Allied Telesis AR400 manual Query solicitation rapid recovery from topology changes

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Query solicitation (rapid recovery from topology changes) > How query solicitation works

Query solicitation (rapid recovery from topology changes)

Query Solicitation minimises loss of multicast data after a topology change. It is a built-in feature of Allied Telesis managed layer 3 switches since software versions 281-03 and 2.9.1 when running EPSR or spanning tree (STP, RSTP, or MSTP) for loop protection.

Without Query Solicitation, when the underlying link layer topology changes, multicast data flow can stop for up to several minutes, depending on which port goes down and how much of the timeout period was left (see "Why convergence takes so long without query solicitation" on page 28). Query Solicitation greatly reduces this disruption.

Query Solicitation operates without configuration in networks of Allied Telesis managed layer 3 switches running STP, RSTP, MSTP or EPSR. You may find it helpful to manually enable it in the following other situations:

zloop-free networks running IGMP (see page 33)

znetworks in which not all switches support Query Solicitation (see page 33)

How query solicitation works

Query Solicitation monitors STP, RSTP, MSTP and EPSR messages for topology changes. When it detects a change, it generates a special IGMP Leave message called a Query Solicit. The switch floods the Query Solicit message to all ports in every VLAN that Query Solicitation is enabled on. When the Querier receives the Query Solicit message, it sends out a General Query and waits for clients to respond with Membership Reports. These Reports update the snooping information throughout the network.

Query Solicit messages have a group address of 0.0.0.0.

Query Solicitation works by default (without you enabling it) on all VLANs on the root bridge in an STP instance and on all data VLANs on the master node in an EPSR instance. By default, the root bridge or master node always sends a Query Solicit message when any of the following events occur:

zan STP BPDU packet with the Topology Change (TC) flag arrives at the root bridge

zan STP port on a switch goes from a Discarding to Forwarding state

zthe FDB gets flushed by EPSR

If necessary, you can make clients respond more quickly to the General Query by tuning the IGMP timers, especially the Query Response Interval—see page 77.

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Contents Contents IntroductionConfigurable Igmp timers and counters Query solicitation rapid recovery from topology changesHow clients leave groups queries and timers Example of bad choices for timer valuesProducts and software versions this note applies to Igmp feature Software versions Products 4 AlliedWare OS How To Note IgmpQueriers and Snoopers 5 AlliedWare OS How To Note IgmpIgmp overview 6 AlliedWare OS How To Note Igmp MessagesIP address, binary 7 AlliedWare OS How To Note IgmpChoosing group addresses MAC address, hex8 AlliedWare OS How To Note Igmp Avoid x.0.0.y, x.0.1.y, x.128.0.y, and x.128.1.yExample 9 AlliedWare OS How To Note IgmpIgmp snooping Configure switch 10 AlliedWare OS How To Note Igmp11 AlliedWare OS How To Note Igmp Explanation of Igmp snoopingGroup List Entry timeout 257 Secs Ports All Groups 235 Using Show command output to investigate Igmp stateGroup List Entry timeout 136 secs Ports None 12 AlliedWare OS How To Note Igmp13 AlliedWare OS How To Note Igmp Group Last Adv14 AlliedWare OS How To Note Igmp When a client leaves a groupGroup List Entry timeout 247 secs Ports 15 AlliedWare OS How To Note Igmp Multiple potential Igmp queriers16 AlliedWare OS How To Note Igmp 17 AlliedWare OS How To Note Igmp When there are no group membersOther Querier timeout .. secs All Groups Entry timeout Secs Ports When a client joins a groupGroup List Entry timeout 225 secs Ports 18 AlliedWare OS How To Note IgmpGroup List Last Adv 19 AlliedWare OS How To Note IgmpGroup List 20 AlliedWare OS How To Note Igmp 21 AlliedWare OS How To Note Igmp Igmp proxySwitch 3 is an Igmp Proxy 22 AlliedWare OS How To Note Igmp23 AlliedWare OS How To Note Igmp Group List Entry timeout 122 secs Ports NoneAll Groups Entry timeout 145 Secs Ports Explanation of Igmp proxyGroup Entry timeout Secs Ports 24 AlliedWare OS How To Note IgmpGroup Entry timeout 182 secs Ports 25 AlliedWare OS How To Note IgmpHow query solicitation works Query solicitation rapid recovery from topology changes26 AlliedWare OS How To Note Igmp 27 AlliedWare OS How To Note Igmp Initial stateExample Why convergence takes so long without query solicitation28 AlliedWare OS How To Note Igmp Explanation from the perspective of switch 2, the snooper 29 AlliedWare OS How To Note IgmpAll Groups Entry timeout 236 secs Ports 30 AlliedWare OS How To Note Igmp31 AlliedWare OS How To Note Igmp Explanation from the perspective of switch 1, the querierGroup Entry timeout 18 secs Ports Shows this entryGroup Entry timeout 115 secs Ports 32 AlliedWare OS How To Note Igmp33 AlliedWare OS How To Note Igmp Speeding up Igmp convergence in a non-looped topology34 AlliedWare OS How To Note Igmp Switch 1 sends GQ35 AlliedWare OS How To Note Igmp Igmp filtering controlling multicast distribution36 AlliedWare OS How To Note Igmp Types commandSet switch port=1 igmpfilter=1 Switch 3 is also an Igmp Snooper 37 AlliedWare OS How To Note Igmp38 AlliedWare OS How To Note Igmp Received Passed Dropped39 AlliedWare OS How To Note Igmp No group memberships40 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 46 AlliedWare OS How To Note Igmp When we deny groups instead of replacing themModify switch 2 Configuration Group 224.12.13.11 Entry timeout 255 secs Ports 224.12.13.12 47 AlliedWare OS How To Note Igmp48 AlliedWare OS How To Note Igmp Static IgmpSwitch 2 is an Igmp Snooper 49 AlliedWare OS How To Note Igmp50 AlliedWare OS How To Note Igmp Explanation of Static Igmp Group Entry timeout Infinity Ports51 AlliedWare OS How To Note Igmp 52 AlliedWare OS How To Note Igmp When we add a static entry on another switchModify switch 3 Configuration MulticastPkts 675826All Groups Entry timeout 247 secs Ports 53 AlliedWare OS How To Note Igmp54 AlliedWare OS How To Note Igmp Group Entry timeout Infinity Ports 5,26 55 AlliedWare OS How To Note IgmpMulticastPkts 14756 56 AlliedWare OS How To Note IgmpMulticastPkts 36350 57 AlliedWare OS How To Note Igmp When a static entry’s port goes downGroup Entry timeout Infinity Ports None 58 AlliedWare OS How To Note Igmp How clients leave groups queries and timersQuerier timer values Overview of leave processSnooper timer values 59 AlliedWare OS How To Note IgmpConsequences for high-loss and high-lag networks Comparing the Querier and Snooper timers60 AlliedWare OS How To Note Igmp Describes the new behaviour61 AlliedWare OS How To Note Igmp Igmp fast leaveSwitch 1 is an Igmp Querier 62 AlliedWare OS How To Note Igmp63 AlliedWare OS How To Note Igmp Explanation of Igmp fast leave64 AlliedWare OS How To Note Igmp When fast leave is disabledGroup Entry timeout 2 secs Ports Fast Leave OffGroup Entry timeout Secs Ports None When you enable fast leave on switchIt is safe to ignore the group entry on switch 65 AlliedWare OS How To Note IgmpWhen you set fast leave on all interfaces 66 AlliedWare OS How To Note IgmpTo specify single mode, use either of the commands Multiple host mode for fast leaveTo specify multiple mode, use the command 67 AlliedWare OS How To Note Igmp68 AlliedWare OS How To Note Igmp 69 AlliedWare OS How To Note Igmp Configurable Igmp timers and countersTimer and counter relationships 70 AlliedWare OS How To Note Igmp Initial configurationEach example modifies the following base configuration Software versions71 AlliedWare OS How To Note Igmp Last Member Query Count and Last Member Query Interval Default values72 AlliedWare OS How To Note Igmp What these counters do73 AlliedWare OS How To Note Igmp Potential problems with changing these countersHow to change these counters Last Member Query Interval 255 10secs74 AlliedWare OS How To Note Igmp Last Member Query CountRobustness Variable Potential problems with changing this counterHow to change this counter What this counter doesPotential problems with changing this timer Default Query IntervalWhat this timer does How to change this timerQuery Response Interval 100 10secs 77 AlliedWare OS How To Note IgmpQuery Response Interval 78 AlliedWare OS How To Note Igmp Default Timeout IntervalSynchronisation of timers Default Timeout Interval = 2*130 + 100/10 = 270 seconds 79 AlliedWare OS How To Note Igmp80 AlliedWare OS How To Note Igmp Default Timeout Interval = 2*125 + 100/10 = 260 secondsDefault Timeout Interval 280 Secs Query Response Interval 200 10secsDefault Timeout Interval 180 Secs 81 AlliedWare OS How To Note IgmpDefault Query Interval 200 Secs Default Timeout Interval 410 82 AlliedWare OS How To Note IgmpCommands to configure these settings are Example of bad choices for timer valuesImagine the following changes to the configuration 83 AlliedWare OS How To Note IgmpProblem 3 Default Timeout Interval too short Problem 1 Last Member Query Interval too shortProblem 2 Query Response Interval short Last Member Query Interval was set to 5, using the commandFor more information, see Synchronisation of timers on 85 AlliedWare OS How To Note Igmp86 AlliedWare OS How To Note Igmp Stopping snoopers from snooping non-IGMP messages87 AlliedWare OS How To Note Igmp Router uses Ospf Configure the router88 AlliedWare OS How To Note Igmp Ports 2489 AlliedWare OS How To Note Igmp Ports 25Preventing an All Groups entry for a port Disabled All-groups Ports90 AlliedWare OS How To Note Igmp Disabling All Groups entry for a portEntry timeout 216 Secs Check the group entry timeout valuesReset port 24’s packet counters Enabling All Groups entry again92 AlliedWare OS How To Note Igmp Check the group entry timeout values againEntry timeout Secs MulticastPkts93 AlliedWare OS How To Note Igmp Enable Igmp debuggingEntry timeout 259 Secs 94 AlliedWare OS How To Note Igmp MulticastPkts 91495 AlliedWare OS How To Note Igmp Controlling which addresses create All Groups entries224.0.0.5 Configuring switch96 AlliedWare OS How To Note Igmp 97 AlliedWare OS How To Note Igmp Adding other router addresses Configuring switches 198 AlliedWare OS How To Note Igmp 224.0.0.254 Returning to the default list99 AlliedWare OS How To Note Igmp Using the other routermode options 100 AlliedWare OS How To Note IgmpCheck the current Igmp snooping entries 101 AlliedWare OS How To Note IgmpStatically specifying that a port is a router port Statically add port 6 as a router port attached to Vlan To remove the static configuration, simply delete it102 AlliedWare OS How To Note Igmp Stop port 6 from being a static router portClient joins a group 103 AlliedWare OS How To Note IgmpIgmp debugging Client leaves a group IgmpSnoopMembershipQuery setting timer at 2 secs for group104 AlliedWare OS How To Note Igmp Several minutes later the group entry times outPort entry times out Manager Switch 3 del vlan=100 port=5105 AlliedWare OS How To Note Igmp Snooped ports changePort in the All Groups list is unplugged 106 AlliedWare OS How To Note IgmpReport is filtered out 107 AlliedWare OS How To Note Igmp Output for show ip igmp changesAppendix STP state Switch108 AlliedWare OS How To Note Igmp State Forwarding109 AlliedWare OS How To Note Igmp Manager Switch 3 show stp port=25-26
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