From: Howard C. Berkowitz (hcb@xxxxxxxxxxxx)
Date: Thu Feb 14 2002 - 19:19:35 GMT-3
>I was wondering how you define the bandwidth on a multipoint FR connection
>from the hub, which is running OSPF ?
>
>for instance, if you have 2 PVC's over the multipoint connection, one is
>1544k, the other is 64k both give you access to the same Ethernet segment on
>the other side of the routers, to ospf at the hub, they are both equal ?
>
>>From the spoke perspective this wont matter if bandwidth is set correctly.
>
>any thoughts ?
>
>RA.
ip ospf cost overrides the bandwidth-based calculation. So, assuming
you wanted to keep the bandwidth correct so show commands and SNMP
counters produce correct results, you would code both the real
bandwidth and an equal ospf cost on both interfaces.
Of course, you will have to be careful that only the spoke router
connects to these segments, if you set (reasonably) a cost of 1. The
rest of the area will think these are 100 Mbps links, but if they are
the only way to reach the segment, the routing will still be what you
want, although you will have strange metrics composed of a
combination of bandwidth-based and cost-based components.
If you do have multiple paths to the segments, you might have to
implement cost-based interfaces everywhere in the area. I assume
it's some sort of stubby area. If it were a regular area, you might
need to use the cost-based everywhere.
This isn't necessarily the worst thing in the world. I dealt with one
military network where they had both 2.4 Kbps shipboard radio links
and Gigabit Ethernet. We established a cost table that grouped link
costs into broad categories, depending on whether there would be a
choice among links or not. When doing so, be sure to leave space
between the chosen costs and at the top and bottomo of the range!
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