Allied Telesis AR400 manuale d’uso

C613-16087-00 REV C www .alliedtelesis.com AlliedW ar e™ OS How T o | Intr oduction Allied T elesis r outers and managed lay er 3 sw itches use IGMP—Internet Group Management Pr otocol— to track which multicast gr oups their cl ients belong to. This enables them to send the corr ect multimedia streams to the corr ect destination. This How T o[...]

Page 2 | AlliedW are™ OS How T o Note: IGMP Intro duction > Contents Multiple potential IGMP queriers ................................................................................ .............. ........ 15 Example ................................................. ................................................. ..................... .....[...]

Page 3 | AlliedW are™ OS How T o Note: IGMP Intr oduction > Pr oducts and software v ersions this note applies to Stopping snoopers fr o m snooping no n-IGMP messages .......... ....................................... ............. 86 Example ................................................. ................................................. ..[...]

Page 4 | AlliedW are™ OS How T o Note: IGMP Intr oduction > Pr oducts and software v ersions this note applies to The following table sho ws the software versions and pr oducts each feature is a vai lable on. For most examples in this How T o Note, we used: z one A T -8948 switch, with Softwar e V ersion 2.7.6 z two Ra pier 24i switches, with [...]

Page 5 | AlliedW are™ OS How T o Note: IGMP IGMP ov er view > Querie rs and Snoopers IGMP o v er vie w Clients in an IP subnetwork use IGMP to indicate that they ar e interested in receiving a multicast. IGMP then ensures that r outers and switches forward m ulticast packets out the a ppropriate ports to the interested clients. IGMP is v er y [...]

Page 6 | AlliedW are™ OS How T o Note: IGMP IGMP ov er view > Messages The k ey differ ences between a net work’ s Querier and its Snoopers are: z The Querier generates Query me ssages to find out which por ts need to transmit each multicast str eam. The Snoopers also use Quer y me ssages to find this ou t, but they use the Querier’ s mess[...]

Page 7 | AlliedW are™ OS How T o Note: IGMP IGMP ov er view > Choosing group ad dresses Choosing gr oup addr esses This section describes things you need to be a ware of when choosing ad dresses for y our multicast gr oups. Reser ved IP addr esses IP addr esses in the ran ge 224.0.0.0-239.255.255.25 5 are mu lticast addr esses, but many addr e[...]

Page 8 | AlliedW are™ OS How T o Note: IGMP IGMP ov er view > Choosing group ad dresses A void x.0.0.y , x.0. 1 .y , x. 1 28.0.y , and x. 1 28. 1 .y It is par ticularly important to av oid using any addr ess in the ranges x.0.0.y , x. 1 28.0.y , x.0. 1 .y , or x. 1 28. 1 .y (where x is 224-239 and y is 1 -254). This is because x. 0.0.y and x. [...]

Page 9 | AlliedW are™ OS How T o Note: IGMP IGMP snooping > Example IGMP snooping In this example , we discuss IGMP snooping, the ke y to efficient multicast traffic flow in a la yer 2 netw ork. IGMP snooping is enabled by default on switch ports in Allied T elesis managed la yer 3 s witches and routers—it does not r equire an y configuratio[...]

Page 10 | AlliedW are™ OS How T o Note: IGMP IGMP snooping > Example Switch 1 is configured with IGMP , which mak es it the IGMP Querier in this network. It is best practice to mak e the Querier the closest switch to the multicast source, and in this example swi tc h 1 is closest. For mor e information about queriers see "Multiple potenti[...]

Page 11 | AlliedW are™ OS How T o Note: IGMP IGMP snooping > Explanatio n of IGMP snooping Explanation of IGMP snooping This section steps thr ough the events that occu r in a typical use of multicasting in this network: to str eam multicast pack ets for a gr oup. IGMP learning process The following figur e shows the pr ocess by whic h IGMP tr[...]

Page 12 | AlliedW are™ OS How T o Note: IGMP IGMP snooping > Explanatio n of IGMP snooping Using Sho w command output to in vestigate IGMP state No gr oup members In the first stage of the figure abo ve, the multic ast ser ver is turned on and is streaming gr oup 224. 1 2. 1 3. 1 4 to the Querier , switch 1 . Switch 1 knows abou t the group , [...]

Page 13 | AlliedW are™ OS How T o Note: IGMP IGMP snooping > Explanatio n of IGMP snooping This output now shows tw o entries, one for each of the follo wing: z gr oup 224.12.13.14 and port 3, which shows that the client is attached to the Snooper through port 3 and is listeni ng to group 224.12.13.14. The Snooper created this entr y at stage [...]

Page 14 | AlliedW are™ OS How T o Note: IGMP IGMP snooping > Explanatio n of IGMP snooping Finally , loo k at the output of the command sho w igmpsnooping on th e Querier . Ev en though switch 1 is the Querier for this netw ork inst ead of a Snooper , th is command shows that a client for gr oup 224. 1 2. 1 3. 1 4 is r eached out por t 49. Whe[...]

Page 15 | AlliedW are™ OS How T o Note: IGMP Multiple potential IGMP queriers > Example Multiple potential IGMP queriers T o find out more about IGMP , w e next inv estigate what happens when mor e than one router or switch has an IGMP configuration. RFC 2236, Internet Gr oup Management Protocol, V ersion 2, sa ys that each La ye r 2 network s[...]

Page 16 | AlliedW are™ OS How T o Note: IGMP Multiple potential IGMP queriers > Example Switch 1 is a potential IGMP Querier . It acts as a Snooper if it is not elected as the Querier . Switch 2 is also a potential IGMP Querier . It acts as a Snooper if not elected as the Querier . Switch 3 is an IGMP Snooper . It forwards m ulticast pac k ets[...]

Page 17 | AlliedW are™ OS How T o Note: IGMP Multiple potential IGMP queriers > Explanation of Multiple potential IGMP queriers Explanation of Multiple potential IGMP queriers When ther e are no gr oup members Switch 1 and switch 2 are both possible Queriers, and an election determines which switch becomes the actual Querier . W e can see the [...]

Page 18 | AlliedW are™ OS How T o Note: IGMP Multiple potential IGMP queriers > Explanation of Multiple potential IGMP queriers When a client joins a gr oup Now imagine that Client 1 sends a Membership Repor t to switch 2 for the gr oup 224. 1 2. 1 3. 1 4. If we check the group member ship for switch 2 b y using the command sho w igmpsnoopi ng[...]

Page 19 | AlliedW are™ OS How T o Note: IGMP Multiple potential IGMP queriers > Explanation of Multiple potential IGMP queriers T o see the differ ence between a s witch acting as a Snooper and a switch acting as a Queri er , compare the IGMP snooping table for switch 1 (abov e) with its IGMP table (below). They seem to contradict each other .[...]

Page 20 | AlliedW are™ OS How T o Note: IGMP Multiple potential IGMP queriers > Explanation of Multiple potential IGMP queriers Also , note that (DR) appears in the output of sho w ip ig mp on switch 2. This tells y ou that switch 2 is the Designated Rout er (the IGMP Querier) f or vlan 1 00. Manager Switch 2> show igmpsnoopin g IGMP Snoopi[...]

Page 21 | AlliedW are™ OS How T o Note: IGMP IGMP pr oxy > Example IGMP pr o xy In v er y simple tr ee-design networks, IGMP Pr oxy is a useful simple alte rnative to a multicast r outing protocol for multicasting betw een VLANs. An IGMP Pr oxy sends IGMP Me mbership Repor t and Lea ve gr oup messages to an upstream subnetwork on behalf of do [...]

Page 22 | AlliedW are™ OS How T o Note: IGMP IGMP pr oxy > Example Switch 1 —the closest switch to the mult icast sour ce—is an IGMP Querier . Switch 2 is an IGMP Snooper . IGMP snooping is enabled by default and does not need any configuration. Switch 3 is an IGMP Pr oxy . X Configur e switch 1 set system name="Switch 1" # Switc[...]

Page 23 | AlliedW are™ OS How T o Note: IGMP IGMP pr oxy > Explanation of IGMP pr oxy Explanation of IGMP pr o xy When ther e are no gr oup members The multicast ser ver str eams group 224. 1 2. 1 3. 1 4 to switch 1 thr ough port 1 . IGMP snooping detects the stream, as you can see by using the command sho w igmpsnooping on s witch 1 . When a [...]

Page 24 | AlliedW are™ OS How T o Note: IGMP IGMP pr oxy > Explanation of IGMP pr oxy thr ough vlan200. Output of the commands sho w ip igmp and sho w igmpsnooping sh ow that switch 3 knows of a client inter ested in the group 224. 1 2. 1 3. 1 4 through port 25. Manager Switch 3> show ip igmp IGMP Protocol -------------------------- -------[...]

Page 25 | AlliedW are™ OS How T o Note: IGMP IGMP pr oxy > Explanation of IGMP pr oxy Switch 1 receiv es the pro xied report from s witch 3. Switch 1 notes that switch 3 is interested in the group 224. 1 2. 1 3. 1 4 and sends the gr oup mult icast to switch 3 on port 49. Output of the command show igmpsnooping shows the members hip that switch[...]

Page 26 | AlliedW are™ OS How T o Note: IGMP Query solicitation (rapid r ecovery fro m topology changes) > How quer y solicitation w orks Quer y solicitation (rapid r eco v er y from topolo g y chang es) Quer y Solicitation minimises loss of multicast data after a topology change . It is a built-in featur e of Allied T elesis managed la yer 3 [...]

Page 27 | AlliedW are™ OS How T o Note: IGMP Query solicitation (rapid r ecovery fro m topology changes) > How quer y solicitation w orks The following figur e shows how Quer y Solicitation works when a port goes down. TC 1. Link to Switch 4 goes down. Switch 3 stops blocking and sends topology change (TC) Switch 3 Switch 2: STP root QS QS 2. [...]

Page 28 | AlliedW are™ OS How T o Note: IGMP Quer y solicitation (ra pid recov er y fr om topolog y changes) > Why c onvergence tak es so long wi thout quer y solicitation Wh y conv ergence tak es so long without quer y solicitation This section illustrates IGMP conv ergence in a sim ple netw ork that does not need STP because it has no switch[...]

Page 29 | AlliedW are™ OS How T o Note: IGMP Quer y solicitation (ra pid recov er y fr om topolog y changes) > Why c onvergence tak es so long wi thout quer y solicitation Explanation fr om th e perspective of s witch 2, the snooper When link is up When the link is connected (all por ts are up ), the Snooper has entries f or two por ts: z port[...]

Page 30 | AlliedW are™ OS How T o Note: IGMP Quer y solicitation (ra pid recov er y fr om topolog y changes) > Why c onvergence tak es so long wi thout quer y solicitation When link comes up agai n When we r eco nnect por t 1 on the Snooper , the All Groups entry does not rea pp e a r . Eventuall y , the Querier sends an IGMP Quer y , which th[...]

Page 31 | AlliedW are™ OS How T o Note: IGMP Quer y solicitation (ra pid recov er y fr om topolog y changes) > Why c onvergence tak es so long wi thout quer y solicitation Explanation fr om the perspective of switch 1 , the querier When link is up When the link is connected (all por ts are up), the Querier has an entr y for por t 1 , so it sen[...]

Page 32 | AlliedW are™ OS How T o Note: IGMP Quer y solicitation (ra pid recov er y fr om topolog y changes) > Why c onvergence tak es so long wi thout quer y solicitation When link comes up agai n When we r eco nnect por t 1 on the Snooper , the por t do es not reappe ar because the Querier has not y et receiv ed a Repor t over it. Ther efor [...]

Page 33 | AlliedW are™ OS How T o Note: IGMP Query solicitation (rapid r ecovery from topol og y changes) > Speeding up IGMP con vergence in a n on-looped topology Speeding up IGMP con v ergence in a non-looped topolo g y The pr evious section describ ed how it can tak e up to 1 25 seconds for multicasting to r ecov er in a non-looped topology[...]

Page 34 | AlliedW are™ OS How T o Note: IGMP Query solicitation (rapid r ecovery from to polog y changes) > Enabling query solicitation on m ultiple switches in a looped to pology So one topolog y change caused three Query Solicits, three Genera l Queries, and thr ee Repor ts. Switch 1: Querier Switch 3 Switch 2: STP root Initial state: Port o[...]

Page 35 | AlliedW are™ OS How T o Note: IGMP IGMP filtering (contr olling multicast di stribution) > Example IGMP filtering (contr olli ng multicast distribution) IGMP filtering lets you contr ol the distribution of multicast ser vices on each switch por t. Filtering is useful for subscripti on ser vices wh en clients must be explicitly author[...]

Page 36 | AlliedW are™ OS How T o Note: IGMP IGMP filtering (contr olling multicast di stribution) > Example Switch 1 —the closest switch to the m ulticast sour ce—is an IGMP Querier . The filter is configured on it, as sho wn in bold in the script below . Note that the or der of entries in a filter is impor tant. When IGMP tries to match [...]

Page 37 | AlliedW are™ OS How T o Note: IGMP IGMP filtering (contr olling multicast di stribution) > Example Switch 2 is an IGMP Snooper . IGMP snooping is enabled by default and does not need any configuration. Switch 3 is also an IGMP Snooper . X Configur e switch 2 set system name="Switch 2" # STP general configuratio n enable stp[...]

Page 38 | AlliedW are™ OS How T o Note: IGMP IGMP filtering (contr olling multicast distribution) > Explanation of IGMP filtering (contr olling multi cast distribution) Explanation of IGMP filtering (contr olling multicast distribution) Immediately after ap plying the filter , we check the gr oup entries on switch 1 by us ing the command sho w[...]

Page 39 | AlliedW are™ OS How T o Note: IGMP IGMP filtering (contr olling multicast distribution) > Explanation of IGMP filtering (contr olling multi cast distribution) If we enter these commands again a fe w minutes later , we see that the filter has dr opped pack ets and the group entry has expired and disappear ed. Manager Switch 1> show[...]

Page 40 | AlliedW are™ OS How T o Note: IGMP IGMP thr ottling (limiting the number o f streams for each subscriber) > Example IGMP thr ottling (limiting the number of str eams for each subscriber) IGMP thr ottling allows y ou to limit the number of streams that subscribers ma y a ccess at a giv en time , for example, to protect fr om bandwidth[...]

Page 41 | AlliedW are™ OS How T o Note: IGMP IGMP thr ottling (limiting the number o f streams for each subscriber) > Example Switch 1 is an IGMP Querier . Note that it has a filter configured o n it, which is fr om the pr evious example. Switch 2 is an IGMP Snooper . IGMP snooping is enabled by default and does not need any configuration. Swi[...]

Page 42 | AlliedW are™ OS How T o Note: IGMP IGMP thr ottling (limiting the number o f streams for each subscriber) > Example Switch 3 is also an IGMP Snooper . X Configur e switch 3 set system name="Switch 3" # STP general configuratio n enable stp=default set stp=default mode=rapid set stp port=3 edgeport=ye s # VLAN general config[...]

Page 43 | AlliedW are™ OS How T o Note: IGMP IGMP thro ttling (limiting the number of streams for each subscrib er) > Explanation of IGMP throttling (limiting the n umber of streams Explanation of IGMP thr ottling (limiting the number of streams f or each subscriber) In this example , switch 2’ s configurati on limits port 2 to six concurren[...]

Page 44 | AlliedW are™ OS How T o Note: IGMP IGMP thro ttling (limiting the number of streams for each subscrib er) > Explanation of IGMP throttling (limiting the n umber of streams Next, the client joins three mor e gr oups (224. 1 2. 1 3. 1 7-224. 1 2. 1 3. 1 9). Output fr om the command sho w igmpsnooping still shows six memberships, but th[...]

Page 45 | AlliedW are™ OS How T o Note: IGMP IGMP thro ttling (limiting the number of streams for each subscrib er) > Explanation of IGMP throttling (limiting the n umber of streams When switch 2 dr ops groups b y throttling, it does not send a Lea ve message, because IGMP snooping cannot generate IGMP packet s. Ther efore, the Querier (switch[...]

Page 46 | AlliedW are™ OS How T o Note: IGMP IGMP thro ttling (limiting the number of streams for each subscrib er) > Explanation of IGMP throttling (limiting the n umber of streams Membership Report for that group . IGMP th r ottling cannot distinguish between differ ent clients on the same por t. For this r eason, the limit is tied to the po[...]

Page 47 | AlliedW are™ OS How T o Note: IGMP IGMP thro ttling (limiting the number of streams for each subscrib er) > Explanation of IGMP throttling (limiting the n umber of streams gr oup. The following output for the command show igmpsnooping demonstrates this. Note that the timeout for the gr oups 224. 1 2. 1 3. 11 and 224. 1 2. 1 3. 1 2 ha[...]

Page 48 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Example Static IGMP Static IGMP enables you to configur e a switch with specified gr oup-to-interface or group-to- port mapp ings, which you ma y want to do if: z your netw ork includes hosts that ca nnot send IGMP Membership Repor ts z you need to guarantee that a specific multicast s[...]

Page 49 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Example Switch 1 is an IGMP Querier and has the static IGMP ent r y . S ta tic I GMP al so req uires you t o: z add an IP addr ess to the interface to which you will attach the static entry z enable IGMP z enable the interface as an IGMP interface Switch 2 is an IGMP Snooper . X Config[...]

Page 50 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Example Switch 3 is also an IGMP Snooper . Later in this example , we will add a static IGMP entry on this switch. "Modify sw itch 3 Configuration" on page 52 sho ws the extra com mands for this. X Configur e switch 3 set system name="Switch 3" # STP general configu[...]

Page 51 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Explanati on of Static IGMP Explanation of Static IGMP When the IGMP static en tr y is created on switch 1 , entries immediately a ppear in the IGMP snooping table and the IGMP table . Manager Switch 1> show igmpsnoopin g IGMP Snooping -------------------------- --------------------[...]

Page 52 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Explanati on of Static IGMP When the gr oup 22 4. 1 2. 1 3. 1 4 starts streaming into s witch 1 , we can use the command sho w swi tch po r t =5 co un te r to watch the number of multicast p ackets sent on por t 5 incr ease . This means that the link is up and the static IGMP entr y is[...]

Page 53 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Explanati on of Static IGMP T o see the effect that the ne w configuration has on switch 1 , we can check the IGMP snooping and IGMP tables . The IGMP snooping table shows that s witch 1 now has an All Gr oups entr y because it is no longer the Quer ier . The IGMP table also shows that[...]

Page 54 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Explanati on of Static IGMP W e can see the static entr y on switch 3 by checking the IGMP snoo ping and IGMP tables. Note that switch 3—the Querier—has no entry for port 26 and therefor e does not send the multicast to switch 1 . This is because the static entry joined switch 1 to[...]

Page 55 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Explanati on of Static IGMP T o see the new static entry , we use the commands show igmp snooping and sho w ip igmp , and to see m ulticast packets str eaming, we use the command sho w swit ch port=5,26 counter . X Modify switch 3 Configuration destroy ip igmp destinatio n=224.12.13.14[...]

Page 56 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Explanati on of Static IGMP Manager Switch 3> show sw i tch port=5,26 counter Switch Port Counters --------------------------------- ----------------------------------------- Port 5. Fast Ethernet MAC counter s: Combined receive/transmit packet s by size (octets) counters: 64 3027 5[...]

Page 57 | AlliedW are™ OS How T o Note: IGMP Static IGMP > Explanati on of Static IGMP When a static entr y’ s port goes do wn Finally , note that when the por t attached to a static entr y goes down, the static entr y remains but no ports are attached to it. Y ou can se e this fr om the output of the commands sho w igmpsnoopi ng and sho w i[...]

Page 58 | AlliedW are™ OS How T o Note: IGMP How clients leav e groups : queries and timers > Ov er view of leav e process Ho w clients lea v e gr oups: queries and timers When a client lea ves a gr oup, the Snoopers and the Querier check which por ts now ha v e clients that belong to that gr oup. The y will st op forwarding the gr oup’ s tr[...]

Page 59 | AlliedW are™ OS How T o Note: IGMP How clients lea ve grou ps: queries and timers > Snooper timer values The command sho w ip igmp displa ys the timer for the most r ecently updated por t as the gr oup’ s Refresh Time . From Software V ersion 29 1 -08, the command sho w igmpsnoopi ng vlan={ < vid >|all} detail displays the ti[...]

Page 60 | AlliedW are™ OS How T o Note: IGMP How clients lea ve groups: queries and tim ers > Comparing the Querier and Snooper timers z T o calculate the timer , the Snooper tak es the LMQI value that it r eceives fr om the Querier and multiplies it by the Snooper’ s own LMQC . z The Snooper only r educes the timer if it receiv es a Lea v e[...]

Page 61 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Example IGMP fast lea ve IGMP Fast Lea ve enhances y o ur control over r outer or switch bandwidth. Enabling Fast Leav e tells IGMP snooping to stop the tr ansmission of a gr oup multicast stream to a port as soon as it r eceives a Lea ve message on that port. No timeouts are obse[...]

Page 62 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Example Switch 1 is an IGMP Querier . Switch 2 is an IGMP Snooper . IGMP snooping is enabled by default and does not need any configuration. Switch 3 is also an IGMP Snooper . Fast lea ve is enabled on this switch. X Configur e switch 1 set system name="Switch 1" # STP g[...]

Page 63 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Explanation of IGMP fast lea ve Explanation of IGMP fast lea v e Imagine that client 2 on sw itch 3 sends a Membership Report to join the grou p 224. 1 2. 1 3. 1 4. The Snooper , switch 3, adds this to its the IGMP snooping table . When the same client then sends a Lea ve message,[...]

Page 64 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Explanation of IGMP fast lea ve When fast lea ve is disabled The IGMP Snooper sees the Me mbership Quer y from the Quer ier and accor ding ly sets its expir y time to match the Querier . Output of the command sho w igmpsnooping on switch 3 shows that the timeout for the gr o up 22[...]

Page 65 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Explanation of IGMP fast lea ve When y ou enable fast lea ve on switch 3 When Fast Lea v e is enabled on switch 3, but not on switch 1 , an interesting chain of e vents occurs when the client sends a Lea ve me ssage, as shown in the following diagram. The result of this is that s [...]

Page 66 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Explanation of IGMP fast lea ve When y ou set fast le a ve on all interfaces Fast lea ve is enabled on a per -interface basis, but if you do not specify an interface, it is enabled on all interfaces. In this example , th at means that if no VLAN is specified when enabling Fast Lea[...]

Page 67 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Explanation of IGMP fast lea ve Multiple host mode for f ast lea ve The pr evious discussion assu mes that only one c lient is attached to the port on the Snooper . Imagine instead a situation where m ultiple clie nts are attached to a single port on the snooping switch, as the fo[...]

Page 68 | AlliedW are™ OS How T o Note: IGMP IGMP fast lea ve > Explanation of IGMP fast lea ve Y ou can see the list of hosts for e ach por t by entering the command show igmpsnooping and specifying the detai l parameter : show igmpsnooping vlan={ name |1..4094|all} [group={ multicast-ip-address |allgroups}] detail The group parameter lets yo[...]

Page 69 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Timer and counter relationships Configurable IGMP timers and counters This section looks at some of the timers an d counters that contr o l how often IGMP sends queries and how quickl y entries time out. First, it gives b ackgr ound information in the followin[...]

Page 70 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Softwa re vers ions Softwar e versions Since softwar e versions 28 1 -03 and 2.9. 1 , IGMP automatically sets the Default Timeout Inter val to the value from the form ula in the section above. Therefor e , if y ou cha nge any of the Robustness V ariable , the [...]

Page 71 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and coun ters > Initial configuration Switch 1 is an IGMP Querier . Switch 2 is an IGMP Snooper . Switch 3 is also an IGMP Snooper . X Configur e switch 1 set system name="Switch 1" # STP general configuratio n enable stp=default set stp=default mode=rapid set stp=[...]

Page 72 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and co unters > Default values Default values Output of the command sho w ip igmp sho ws the values of the co nfigurable IGMP settings. The following output sh ows the default values. Note that units for Last Member Query Inter val (LMQI) and Quer y Response Inter val are 0.[...]

Page 73 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > L ast Member Quer y Count and Last Member Qu er y Inter val P otential pr oblems with changing these counters For most netw orks, the default LMQI and LMQC values work. Y ou should only change them if you ar e awar e of the likely effect on the netw ork. In pa[...]

Page 74 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > L ast Member Quer y Count and Last Member Qu er y Inter val Similarly , if we change the LMQC fr om 2 to 3, the refr esh time also changes. The refr esh time in seconds is (LMQI/ 1 0) * LMQC = 255/ 1 0 * 3 = 76.5 seconds Manager Switch 1> set ip i gmp lmqc=[...]

Page 75 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Robustness V ariable Robustness V ariable What this counter does Th e Ro b us t ne s s V ar i ab l e ( R V ) al l ow s yo u to t u ne fo r th e e xp ec t ed p a cke t l o ss o n a s ub n e t. I f y ou expect a subnet to be lossy , you can incr ease the R V . I[...]

Page 76 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and count ers > Default Query Inter val Default Quer y Inter v al What this timer does T o maintain an accurate picture of group membership , the Querier periodically sends General Queries to all its IGMP interfaces. Th e Default Quer y Inter val is the gap betw een General [...]

Page 77 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Quer y Response Interval Quer y Response Inter val What this timer does The Quer y Response Inter val determines the lo ngest time clients can take to reply to a General Quer y . The Querier inserts the Quer y Response Inter val into General Quer y messages. C[...]

Page 78 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Default Timeout Inter val Default Timeout Inter val The Default Timeout Inter val is ref erred to as the Gr oup Member ship Inter val in RFC 2236 . What this timer does The Default Timeout Inter val spec ifies the length of time before the router or switch del[...]

Page 79 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Default Timeout Inter val Defaults First, the follo wing output shows the default settings. The Default Timeout Inter val = (2* 1 25) + ( 1 00/ 1 0) = 260 seconds. Incr ease Default Quer y Inter val Next, change the Default Quer y Inter val to 1 30 seconds. Th[...]

Page 80 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Default Timeout Inter val Incr ease Quer y Response Inter val Next, change the Quer y Response Inte r val to 200 tenths of a second. The Default Timeout Inter val = (2* 1 30) + (200/ 1 0) = 280 seconds. Reduce Inter vals Next, reduce the Default Query Inter v [...]

Page 81 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Default Timeout Inter val Over ride Default Timeout Inter val T o suppor t existing configurations and for maxi mum flexibility , y ou can manually o verride the Default Timeout Inter val. W e do not r ecommend this. The warning message also displa ys when the[...]

Page 82 | AlliedW are™ OS How T o Note: IGMP Configurable IGMP timers and counters > Default Timeout Inter val Earlier software ver s i o ns With software versions earlier than 28 1 -03 and 2.9. 1 , you need to man ually calculate and change the Default Timeout Inter val if you change an y of the Robustness V ariable , the LMQC , the Default Q[...]

Page 83 | AlliedW are™ OS How T o Note: IGMP Example of bad choices for timer values > Example Example of bad choices for timer values It is generally unwise to change an y of the defa ult IGMP settings unless you ha ve advanced knowledge of how IGMP works. As "Timer and counter relationships" on page 69 describes, most of the timers[...]

Page 84 | AlliedW are™ OS How T o Note: IGMP Example of bad cho ices for timer values > Pr oblem 1 : Last Member Query Inter val too shor t Pr oblem 1 : Last Member Quer y Inter val too shor t The Last Member Q uer y Inter val was set to 5, using the command: set ip igmp lmqi=5 This value is incredibl y low—actually 5 tenths of a second (hal[...]

Page 85 | AlliedW are™ OS How T o Note: IGMP Example of bad cho ices for timer values > Pr oblem 3 : Default Timeout Interval too shor t Note that the Quer y Response Inter val is specif ied in 1 / 1 0 second units on the command line and in output of sho w ip igmp , but in units of seconds in the above f ormula. In this example , the Quer y R[...]

Page 86 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Example Stopping snoopers fr om snooping non-IGMP messa ges Some networks include r outers that ha ve no inter est in IGMP , but still generate multicast messages by running pr otocols lik e OSPF . When a Snooper r ece ives m ulticast messages fro[...]

Page 87 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Example Switch 1 is an IGMP Querier . Switch 2 is an IGMP Snooper . Switch 3 is also an IGMP Snooper . X Configur e switch 1 set system name="Switch 1" # STP general configuratio n enable stp=default set stp=default mode=rapid set stp=de[...]

Page 88 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Example The r outer uses OSPF . With the abov e configuration, the router sends O SP F m es sa g e s t o sw i t ch 2. A s th e f ol l ow in g outputs show , this means that: z switch 2 designates por t 24 an All Groups por t z switch 2 f orwards t[...]

Page 89 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Example Manager Switch 3> show igmpsnoopin g IGMP Snooping -------------------------- ---------------------------------------------- Status ................... ........ Enabled Disabled All-groups ports ........ None Vlan Name (vlan id) ..... d[...]

Page 90 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Pr ev enting an All Groups ent r y for a por t Pr e venting an All Gr oups entr y for a por t This section stops por t 24 fr om being in switch 2’ s All Gr oups entr y , then adds it back again. Disabling All Gr oups entr y for a port Y ou can a[...]

Page 91 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Pr ev enting an All Groups ent r y for a por t Enabling All Gr oups entr y again T o further explore the system we will next r ev erse the process and follo w switch 2 while gr oup entries time out and th e switch star ts transmitting traffic for [...]

Page 92 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Pr ev enting an All Groups ent r y for a por t 4. Displa y por t 24’ s packet counters, which sho w that only a fe w multicast pack ets ha v e been transmitted on the por t. 5. Check the gr oup entr y timeout values again. Manager Switch 2> s[...]

Page 93 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Pr ev enting an All Groups ent r y for a por t 6. Enable IGMP debugging. 7. Obser ve the debugging output, which shows that the gr oup 224. 1 2. 1 3. 1 4 was deleted when its timer expir ed, th en was immediately added in again. 8. Check the gr ou[...]

Page 94 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Pr ev enting an All Groups ent r y for a por t 9. Displa y por t 24’ s packet counters, which sho w that many m ulticast packets ha ve been transmitted on the port . In summar y , when a port receives the All Groups designation, a stream is sent[...]

Page 95 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Contr olling which ad dresses cr eate All Groups entries Contr olling which addr esses cr eate All Gr oups entries The router or switch ad ds a por t to its All Grou ps list when it determin es that the port has a r outer attached to it. This exam[...]

Page 96 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Contr olling which ad dresses cr eate All Groups entries Configuring switch 2 The example below shows ho w to tailor the list of r outer addresses on switch 2. In summary , y ou do this by using the commands: set igmpsnooping routermode=ip delete [...]

Page 97 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Contr olling which ad dresses cr eate All Groups entries Looking at the abov e outputs, note that debu gging did not print out any messages about the OSPF r outer after we re moved the addr ess, but it did tell us when the por t had been r emoved [...]

Page 98 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Contr olling which ad dresses cr eate All Groups entries Configuring switches 1 and 3 The output of the command sho w igmpsnooping , abov e , shows that switch 2 is still r eceiving the multicast group 224. 1 2. 1 3. 1 4 ev en though it has no por[...]

Page 99 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Contr olling which ad dresses cr eate All Groups entries Returning to the default list T o re turn to the default list, change the router mode to default . If we then go back to ro ut er m o d e = i p , we ar e stil l left with the default set of [...]

Page 100 | AlliedW are™ OS How T o Note: IGMP Stopping snoopers fr om snooping non-IGMP messages > Contr olling which ad dresses cr eate All Groups entries Using the other routermode options As described earlier , routermode=multicastr outer is just a shortcut for the two IP addr esses for D VMRP and PIM. The mode routermode=none stops an y re[...]

Page 101 | AlliedW are™ OS How T o Note: IGMP Statically sp ecifying that a port is a router port > Example Statically specifying that a port is a r outer por t Since softwar e versions 28 1 -04 and 29 1 -0 4 , y ou can statically configure particular ports as multicast r outer ports. This featur e is useful in some unusual ne twork configurat[...]

Page 102 | AlliedW are™ OS How T o Note: IGMP Statically sp ecifying that a port is a router port > Example 3. Statically ad d por t 6 as a ro uter port attached to VLAN 1 . The abov e output show s that por t 6 has joined port 50 as an All Gr oups port. Also note that the Entr y timeout is infinity . This timeout of in finity only applies to [...]

Page 103 | AlliedW are™ OS How T o Note: IGMP IGMP debugging > Example IGMP debugging In this section, we shall examine the debuggin g messages that the r outer or switch outputs when certain events occur while debugging is enabled. T o enable debugging, use the command: enable ip igmp debug Example This example uses the same netw ork configur[...]

Page 104 | AlliedW are™ OS How T o Note: IGMP IGMP debugging > Example Client 2 sends a Lea ve message for group 224. 1 2. 1 3. 1 4. Switch 1 sees the Leav e messag e on vlan 1 00 (port 49). The por t is in a state of “d efer red dele tion” because of the Last Member Quer y process (see "Last Member Query Count and Last Member Quer y [...]

Page 105 | AlliedW are™ OS How T o Note: IGMP IGMP debugging > Example Client 2 sends a Memb ership Report for gr oup 224. 1 2. 1 3. 1 4. Switch 1 sees the r eport on vlan 1 00 (port 49) and adds an entr y . The entr y eventuall y expires. Switch 3—a Snooper—sees a V ersion 2 Membership Quer y message on vlan 1 00 fr om the Querier and for[...]

Page 106 | AlliedW are™ OS How T o Note: IGMP IGMP debugging > Example This example also shows what debugging outp ut looks lik e when the Snooper re ceives a General Quer y . The Querier sends the Genera l Query to the destination address 224.0.0. 1 (the IGMP Quer y address) and the Snooper tells us that it has added the “r outer” port to[...]

Page 107 | AlliedW are™ OS How T o Note: IGMP IGMP debugging > Example When IGMP debugging is enabled, the command sho w ip igmp gives mor e information about static IGMP associations, as show n in bold in the following output. See "Explanation of Static IGMP" on page 51 f or more information about static associations. X Output for s[...]

Page 108 | AlliedW are™ OS How T o Note: IGMP Appendix: STP state > Switch 1 Appendix: STP state In most of the e xamples in this document, the s w itches are configur ed in a loop and are all in the same VLAN. T o pre vent pack ets from looping the netw ork, STP is configured. The STP state on each switch is giv en in the following output scr[...]

Page 109 | AlliedW are™ OS How T o Note: IGMP Appendix: STP stat e > Switch 2 Switch 2 Manager Switch 2> show stp =default port=25-26 STP Port Information -------------------------- ---------------------------------------------- STP ..................... default STP Status ............ ON Port .................. 25 RSTP Port Role ...... Roo[...]

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