From: Duongla (duongla@vnn.vn)
Date: Fri Sep 02 2005 - 14:15:14 GMT-3
Hi group,
I have tried the following scenario on 4 Cisco 2600:
R1,R2 and R3 are connected via multipoint frame-relay (physical interface), R2
is the HUB.
Routing is running normally, all routers can reach all subnets.
R2 f0/0 connect to R4 whichs is a test router, responsible for genarating
multcast traffic.
R1,R2,R3 are all configured with multicast PIM sparse mode and loopback
interface of R3
is configured manually on 3 routers as RP.
R1f0/0 and R3 f0/0 are configured to join group 239.1.1.1
Before PING 239.1.1.1 from R4, the mroute tables int 3 router are in normal
state:
R1,R3 send Join msg to RP which is R2, so R2 has a (*,239.1.1.1) entry in its
mroute table.
For first PING 239.1.1.1 from R4, both R1 and R3 reply.
From second PING, just R3 replies.
Do debug ip mpacket fastswitch 239.1.1.1, I saw R2 forwarded the mcast packet
from R4 out serial0/0
(the frame relay port, connecting to R1 and R3) but just R3 got the packet and
sent PING echo-reply.
One interesting notice is: router with higher IP address of frame relay
interface receives the PING mcast packet.
In this case R3.
If I turn off fast switching on R2 s0/0 then both R1 and R3 receive mcast
packet.
Can anyone help clarify the above behaviour ?
Thanks in advance.
Duongla
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