*
!! pim is not running on s1/0 to understand RPF behavior of register
message!!
R4:
*interface FastEthernet0/0 ip address 34.0.0.4 255.255.255.0 ip igmp
join-group 224.1.1.1!router eigrp 100 network 0.0.0.0 no auto-summary*
Multicast info:
we will switch DR between R1 and R2 .
R3 is the RP.
RP assignment is static
case 1 :
when R1 is source and DR at same time.
R1#show ip pim interface fa0/0
Address Interface Ver/ Nbr Query DR DR
Mode Count Intvl Prior
12.0.0.1 FastEthernet0/0 v2/S 1 30 100
12.0.0.1
on R2 lets add a static route to make traffic arrive on non rpf interface
R2(config)#ip route 150.1.3.3 255.255.255.255 Serial1/0
lets trace from R1
R1#traceroute 150.1.3.3
Type escape sequence to abort.
Tracing the route to 150.1.3.3
1 12.0.0.2 28 msec 32 msec 8 msec
2 32.0.0.3 28 msec 36 msec 4 msec ==.>s1/0
*intention here is to make register messages on RP come in a NON-RPF
interface. *
on RP ie R3 lets check RPF neighbor for multicast source
R3#show ip rpf 12.0.0.1
RPF information for ? (12.0.0.1)
RPF interface: *FastEthernet0/1*
RPF neighbor: ? (23.0.0.2)
RPF route/mask: 12.0.0.0/24
it is fa0/1
*now the Reigstarion process:*
R1#ping 224.1.1.1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.1.1.1, timeout is 2 seconds:
*Reply to request 0 from 34.0.0.4, 188 ms*
*Mar 1 00:10:50.583: PIM(0): Received v2 Register *on Serial1/0* from
12.0.0.1
*Mar 1 00:10:50.583: for 12.0.0.1, group 224.1.1.1
*Mar 1 00:10:50.587: PIM(0): Insert (12.0.0.1,224.1.1.1) join in nbr
23.0.0.2's queue
*Mar 1 00:10:50.591: PIM(0): Forward decapsulated data packet for
224.1.1.1 on
though their is a disconnect from the rpf neighbor and where the
messages
are coming in , but still no rfp failure
case 2: switch DR to R2
R1(config-if)#no ip pim dr-priority 100
*Mar 1 01:05:26.571: %PIM-5-DRCHG: DR change from neighbor 12.0.0.1 to
12.0.0.2 on interface FastEthernet0/0
R1#show ip pim int fa0/0
Address Interface Ver/ Nbr Query DR DR
Mode Count Intvl Prior
12.0.0.1 FastEthernet0/0 v2/S 1 30 1
*12.0.0.2*
clearing all states
R1#clear ip mroute *
R2#clear ip mroute *
R3#clear ip mroute *
on DR ie on R2 NOW
R2#
*Mar 1 01:07:42.747: IP(0): s=12.0.0.1 (FastEthernet0/0) d=224.1.1.1
id=26, ttl=254, prot=1, len=114(100),* RPF lookup failed for source or RP*
CONCLUSION :
*it is not RP who is checking RPF for register message, but DR.
unless their is no source route for mutlicast source on RP *
*Also the register message is unicast at the end. on RP . *
*Please appreciate your replies to understand the process better !!*
*i did not find any solid reference even on rfc 4061 *
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