Introduction
Contents
AlliedWare OS
Snooper timer values
Why convergence takes so long without query solicitation
Enabling query solicitation on multiple switches in a looped topology
Querier timer values
Products and software versions this note applies to
IGMP feature
For most examples in this How To Note, we used
z one AT-8948 switch, with Software Version
z two Rapier 24i switches, with Software Version
Queriers and Snoopers
IGMP overview
Messages
Choosing group addresses
Page 8 AlliedWare OS How To Note IGMP
Avoid x.0.0.y, x.0.1.y, x.128.0.y, and x.128.1.y
Example
IGMP snooping
Page 10 AlliedWare OS How To Note IGMP
X Configure switch
X Configure switch
X Configure switch
process
Explanation of IGMP snooping
igmpsnooping on the Snooper
Using Show command output to investigate IGMP state
Page 13 AlliedWare OS How To Note IGMP
Next, look at the output of the command show ip igmp on the Querier
This output now shows two entries, one for each of the following
Page 14 AlliedWare OS How To Note IGMP
When a client leaves a group
Page 15 AlliedWare OS How To Note IGMP
Multiple potential IGMP queriers
Example
Page 16 AlliedWare OS How To Note IGMP
X Configure switch
X Configure switch
X Configure switch
Explanation of Multiple potential IGMP queriers
When there are no group members
Page 18 AlliedWare OS How To Note IGMP
When a client joins a group
Refresh time 228 secs
Page 19 AlliedWare OS How To Note IGMP
Page 20 AlliedWare OS How To Note IGMP
Page 21 AlliedWare OS How To Note IGMP
IGMP proxy
Example
Switch 3 is an IGMP Proxy
X Configure switch
X Configure switch
X Configure switch
Page 23 AlliedWare OS How To Note IGMP
Explanation of IGMP proxy
When there are no group members
When a client joins a group
Refresh time 243 secs
Page 24 AlliedWare OS How To Note IGMP
Page 25 AlliedWare OS How To Note IGMP
When a client leaves a group
How query solicitation works
Query solicitation rapid recovery from topology changes
QS and sends
Initial state
TC and sends
Query Solicit QS
X Configure switch
Why convergence takes so long without query solicitation
Example
X Configure switch
Explanation from the perspective of switch 2, the snooper
Page 30 AlliedWare OS How To Note IGMP
When link comes up again
shows this entry
Explanation from the perspective of switch 1, the querier
again forwarding the multicast stream out the port
Speeding up IGMP convergence in a non-looped topology
Enabling query solicitation on multiple switches in a looped topology
Switch 1 sends GQ
from switch
Switch 2 sends QS
to switch
Example
IGMP filtering controlling multicast distribution
types command
X Configure switch
X Configure switch
X Configure switch
Page 37 AlliedWare OS How To Note IGMP
Dropped
Explanation of IGMP filtering controlling multicast distribution
Received
Passed
Page 39 AlliedWare OS How To Note IGMP
Example
IGMP throttling limiting the number of streams for each subscriber
X Configure switch
X Configure switch
Page 41 AlliedWare OS How To Note IGMP
Page 42 AlliedWare OS How To Note IGMP
X Configure switch
Consider switch 2 after a client on port 2 has joined six groups from
Page 44 AlliedWare OS How To Note IGMP
Note that the group list is sorted by refresh time, not group address
X Modify switch 2 Configuration
When we deny groups instead of replacing them
Page 47 AlliedWare OS How To Note IGMP
Page 48 AlliedWare OS How To Note IGMP
Static IGMP
Example
Switch 2 is an IGMP Snooper
X Configure switch
X Configure switch
z enable IGMP z enable the interface as an IGMP interface
Page 50 AlliedWare OS How To Note IGMP
X Configure switch
Page 51 AlliedWare OS How To Note IGMP
Explanation of Static IGMP
X Modify switch 3 Configuration
When we add a static entry on another switch
Page 53 AlliedWare OS How To Note IGMP
Page 54 AlliedWare OS How To Note IGMP
X Modify switch 3 Configuration
port=5,26 counter
Page 55 AlliedWare OS How To Note IGMP
MulticastPkts
Page 56 AlliedWare OS How To Note IGMP
MulticastPkts
36350
Page 57 AlliedWare OS How To Note IGMP
When a static entry’s port goes down
Querier timer values
How clients leave groups queries and timers
Overview of leave process
Snooper timer values
Consequences for high-loss and high-lag networks
Comparing the Querier and Snooper timers
set igmpsnooping vlan=vlanx fastleave=onoff
IGMP fast leave
Example
set igmpsnooping fastleave=onoff interface=vlanx
Page 62 AlliedWare OS How To Note IGMP
X Configure switch
X Configure switch
X Configure switch
Page 63 AlliedWare OS How To Note IGMP
Explanation of IGMP fast leave
Page 64 AlliedWare OS How To Note IGMP
When fast leave is disabled
It is safe to ignore the group entry on switch
When you enable fast leave on switch
Similarly, we can easily disable Fast Leave on all interfaces
When you set fast leave on all interfaces
Multiple host mode for fast leave
Page 68 AlliedWare OS How To Note IGMP
z Initial configuration on page z Default values on page
Configurable IGMP timers and counters
Timer and counter relationships
z Timer and counter relationships on page z Software versions on page
Software versions
Initial configuration
Configurable IGMP timers and counters Initial configuration
X Configure switch
X Configure switch
X Configure switch
Last Member Query Count and Last Member Query Interval
Default values
What these counters do
1/10secs
Potential problems with changing these counters
How to change these counters
Last Member Query Interval
Last Member Query Count
Page 74 AlliedWare OS How To Note IGMP
What this counter does
Potential problems with changing this counter
How to change this counter
Robustness Variable
How to change this timer
Default Query Interval
What this timer does
Potential problems with changing this timer
How to change this timer
Query Response Interval
What this timer does
Potential problems with changing this timer
Potential problems with changing this timer
Default Timeout Interval
Synchronisation of timers
What this timer does
Next, change the Default Query Interval to 130 seconds
Increase Default Query Interval
Defaults First, the following output shows the default settings
The Default Timeout Interval = 2*125 + 100/10 = 260 seconds
Page 80 AlliedWare OS How To Note IGMP
Increase Query Response Interval
Page 81 AlliedWare OS How To Note IGMP
Override Default Timeout Interval
Default Timeout Interval = 2 * 200 + 10 = 410 seconds
Default Timeout Interval =
Page 82 AlliedWare OS How To Note IGMP
set ip igmp timeout=126
Example of bad choices for timer values
Timer
Default Timeout Interval
Problem 2 Query Response Interval short
Problem 1 Last Member Query Interval too short
Problem 3 Default Timeout Interval too short
not recommend this
For more information, see Synchronisation of timers on page
Example
Stopping snoopers from snooping non-IGMP messages
OSPF
Page 87 AlliedWare OS How To Note IGMP
X Configure switch
X Configure switch
X Configure switch
X Configure the router
Ports 25
Page 89 AlliedWare OS How To Note IGMP
Ports
Disabling All Groups entry for a port
Preventing an All Groups entry for a port
1. Permit port 24 to be an All Groups port again
2. Check the group entry timeout values
3. Reset port 24’s packet counters
Enabling All Groups entry again
Page 92 AlliedWare OS How To Note IGMP
5. Check the group entry timeout values again
8. Check the group entry timeout values again
6. Enable IGMP debugging
Page 93 AlliedWare OS How To Note IGMP
It is most likely that the group entry will time out first
z the ports internal timer hits zero and is refreshed
Page 94 AlliedWare OS How To Note IGMP
z the streams group entry times out and is refreshed, or
This option
Controlling which addresses create All Groups entries
packets from
set igmpsnooping routermode=ip
Configuring switch
delete igmpsnooping routeraddress=224.0.0.5
Page 97 AlliedWare OS How To Note IGMP
Adding other router addresses
Configuring switches 1 and
Page 98 AlliedWare OS How To Note IGMP
To return to the default list, change the router mode to default
Returning to the default list
Page 100 AlliedWare OS How To Note IGMP
Using the other routermode options
2. Check the current IGMP snooping entries
Statically specifying that a port is a router port
Example
4. Stop port 6 from being a static router port
3. Statically add port 6 as a router port attached to VLAN
To remove the static configuration, simply delete it
X A client joins a group
IGMP debugging
Example
X A client leaves a group
X Snooped ports change
X A port entry times out
Page 105 AlliedWare OS How To Note IGMP
X A port in the All Groups list is unplugged
X A report is filtered out
Page 106 AlliedWare OS How To Note IGMP
Page 107 AlliedWare OS How To Note IGMP
X Output for show ip igmp changes
Appendix STP state
Switch
Page 109 AlliedWare OS How To Note IGMP
Switch
USA Headquarters 19800 North Creek Parkway Suite 100 Bothell WA 98011 USA T +1 800 424 4284 F +1 425 481
Switch