IGMP static joins on IOS XR

[simone.c]

Hi all,

in IOS we have the interface command:

ip igmp static-group class-map xyz, where xyz is a 'class-map type multicast-flows'. This is used to statically join many groups with one single command.

In IOS XR (7.6.2, ASR9k) I am only able to successfully join one group at a time (e.g. static-group 239.0.0.1), but I want to statically join a lot of groups with one single command. I have tried, within IGMP configuration mode, this line but it doesn't seem to work:

static-group 224.0.99.0 inc-mask 0.0.0.255 count 255

I would expect this command to cause a static join for groups from 224.0.99.0 to 224.0.99.255, but what I see in reality is a lot of *,G being built for groups outside of this range. This is an excerpt from the mrib (the IGMP interface in question is listed in the OIL):

(*,224.1.154.8)
(*,224.1.155.7)
(*,224.1.156.6)
(*,224.1.157.5)
(*,224.1.158.4)
(*,224.1.159.3)
(*,224.1.160.2)

This is the IGMP config:

router igmp
version 2
!
vrf myvrf
interface GigabitEthernet0/1/1/6
static-group 224.0.99.0 inc-mask 0.0.0.255 count 255
version 2
router enable

Any hint is really appreciated. Thank you!

[Harold Ritter · Accepted solution]

Hi @simone.c ,

The reason it doesn't start with 224.0.99.0 is that this is a reserved multicast block. Try the same command with an unreserved block and it should work. Also if you want the increment to be 1, you need to configure the inc-mask as 0.0.0.1.

router igmp
interface GigabitEthernet0/0/0/0
static-group 239.1.1.1 inc-mask 0.0.0.1 count 10
router enable
!

RP/0/RP0/CPU0:XR1#sh ip igmp groups

Fri Jan 20 15:36:57.599 UTC

IGMP Connected Group Membership
Group Address Interface Uptime Expires Last Reporter
239.1.1.1 GigabitEthernet0/0/0/0 00:11:31 never 0.0.0.0
239.1.1.2 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.3 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.4 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.5 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.6 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.7 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.8 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.9 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
239.1.1.10 GigabitEthernet0/0/0/0 00:05:21 never 0.0.0.0
RP/0/RP0/CPU0:XR1#

Regards,

[simone.c]

Hi Harold,

thanks for your feedback. Actually it works also with reserved MC addresses (what I showed before was just a small excerpt of the *,G being built, I couldn't figure out how it was selecting those MC groups).

The problem was with me not understanding the inc-mask concept - it is the first time I encounter it. I thought inc-mask works like a wildcard mask. After changing 0.0.0.255 to 0.0.0.1 it works as expected.

Thanks a lot!

[Harold Ritter]

You are very welcome @simone.c