From: Paul Cosgrove (paul.cosgrove@heanet.ie)
Date: Sun Jun 01 2008 - 05:57:20 ART
Can think of a few possible reasons why you may prefer an IGMP access
group over an ip acl.
- IGMP access-group may give better performance. An normal acl would
have to inspect all incoming ip traffic whereas an igmp access-group
probably just inspects igmp traffic on its way to the CPU.
- PIMv1 used the same ip protocol number as IGMP. If an IGMP
access-group does not impact PIMv1 (and I've never tested it), that may
be a rarely required benefit. A normal acl would have to be configured
to permit reqired traffic for either protocol (if anyone still uses v1).
- IGMP access group, referring to an extended acl, is able to select SSM
sources. So using this method helps standardise the configs regardless
of igmp version.
Paul.
keith tokash wrote:
> That depends on what you consider "significant". The IGMP acl will block
> hosts from joining a group, while the IP acl will block packets to that IP
> address (group). One works on IGMP, the other on IP. Whether that's
> significant depends on whether you run up against some restriction that
> prohibits you from using one, forcing you to use the other. I don't mean a
> lab restriction like, where someone says, "Don't use an IP acl", I mean a real
> one. Personally I can't think of one, but that doesn't mean it isn't out
> there.
>
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>> Date: Sat, 31 May 2008 17:53:57 -0400
>> From: lhall@setnine.com
>> To: ccielab@groupstudy.com
>> Subject: igmp vs ip access-group
>>
>> is there any significant difference between using
>> ip igmp access-group <std acl> and blocking the same traffic
>> using ip access-group <ext acl blocking igmp>? if theres
>> not i dont see why they would even have the command
>> 'ip igmp access-group' so I thought there must be something, i
>> cant find anything and it would be nice to know definitively.
>>
>>
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