11-05-2002 03:50 PM - edited 03-02-2019 02:39 AM
In a typical campus network with layer-3 core & distribution layers and a layer-2 access layer and lots of equal-cost paths we have a situation with multicast (PIM-SM).
The distribution layer is provided by two 7600 routers running HSRP & PIM-SM - say Distribution-Router-A has the highest IP address and is the PIM & IGMP DR for the Access-Layer VLAN, Distribution-B is the IGMP querier.
When a sender begins transmitting to a group the DR (Distribution-A) unicasts a register to the RP connected to the Core (separate router). The RP then joins the shared tree back to the source, due to the equal-cost paths this join turns-up on the non-DR router for the VLAN - the RP sent a PIM join to Core-2, Core-2 has equal-cost paths to the source VLAN via Distribution-A and Distribution-B and it just so happens the next-hop to Distribution-2 has the higher IP address so this is chosen as the RPF.
My question is this - is this supposed to happen? how does the non PIM-DR for the VLAN handle this ? Is it OK?
This is all in the design-stage at the moment so I'm open to suggestions.
Andy
11-11-2002 02:17 PM
The following links I hope will give an idea for your queries
IP Multicast Load Splitting Across Equal Cost Paths
http://www.cisco.com/warp/public/cc/techno/protocol/ipmu/prodlit/ipmul_an.htm
How to Configure a RP for PIM Sparse Mode
http://www.cisco.com/warp/public/cc/pd/iosw/prodlit/rppim_rg.htm
Why Auto-RP and How to Deploy It Painlessly
http://www.cisco.com/warp/public/cc/techno/protocol/ipmu/prodlit/yauto_an.htm
11-12-2002 07:16 AM
I have lots of information on PIM, Auto-RP, Anycast etc etc The problem is I can't find anything on CCO that explains the situation I describe. Equal-cost paths yes, but not with 2 routers on a common Ethernet Segment and equal-cost paths as this introduces the PIM & IGMP DR. There is something described regarding the Non-RPF router scenario and CEF fast dropping but this specific problem at the moment is a mystery.
Anyone?
12-09-2002 08:17 AM
Is there a problem that it's not working? I did not understand your question 100%
For design-stage it's useful to have:
The HSRP address on the highest IP address so PIM DR and HSRP is on same box.
There is a command that you can configure the DR on the box you like, but I don't no what the command is or in what ios version its in.
Regards
Gerrit Frans
12-10-2002 03:26 PM
Gerrit
My question was just to clarify that there should not be a problem when a non PIM/IGMP DR router that is directly connected to sources and/or receivers is actively forwarding traffic onto the network due to equal-cost unicast-routing paths and PIM's path selection technique of highest IP address if there are equal-cost paths. I wanted to know if the DR would 'object' to this happening, or would it cause a problem with paths not being pruned off?
Andy
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