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Explanation of mroute flags?

Answered Question
Aug 11th, 2009
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Would someone point me to a white sheet, or section of a config guide, that would explain all the flags in the 'sh ip mroute' display? I looking for something more enlightening than just a discription of the flag; ie. "'The SPT-bit set' means the Shortest Path Tree bit is set," but actually explain what causes the flags, and caveats if some flags are set and others aren't.

NGT-SW3750-CD-MDF#sh ip mroute

IP Multicast Routing Table

Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,

L - Local, P - Pruned, R - RP-bit set, F - Register flag,

T - SPT-bit set, J - Join SPT, M - MSDP created entry,

X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,

U - URD, I - Received Source Specific Host Report, Z - Multicast Tunnel

Y - Joined MDT-data group, y - Sending to MDT-data group


Correct Answer by jbrenesj about 8 years 1 week ago

This is the best I have.


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Overall Rating: 5 (4 ratings)
jim_berlow Tue, 08/11/2009 - 08:55
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Well, here is the official command reference for "show ip mroute" command:


Now if your like me - that still doesn't tell you "jack" about why such and such would be shown. I personally refer to a multicast book by Beau Williamson ("Developing IP Multicast Networks") which gives better detail about those flags. I can say that book is considered the "bible" on multicasting and will probably answer almost all your questions.

I hope that helps.


jkeeffe Tue, 08/11/2009 - 09:09
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Thanks for the tip on the book - looks like something I should purchase.


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