From: Huan Pham (huan.pham@valuenet.com.au)
Date: Tue Jan 15 2008 - 21:31:58 ARST
Hi GS,
I have difficulty understanding the "debug ip mpacket" command. My
understanding is that it should show all the multicast packets that a router
receives, sends or forwards. It seems that this is not the case! I can only
see the multicast packets when the router run multicast routing AND join a
multicast group.
- If a router runs unicast and join a multicst group (pretending as a PC
listening to multicast traffic), the debug ip packets DOES NOT show any
multicast packets.
- If a router runs multicast and does not join any group (a transit
multicast router), the debug ip packets DOES NOT show anything either.
- In the transit Multicast router (R2), I can not see the multicast packet
using "debug ip packet". In the destination host (R4, running only Unicast)
I can see multicast packets using "debug ip packet".
I would like to know if this is a normal behavior or I miss something.
My config is below. I run PIM Dense mode. The multicast forwarding works
fine.
Thanks,
TOPOLOGY
R1 (src) --------- R3 ----------------R2 -------------R4 (dest)
13.0.0.0/8 23.0.0.0/8 24.0.0.0/8
R1#
!
! This is to generate Multicast traffic
ip sla monitor 1
type udpEcho dest-ipaddr 224.1.1.1 dest-port 12345 source-ipaddr 13.0.0.1
control disable
timeout 0
frequency 5
ip sla monitor schedule 1 life forever start-time now
!
!
interface FastEthernet0/0
ip address 13.0.0.1 255.0.0.0
!
router ospf 1
network 0.0.0.0 255.255.255.255 area 0
R3#
!
no ip domain lookup
ip multicast-routing
!
!
!
interface FastEthernet0/0
ip address 13.0.0.3 255.0.0.0
ip pim dense-mode
!
interface Serial1/3
ip address 23.0.0.3 255.0.0.0
ip pim dense-mode
!
router ospf 1
network 0.0.0.0 255.255.255.255 area 0
R2#
ip multicast-routing
!
interface FastEthernet0/0
ip address 24.0.0.2 255.0.0.0
ip pim dense-mode
!
interface Serial1/1
ip address 23.0.0.2 255.0.0.0
ip pim dense-mode
!
router ospf 1
log-adjacency-changes
network 0.0.0.0 255.255.255.255 area 0
!
R4#
!
interface Ethernet0/0
ip address 24.0.0.4 255.0.0.0
ip igmp join-group 224.1.1.1
!
!
router ospf 1
network 0.0.0.0 255.255.255.255 area 0
R3#sh ip mroute 224.1.1.1
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
L - Local, P - Pruned, R - RP-bit set, F - Register flag,
T - SPT-bit set, J - Join SPT, M - MSDP created entry,
X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
U - URD, I - Received Source Specific Host Report, Z - Multicast
Tunnel
Y - Joined MDT-data group, y - Sending to MDT-data group
Outgoing interface flags: H - Hardware switched, A - Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
(*, 224.1.1.1), 00:35:28/stopped, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Serial0/3, Forward/Dense, 00:32:37/00:00:00
FastEthernet0/0, Forward/Dense, 00:34:02/00:00:00
(13.0.0.1, 224.1.1.1), 00:35:25/00:02:59, flags: LT
Incoming interface: FastEthernet0/0, RPF nbr 0.0.0.0
Outgoing interface list:
Serial0/3, Forward/Dense, 00:32:37/00:00:00
R2#sh ip mroute 224.1.1.1
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
L - Local, P - Pruned, R - RP-bit set, F - Register flag,
T - SPT-bit set, J - Join SPT, M - MSDP created entry,
X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
U - URD, I - Received Source Specific Host Report, Z - Multicast
Tunnel
Y - Joined MDT-data group, y - Sending to MDT-data group
Outgoing interface flags: H - Hardware switched, A - Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode
(*, 224.1.1.1), 00:29:46/stopped, RP 0.0.0.0, flags: DC
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 00:27:21/00:00:00
Serial0/1, Forward/Dense, 00:29:46/00:00:00
(13.0.0.1, 224.1.1.1), 00:29:45/00:02:56, flags: T
Incoming interface: Serial0/1, RPF nbr 23.0.0.3
Outgoing interface list:
FastEthernet0/0, Forward/Dense, 00:27:21/00:00:00
R2#debug ip mpacket
IP multicast packets debugging is on
R2#
! NOTHING SHOWS UP
R2#
R2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R2(config)#int s0/1
R2(config-if)#ip igmp join 224.1.1.1
R2(config-if)#
R2#
Jan 16 12:01:48.771: %SYS-5-CONFIG_I: Configured from console by console
Jan 16 12:01:51.215: IP(0): s=13.0.0.1 (Serial0/1) d=224.1.1.1
(FastEthernet0/0) id=0, ttl=253, prot=17, len=44(44), mforward
Jan 16 12:01:56.215: IP(0): s=13.0.0.1 (Serial0/1) d=224.1.1.1
(FastEthernet0/0) id=0, ttl=253, prot=17, len=44(44), mforward
Jan 16 12:02:01.215: IP(0): s=13.0.0.1 (Serial0/1) d=224.1.1.1
(FastEthernet0/0) id=0, ttl=253, prot=17, len=44(44), mforward
Jan 16 12:02:06.215: IP(0): s=13.0.0.1 (Serial0/1) d=224.1.1.1
(FastEthernet0/0) id=0, ttl=253, prot=17, len=44(44), mforward
Jan 16 12:02:11.211: IP(0): s=13.0.0.1 (Serial0/1) d=224.1.1.1
(FastEthernet0/0) id=0, ttl=253, prot=17, len=44(44), mforward
Jan 16 12:02:16.211: IP(0): s=13.0.0.1 (Serial0/1) d=224.1.1.1
(FastEthernet0/0) id=0, ttl=253, prot=17, len=44(44), mforward
Jan 16 12:02:21.211: IP(0): s=13.0.0.1 (Serial0/1) d=224.1.1.1
(FastEthernet0/0) id=0, ttl=253, prot=17, len=44(44), mforward
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