Re: PIM Multicast simple question

From: Chen Kwong Wai William (kwchen@netvigator.com)
Date: Sun Nov 02 2003 - 21:28:47 GMT-3


Hi,

    Just play around with a 2500, and found the following:

! IP multicast-routing is enable
R5#sh run | in multicast
ip multicast-routing

! IGMP is not automatically enable on E0
R5#sh ip igmp int e0
Ethernet0 is up, line protocol is up
  Internet address is 192.168.0.100/24
  IGMP is disabled on interface
  Multicast routing is disabled on interface
  Multicast TTL threshold is 0
  No multicast groups joined

! Enable PIM on E0, enable the IGMP automatically
R5#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R5(config)#int e0
R5(config-if)#ip pim sparse-dense-mode
R5(config-if)#end
R5#sh ip igmp int e0
Ethernet0 is up, line protocol is up
  Internet address is 192.168.0.100/24
  IGMP is enabled on interface
  Current IGMP host version is 2
  Current IGMP router version is 2
  IGMP query interval is 60 seconds
  IGMP querier timeout is 120 seconds
  IGMP max query response time is 10 seconds
  Last member query response interval is 1000 ms
  Inbound IGMP access group is not set
  IGMP activity: 1 joins, 0 leaves
  Multicast routing is enabled on interface
  Multicast TTL threshold is 0
  Multicast designated router (DR) is 192.168.0.100 (this system)
  IGMP querying router is 192.168.0.100 (this system)
  Multicast groups joined (number of users):
      224.0.1.40(1)

! Disable PIM on E0, automatically disable IGMP on E0
R5#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R5(config)#int e0
R5(config-if)#no ip pim sparse-dense-mode
R5(config-if)#end
R5#sh ip igmp int e0
Ethernet0 is up, line protocol is up
  Internet address is 192.168.0.100/24
  IGMP is disabled on interface
  Multicast routing is disabled on interface
  Multicast TTL threshold is 0
  No multicast groups joined

--- William Chen

----- Original Message -----
From: "ccie2be" <ccie2be@nyc.rr.com>
To: "Group Study" <ccielab@groupstudy.com>
Sent: Sunday, November 02, 2003 10:38 PM
Subject: PIM Multicast simple question

> Hi all,
>
> When Multicast is enabled on a router, by default, IGMP is enabled on Lan
> interfaces. That being the case, is it necessary to also enter the
interface
> command,
>
> ip pim <dense-mode|sparse-mode| sparse-dense-mode>,
>
> when there are only multicast hosts attached to that interface and no
> possibility of other routers connecting to that interface?
>
> For example, if you have the following multicast network,
>
> R2------R1(E0)------switch------mcast hosts only
>
> does, ip pim <dense-mode|sparse-mode| sparse-dense-mode>
>
> need to be entered on the E0 interface of R1? Please explain why or why
not.
>
> Thanks, dt
>
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