Re: IGMP multicast on 4000

jjkruege · ‎07-31-2003

I have a Cisco 4000 with Sup3 and an 8 port GBIC module and a 48 port 10/100/1000 module. Each gig fiber connection goes to a 3com switch in each wiring closet.

All the servers and some PC's are connected to the 48 port 10/100/1000 module. The Ghost server is connected to this module. It performs multicast sessions with many PC's to reimage them. I believe that IGMP snooping is on by default on the 4000. Currently all ports are in VLAN1. There is currently no routing occurring.

We have had several users complaining of losing their network connection and slow performance and different times during the day. We think that it may be related to the Ghosting. I thought that IGMP snooping on the 4000 would keep the Ghost multicast traffic off the rest of the network and only flood the traffic to the ports that have a PC requesting the multicast session. I understand that the 3com switches will be flooded across all ports, but I thought that the gig uplinks to other closets that do not have any PC's requesting the session would not be flooded. The sho int count below seems to show that all multicast traffic is being sent to all ports.

THe Ghost server port 3/6 shows 17520890 multicast packets were sent into the switch port interface. Most other ports show about 17600000 multicast packets being sent out the interface to each of the end nodes. I thought that IGMP snooping would help lower this. I have done this with a 6500 and it seemed to work well.

Am I mistaken on how IGMP snooping works on the 4000? Is routing across VLAN's required for IGMP snooping to work? I have included parts of my config below also. It is pretty basic. Could the secondary address on VLAN 1 mess up the IGMP snooping?

Thanks,

Josh Krueger

!

interface GigabitEthernet1/1

description 2/1 A Floor 2 Closet 1 Module A

no logging event link-status

no snmp trap link-status

!

interface GigabitEthernet1/2

description 2/1 B Floor 2 Closet 1 Module B

no logging event link-status

no snmp trap link-status

!

interface GigabitEthernet2/1

description 2/2 A Floor 2 Closet 2 Module A

no logging event link-status

!

interface GigabitEthernet3/20

no logging event link-status

spanning-tree portfast

!

interface GigabitEthernet3/21

no logging event link-status

spanning-tree portfast

!

interface GigabitEthernet3/22

no logging event link-status

spanning-tree portfast

!

interface GigabitEthernet3/23

no logging event link-status

spanning-tree portfast

!

interface GigabitEthernet3/24

no logging event link-status

spanning-tree portfast

!

interface Vlan1

ip address 172.16.1.2 255.255.0.0 secondary

ip address 172.16.1.1 255.255.0.0

no ip redirects

no logging event link-status

!

router rip

version 1

network 172.16.0.0

distribute-list 10 in

!

ip default-gateway 172.16.1.1

ip classless

ip route 0.0.0.0 0.0.0.0 172.16.1.11

no ip http server

!

IAA-Core-C4006S3#sho int count

Port InBytes InUcastPkts InMcastPkts InBcastPkts

Gi1/1 16325372950 24572181 5652 134493

Gi1/2 10933607240 21218554 4031 100444

Gi2/1 1541683017 5866059 6657 107440

Gi2/2 3350242339 10139781 7939 10064

Gi2/3 402272408 1047090 133 29708

Gi2/4 1331344406 4452999 4119 150453

Gi2/5 1044931874 3193459 606 66534

Gi2/6 444913038 1635249 112 21344

Gi3/1 1167241510 3169072 10609 11601

Gi3/2 866845494 3287399 13906 10093

Gi3/3 2794578 11279 4301 826

Gi3/4 3585520368 3962838 1076 35395

Gi3/5 16877889772 15105675 1412 7469

################################################ Ghost server

Gi3/6 26537616524 6502679 17520890 3850

################################################

Port OutBytes OutUcastPkts OutMcastPkts OutBcastPkts

Gi1/1 31061073015 13018032 17688029 742526

Gi1/2 37869238829 19773045 17689652 776572

Gi2/1 30924227200 6264284 17687023 769575

Gi2/2 40918051538 12569918 17685742 866878

Gi2/3 26950883798 1119095 17693052 844858

Gi2/4 28924724717 5114533 17689561 726528

milan.kulik · ‎07-31-2003

Hi,

i agree IGMP snooping should be enabled by default.

Have you checked with "sh ip igmp snooping" or "sh ip igmp int" that it is really working?

Regards,

Milan

jjkruege · ‎08-01-2003

Sorry, I should have mentioned that I had checked that. I did check that and it appeared to be globally enabled. Results are below.

Although, now that I look at it more closely, it looks like IGMP is disabled on VLAN 1. Am I reading that right? Do I just need to type "ip igmp" on that vlan interface to get it going? Is it required to have multicast routing turned on for IGMP to function on a vlan?

Thanks,

Josh Krueger

IAA-Core-C4006S3#sho ip igmp snoop

vlan 1

----------

IGMP snooping is globally enabled

IGMP snooping TCN solicit query is globally disabled

IGMP snooping global TCN flood query count is 2

IGMP snooping is enabled on this Vlan

IGMP snooping immediate-leave is disabled on this Vlan

IGMP snooping mrouter learn mode is pim-dvmrp on this Vlan

IGMP snooping is running in IGMP_ONLY mode on this Vlan

IGMP snooping report suppression is enabled on this Vlan

IAA-Core-C4006S3#

IAA-Core-C4006S3#sho ip igmp int

Vlan1 is up, line protocol is up

Internet address is 172.16.1.1/16

IGMP is disabled on interface

Multicast routing is disabled on interface

Multicast TTL threshold is 0

No multicast groups joined

GigabitEthernet1/1 is up, line protocol is up