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Home > Archive > CCNP > October 2004 > number of links
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| peterd 2004-09-30, 7:22 am |
| Hi,
the formula for number of links in a network is n(n-1)/2...
In OSPF we can use DR's and BDR's to reduce the number of links, ie full mesh isn't required.
Is there a formula for number of links when using BR/BDR?
I've got some practice questions off a site and one of them asks the number of links for five routers, when one is a DR and one is a BDR.
It's easy enough to draw out on paper and count the links...seven, (three routers, one link from each to the DR and another to the BDR plus one link bewteen the DR and BDR) but then something is niggling me that the answer is eight.
I vaguely recall something from about four years ago when I last looked at this...the DR and BDR set up two links between each other.
Or am I cracking up?
Regards
Peter | |
| ZacDogg 2004-09-30, 10:28 am |
| I've don't recall a formula, but to create one I think it would be (n-2)2+1. Number of routers, minus 2 for the DR and BDR, mulitplied by 2 for the DRothers adjacency to the DR and BDR, plus one for the DR and BDR's adjacency.
Zac | |
| peterd 2004-10-04, 4:24 am |
| Hi,
have you ever read or heard anything about the DR and BDR setting up two links between themselves rather than just one?
Regards
Peter |
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