From: john matijevic (john.matijevic@gmail.com)
Date: Wed May 04 2005 - 16:52:27 GMT-3
Hello John,
As far as your scenerio I would highly recommend that you lab it out if you
can, you will retain it better that way. But to answer your question, yes
you can set the metric by using the route-map or setting it when you
redistribute into ospf. And when you do a show ip route, you should be able
to verify that the metric is set correctly.
Here is some documentation from Cisco that might help clarify:
Sincerely,
John
Control Default Metrics
In Cisco IOS Release 10.3 and later, by default, OSPF calculates the OSPF
metric for an interface according to the bandwidth of the interface. For
example, a 64K link gets a metric of 1562, while a T1 link gets a metric of
64.
The OSPF metric is calculated as *ref-bw* divided by *bandwidth*, with *
ref-bw* equal to 108 by default, and *bandwidth* determined by the *
bandwidth* command. The calculation gives FDDI a metric of 1. If you have
multiple links with high bandwidth, you might want to specify a larger
number to differentiate the cost on those links. To do so, perform the
following task in router configuration mode:
The following example redistributes RIP routes into OSPF. These routes will
be redistributed into OSPF as external link state advertisements with a
metric of 5.
router ospf 109
redistribute rip route-map rip-to-ospf
!
route-map rip-to-ospf permit
set metric 5
When you do a show ip route, you are correct the first number is the
administrative distance and the second number is the metric.
OSPF Cost
The cost (also called metric) of an interface in OSPF is an indication
of the overhead required to send packets across a certain interface.
The cost of an interface is inversely proportional to the bandwidth of
that interface. A higher bandwidth indicates a lower cost. There is
more overhead (higher cost) and time delays involved in crossing a 56k
serial line than crossing a 10M ethernet line. The formula used to
calculate the cost is:
-
cost= 10000 0000/bandwith in bps
For example, it will cost 10 EXP8/10 EXP7 = 10 to cross a 10M Ethernet
line and will cost 10 EXP8/1544000 = 64 to cross a T1 line.
By default, the cost of an interface is calculated based on the
bandwidth; you can force the cost of an interface by using the *ip
ospf cost <value> interface sub-* command.
http://www.cisco.com/en/US/products/sw/iosswrel/ps1826/products_configuration
_guide_chapter09186a00800877d7.html#wp2294
http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9
e.shtml#t6
On 5/4/05, John Matus <john_matus@hotmail.com> wrote:
>
> i forget, is ospf cost synonomous with "metric"? when i'm looking at the
> routing table and i see:
> 10.1.1.0/24 <http://10.1.1.0/24> [110/210], is it [administrative
> distance/ospf cost], or is the
> second metric something entirely different?
>
> and if i'm redistribuing routes into ospf with a route-map and i set the
> metric to 500, is that setting the "cost" to 500?
>
> TIA.
>
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-- John Matijevic, CCIE #13254 U.S. Installation Group Senior Network Engineer 954-969-7160 ext. 1147 (office) 305-321-6232 (cell)
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