On 4/30/20 12:30 AM, Mark Tinka wrote:
On 29/Apr/20 17:04, Mike wrote:
Hello,
Is there a recommended 'modern default' for ip ospf auto-cost
reference-bandwidth, to account for the fact that modern networks have
1g and faster interfaces?
My core equipment all has 10G and 1G interfaces today, and it seems
to me that if I set the reference-bandwidth to 100gbps, Im not losing
anything, but gaining a useful distinction between the modern
1g,10g,40g,and 100g interfaces of today. I understand the necessity of
setting this on all routers in the network, however, I do have some
older equipment (cisco 7201) doing T1 aggregation that also has 1g
interfaces with nothing higher, so I am wondering the practicality of
maybe just skipping this default change on that and like gear? These
devices are at the edge and further only have single uplink connections
to the core so it would seem safe to not worry about this here.
When we moved to IS-IS in 2007, we decided to set our reference
bandwidth to 1Tbps (not in the routers, but as a concept).
My recommendation would be not to set the reference in the network.
Rather, have it as an architecture concept and deliberately design
metrics off of your reference. 1Tbps seemed reasonable in 2007. Who
knows, maybe 10Tbps is reasonable in 2020 (with the downside being that
your metrics will be very high for very slow links).
Mark.
My recommendation would be to set the default such that most or all of
the links would default to a metric higher than what your designed
metrics would be. Let the defaults protect you so that if a metric is
missed, the default behavior is not to let the new link become instantly
"best".
pt
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