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