From: Bit Gossip (bit.gossip@chello.nl)
Date: Thu Aug 23 2007 - 10:46:16 ART
I agree that this is perfect behaviour in the role of a multicast routerm, but
if it has to be a simple multicast host that sends IGMP reports and replies to
the ping, the only thing necessary is really 'ip igmp join-group ...'
So I don't understand why it can not send reports unless also pim is enabled
....
Furthermore, if I use a router instead of a Cat3550 as a simple multicast
receiver, without configuring 'ip multicast-routing' and pim but only the 'ip
igmp join group ', it works just fine.
This is a major difference in behavior (inconsistency) that is important to
keep in mind during the exam: can save big troubleshooting time.
This is what I used for the testing:
Router: (C7200-IK9S-M), Version 12.4(12)
Switch: (C3550-IPSERVICESK9-M), Version 12.2(25)SEE3
Any volonteer that can test the Cat3560 ......
----- Original Message -----
From: Herbert Maosa
To: Bit Gossip
Cc: ccielab@groupstudy.com
Sent: Thursday, August 23, 2007 1:27 PM
Subject: Re: Cat3550 as mcast receiver
I dont think it is complicated, I have not seen it behave any differently
from a router. In order to receive the traffic for the group, the loopback
interface must be added to the OIL. PIM is what builds the tree, so the
interface can not be added to the OIL unless you enable PIM on the interface
apart from using ip igmp joinj group. This behavior is the same even from
routers and is expected.
Then, if you are using PIM sparse mode, you need an RP. You will learn the
RP either statically or dynamically.
Once you learn the RP, you need to have reachability to both the RP and the
multicast source. You must therefore have some good routing on the switch to
give you this reachability inorder for the RPF checks to pass.
It looks to me like your switch is behaving as it should, unless I am
missing something.
Herbert.
On 8/23/07, Bit Gossip < bit.gossip@chello.nl> wrote:
Experts,
in many practice-labsit is required to configure one of the Cat3550 as
multicast receiver for certain groups so that it replies to ping send to
that
particular group. This is done using 'ip igmp join-group 224.224.224.224'
but
to me this never works, see below.
If I configure only 'ip igmp join-group 224.224.224.224' I notice from
neighbor routers that the Cat3550 doesn't actually send any IGMP report
for
the group.
So I enable 'ip multicast-routing' and 'ip sparse-mode' on the interface
and
at this point IGMP reports are finally sent.
But still Cat3550 doesn't reply to ping complaing of not being able to RPF
to
the RP, which makes sense because no RP has been defined. Actually I
don't
want to define any RP on this switch because I want it to behave just like
a
dumb host and not like a multicast router.
S4#ping 224.224.224.224
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.224.224.224, timeout is 2 seconds:
1d01h: IP(0): MAC sa= 000b.464a.4180 (Vlan106), IP last-hop=10.1.68.10
1d01h: IP(0): IP tos=0x0, len=100, id=10, ttl=254, prot=1
1d01h: IP(0): s=10.1.68.10 (Vlan106) d= 224.224.224.224 id=10, ttl=254,
prot=1,
len=114(100), RPF lookup failed for source or RP.
I tried to put a static mroute but it doesn't fix the problem, so to make
it
happy I configure itself as a dummy RP and finally it replies to the
multicast
ping
S4#ping 224.224.224.224
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 224.224.224.224, timeout is 2 seconds:
Reply to request 0 from 10.1.68.10, 4 ms
An alternative to configuring a dummy RP is to configure the interface in
dense mode; this also works.
Is it really so complicated to convince this Cat 3550 to reply to the ping
or
I am missing something?
What about Cat3560, I can not test it because I don't have it?
S4#show ver
Cisco IOS Software, C3550 Software (C3550-IPSERVICESK9-M), Version
12.2(25)SEE3, RELEASE SOFTWARE (fc2)
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--
Kindest regards,
hm
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