Allied Telesis AR400 manual Potential problems with changing these counters

Page 73

Configurable IGMP timers and counters > Last Member Query Count and Last Member Query Interval

Potential problems with changing these counters

For most networks, the default LMQI and LMQC values work. You should only change them if you are aware of the likely effect on the network. In particular, note that:

zChanging the LMQC automatically changes the Robustness Variable. Therefore, we do not recommend setting the LMQC to 1, because it removes the system’s allowance for packet loss. See page 75 for more information about the consequences of changing the Robustness Variable.

zIf you set the LMQI (or LMQC, or both) too low, clients will not be able to reply to Specific Queries quickly enough and the Querier and Snoopers may delete group entries for ports that still need to receive multicasts. If this happens, some or all clients briefly lose the multicast stream.

The default values of LMQI (10) and LMQC (2) mean that the Querier must receive client Membership Reports within 2 seconds of the first Query. This is already quite a short time and we do not recommend reducing it even more. For example, reducing the LMQI to 5 would allow only 1 second for responses, which may be too little.

How to change these counters

The following example increases LMQI a lot, and then shows the resulting changed refresh time.

Manager Switch 1> set ip igmp lmqi=255

Info (1005003): Operation successful.

Manager Switch 1> show ip igmp

IGMP Protocol

------------------------------------------------------------------------

Status

Enabled

Default Query Interval

125

secs

Default Timeout Interval

260

secs

Last Member Query Interval

255

(1/10secs)

Last Member Query Count

2

 

Robustness Variable

2

 

Query Response Interval

100

(1/10secs)

Disabled All-groups ports

None

 

Interface Name

vlan100

(DR)

 

Group List

 

 

 

Group. 224.12.13.14

Last Adv. 172.31.0.222

Refresh time 49 secs

Ports 49

 

 

 

------------------------------------------------------------------------

The refresh time in seconds is (LMQI/10) * LMQC = 255/10 * 2 = 51 seconds

So with the new LMQI setting of 255 and the default LMQC setting of 2, the IGMP Querier waits 51 seconds for a Membership Report to arrive before it ages out the IGMP entry. Note that the output above displays 49 seconds, because it took us 2 seconds to enter the command show ip igmp.

Page 73 AlliedWare™ OS How To Note: IGMP

Image 73
Contents Introduction ContentsHow clients leave groups queries and timers Query solicitation rapid recovery from topology changesConfigurable Igmp timers and counters Example of bad choices for timer valuesProducts and software versions this note applies to 4 AlliedWare OS How To Note Igmp Igmp feature Software versions ProductsIgmp overview 5 AlliedWare OS How To Note IgmpQueriers and Snoopers Messages 6 AlliedWare OS How To Note IgmpChoosing group addresses 7 AlliedWare OS How To Note IgmpIP address, binary MAC address, hexAvoid x.0.0.y, x.0.1.y, x.128.0.y, and x.128.1.y 8 AlliedWare OS How To Note IgmpIgmp snooping 9 AlliedWare OS How To Note IgmpExample 10 AlliedWare OS How To Note Igmp Configure switchExplanation of Igmp snooping 11 AlliedWare OS How To Note IgmpGroup List Entry timeout 136 secs Ports None Using Show command output to investigate Igmp stateGroup List Entry timeout 257 Secs Ports All Groups 235 12 AlliedWare OS How To Note IgmpGroup Last Adv 13 AlliedWare OS How To Note IgmpGroup List Entry timeout 247 secs Ports When a client leaves a group14 AlliedWare OS How To Note Igmp Multiple potential Igmp queriers 15 AlliedWare OS How To Note Igmp16 AlliedWare OS How To Note Igmp Other Querier timeout .. secs When there are no group members17 AlliedWare OS How To Note Igmp Group List Entry timeout 225 secs Ports When a client joins a groupAll Groups Entry timeout Secs Ports 18 AlliedWare OS How To Note IgmpGroup List 19 AlliedWare OS How To Note IgmpGroup List Last Adv 20 AlliedWare OS How To Note Igmp Igmp proxy 21 AlliedWare OS How To Note Igmp22 AlliedWare OS How To Note Igmp Switch 3 is an Igmp ProxyAll Groups Entry timeout 145 Secs Ports Group List Entry timeout 122 secs Ports None23 AlliedWare OS How To Note Igmp Explanation of Igmp proxy24 AlliedWare OS How To Note Igmp Group Entry timeout Secs Ports25 AlliedWare OS How To Note Igmp Group Entry timeout 182 secs Ports26 AlliedWare OS How To Note Igmp Query solicitation rapid recovery from topology changesHow query solicitation works Initial state 27 AlliedWare OS How To Note Igmp28 AlliedWare OS How To Note Igmp Why convergence takes so long without query solicitationExample 29 AlliedWare OS How To Note Igmp Explanation from the perspective of switch 2, the snooper30 AlliedWare OS How To Note Igmp All Groups Entry timeout 236 secs PortsGroup Entry timeout 18 secs Ports Explanation from the perspective of switch 1, the querier31 AlliedWare OS How To Note Igmp Shows this entry32 AlliedWare OS How To Note Igmp Group Entry timeout 115 secs PortsSpeeding up Igmp convergence in a non-looped topology 33 AlliedWare OS How To Note IgmpSwitch 1 sends GQ 34 AlliedWare OS How To Note IgmpIgmp filtering controlling multicast distribution 35 AlliedWare OS How To Note IgmpSet switch port=1 igmpfilter=1 Types command36 AlliedWare OS How To Note Igmp 37 AlliedWare OS How To Note Igmp Switch 3 is also an Igmp SnooperReceived Passed Dropped 38 AlliedWare OS How To Note IgmpNo group memberships 39 AlliedWare OS How To Note Igmp40 AlliedWare OS How To Note Igmp 41 AlliedWare OS How To Note Igmp 42 AlliedWare OS How To Note Igmp 43 AlliedWare OS How To Note Igmp 44 AlliedWare OS How To Note Igmp 45 AlliedWare OS How To Note Igmp Modify switch 2 Configuration When we deny groups instead of replacing them46 AlliedWare OS How To Note Igmp 47 AlliedWare OS How To Note Igmp Group 224.12.13.11 Entry timeout 255 secs Ports 224.12.13.12Static Igmp 48 AlliedWare OS How To Note Igmp49 AlliedWare OS How To Note Igmp Switch 2 is an Igmp Snooper50 AlliedWare OS How To Note Igmp 51 AlliedWare OS How To Note Igmp Group Entry timeout Infinity PortsExplanation of Static Igmp Modify switch 3 Configuration When we add a static entry on another switch52 AlliedWare OS How To Note Igmp MulticastPkts 67582653 AlliedWare OS How To Note Igmp All Groups Entry timeout 247 secs Ports54 AlliedWare OS How To Note Igmp 55 AlliedWare OS How To Note Igmp Group Entry timeout Infinity Ports 5,26MulticastPkts 36350 56 AlliedWare OS How To Note IgmpMulticastPkts 14756 Group Entry timeout Infinity Ports None When a static entry’s port goes down57 AlliedWare OS How To Note Igmp Querier timer values How clients leave groups queries and timers58 AlliedWare OS How To Note Igmp Overview of leave process59 AlliedWare OS How To Note Igmp Snooper timer values60 AlliedWare OS How To Note Igmp Comparing the Querier and Snooper timersConsequences for high-loss and high-lag networks Describes the new behaviourIgmp fast leave 61 AlliedWare OS How To Note Igmp62 AlliedWare OS How To Note Igmp Switch 1 is an Igmp QuerierExplanation of Igmp fast leave 63 AlliedWare OS How To Note IgmpGroup Entry timeout 2 secs Ports When fast leave is disabled64 AlliedWare OS How To Note Igmp Fast Leave OffIt is safe to ignore the group entry on switch When you enable fast leave on switchGroup Entry timeout Secs Ports None 65 AlliedWare OS How To Note Igmp66 AlliedWare OS How To Note Igmp When you set fast leave on all interfacesTo specify multiple mode, use the command Multiple host mode for fast leaveTo specify single mode, use either of the commands 67 AlliedWare OS How To Note Igmp68 AlliedWare OS How To Note Igmp Timer and counter relationships Configurable Igmp timers and counters69 AlliedWare OS How To Note Igmp Each example modifies the following base configuration Initial configuration70 AlliedWare OS How To Note Igmp Software versions71 AlliedWare OS How To Note Igmp 72 AlliedWare OS How To Note Igmp Default valuesLast Member Query Count and Last Member Query Interval What these counters doHow to change these counters Potential problems with changing these counters73 AlliedWare OS How To Note Igmp Last Member Query Interval 255 10secsLast Member Query Count 74 AlliedWare OS How To Note IgmpHow to change this counter Potential problems with changing this counterRobustness Variable What this counter doesWhat this timer does Default Query IntervalPotential problems with changing this timer How to change this timerQuery Response Interval 77 AlliedWare OS How To Note IgmpQuery Response Interval 100 10secs Synchronisation of timers Default Timeout Interval78 AlliedWare OS How To Note Igmp 79 AlliedWare OS How To Note Igmp Default Timeout Interval = 2*130 + 100/10 = 270 secondsDefault Timeout Interval 280 Secs Default Timeout Interval = 2*125 + 100/10 = 260 seconds80 AlliedWare OS How To Note Igmp Query Response Interval 200 10secs81 AlliedWare OS How To Note Igmp Default Timeout Interval 180 Secs82 AlliedWare OS How To Note Igmp Default Query Interval 200 Secs Default Timeout Interval 410Imagine the following changes to the configuration Example of bad choices for timer valuesCommands to configure these settings are 83 AlliedWare OS How To Note IgmpProblem 2 Query Response Interval short Problem 1 Last Member Query Interval too shortProblem 3 Default Timeout Interval too short Last Member Query Interval was set to 5, using the command85 AlliedWare OS How To Note Igmp For more information, see Synchronisation of timers onStopping snoopers from snooping non-IGMP messages 86 AlliedWare OS How To Note Igmp87 AlliedWare OS How To Note Igmp 88 AlliedWare OS How To Note Igmp Configure the routerRouter uses Ospf Ports 24Ports 25 89 AlliedWare OS How To Note Igmp90 AlliedWare OS How To Note Igmp Disabled All-groups PortsPreventing an All Groups entry for a port Disabling All Groups entry for a portReset port 24’s packet counters Check the group entry timeout valuesEntry timeout 216 Secs Enabling All Groups entry againEntry timeout Secs Check the group entry timeout values again92 AlliedWare OS How To Note Igmp MulticastPktsEntry timeout 259 Secs Enable Igmp debugging93 AlliedWare OS How To Note Igmp MulticastPkts 914 94 AlliedWare OS How To Note IgmpControlling which addresses create All Groups entries 95 AlliedWare OS How To Note Igmp96 AlliedWare OS How To Note Igmp Configuring switch224.0.0.5 97 AlliedWare OS How To Note Igmp 98 AlliedWare OS How To Note Igmp Configuring switches 1Adding other router addresses 99 AlliedWare OS How To Note Igmp Returning to the default list224.0.0.254 100 AlliedWare OS How To Note Igmp Using the other routermode optionsStatically specifying that a port is a router port 101 AlliedWare OS How To Note IgmpCheck the current Igmp snooping entries 102 AlliedWare OS How To Note Igmp To remove the static configuration, simply delete itStatically add port 6 as a router port attached to Vlan Stop port 6 from being a static router portIgmp debugging 103 AlliedWare OS How To Note IgmpClient joins a group 104 AlliedWare OS How To Note Igmp IgmpSnoopMembershipQuery setting timer at 2 secs for groupClient leaves a group Several minutes later the group entry times out105 AlliedWare OS How To Note Igmp Manager Switch 3 del vlan=100 port=5Port entry times out Snooped ports changeReport is filtered out 106 AlliedWare OS How To Note IgmpPort in the All Groups list is unplugged Output for show ip igmp changes 107 AlliedWare OS How To Note Igmp108 AlliedWare OS How To Note Igmp SwitchAppendix STP state State Forwarding109 AlliedWare OS How To Note Igmp Manager Switch 3 show stp port=25-26