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Home > Archive > CCNP > May 2002 > Multicast question
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| Author |
Multicast question
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| madfacker 2002-04-29, 4:15 pm |
| What is the difference between a Query router and a Designated router as far as multicast is concerned.
TIA | |
| SurfinUSA 2002-05-02, 2:30 pm |
| Here is my "guess", and Anyone please correct me if I am wrong: I have seen designator router in use with OSPF. It is the top dog, the one that updates via LSAs all other OSPFrouters. All OSPFrouters answer to the DR. As far a "query" goes, (and I havent read BGP enough, so maybe Im missing something), the only time I have seen "query" is in EIGRP, and that was when a feasable successor and backup feasable successor (is that term right?) were not availalbe, so the EIGRP router would send out via multicast a "query" to find another route.
Anyone else on this, because I feel like I may have missed something here. | |
| The Reamer 2002-05-02, 5:14 pm |
| In terms of Multicasting, a router will send out membership query messages to verify that there is at least one host on a segment still interested in the multicast traffic.
In OSPF, the designated router uses multicasts to update other routers.
HTH,
Reamer | |
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| According to Cisco:
"Multicast routers send IGMP host-query messages to discover which
multicast groups are present on attached networks.
Multicast routers elect a PIM designated router for the LAN (subnet).
The designated router is responsible for sending IGMP host-query messages to all hosts on the LAN. In sparse mode, the designated router also sends PIM register and PIM join messages toward the RP router."
Check out: http://www.cisco.com/univercd/cc/td...rt1/1cmulti.htm | |
| ZacDogg 2002-05-08, 7:11 am |
| The difference between a query router and a DR in multicast is that when IGMPv1 is being run there is no querier election process. It relies on on the multicast routing protocol to elect a DR, which becomes the querier. In IGMPv2 there is a querier election process so the DR has no importance. The querier and DR can be diff. routers. Membership reports will be addressed to the group address which will be heard by all participating routers. |
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