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cramer
Premium Member
join:2007-04-10
Raleigh, NC
Westell 6100
Cisco PIX 501

cramer to HELLFIRE

Premium Member

to HELLFIRE

Re: [Config] AP1242AG question

It's a bug. It simply doesn't handle multicast correctly. (common failing of wireless gear.)

IGMP snooping allows the device doing the snooping to filter multicast to what's actually needed on a link. Without this "hack", all multicast traffic is flooded as broadcast traffic.

DarkLogix
Texan and Proud
Premium Member
join:2008-10-23
Baytown, TX

DarkLogix

Premium Member

said by cramer:

It's a bug. It simply doesn't handle multicast correctly. (common failing of wireless gear.)

IGMP snooping allows the device doing the snooping to filter multicast to what's actually needed on a link. Without this "hack", all multicast traffic is flooded as broadcast traffic.

My understanding is IGMP snooping trades CPU for bandwidth.
It builds a table of what is listening for multicast and then if something sends a multicast it only sends it to those listening, thus saving bandwidth on the non-listening ports. (kind of like a switch to a hub)

but on the AP1242AG (possibly other models too, and possibly fixed in a newer IOS) it just dead ends multicast at the radio, so even another wifi device won't hear the multicast.

By turning snooping off (the default is on, thus why the command didn't show up in the running config, but the no form does show up in the running config)

Its just a matter of a bug that IGMP snooping doesn't work on the AP.
HELLFIRE
MVM
join:2009-11-25

HELLFIRE to cramer

MVM

to cramer
You wouldn't happen to have a bugID would you cramer? Funny that it still hasn't been fixed yet, but there's been wierder ones...

Regards

DarkLogix
Texan and Proud
Premium Member
join:2008-10-23
Baytown, TX

DarkLogix

Premium Member

said by HELLFIRE:

You wouldn't happen to have a bugID would you cramer? Funny that it still hasn't been fixed yet, but there's been wierder ones...

Regards

do we know if its been fixed?
I'm running the IOS listed below, but I think theres a newer version, but I don't have access to download it I don't think.
c1240-k9w7-mx.124-10b.JDA
cramer
Premium Member
join:2007-04-10
Raleigh, NC
Westell 6100
Cisco PIX 501

1 edit

cramer

Premium Member

Depends on who you ask... 12.4.10b-JDA3 (GD) is the lastest on that path. Cisco lists 12.4.21a-JY as the latest, but 12.4.25d-JA2 is the last image published (14-Sep-2012) I'm running 12.4.25d-JA -- I guess I should test this.

And no, I have no clue what the bugID(s) may be. (if they exist, or if they're visible outside Cisco.)

[EDIT]
Tested. And it works... well as badly as I expect multicast streams to "work" via wireless. (that being even 1.5Mbps is too fast for it)
ap#show ip igmp snooping groups vlan 1
Vlan Group Version Port List
---------------------------------------------------------
1 239.255.0.1 v2 Dot11Radio0
1 239.255.255.250v2 Dot11Radio0

239.255.0.1 is the HDHR (streaming PBS) [For the record, it won't unicast a 19Mbps stream either; 13-14 works]