[Xorp-users] Fwd: Route redistribution issue

Phil Wiggins phil.wiggins at gmail.com
Sat Aug 18 09:21:51 PDT 2012


Igor...apologies for the terrible formatting in the previous email.  I've
re-added the OSPF-->RIP and RIP-->OSPF cost conversion mapping between
domains that could be used.

Phil

On Wed, Jul 25, 2012 at 12:55 AM, Phil Wiggins <phil.wiggins at gmail.com>
wrote:
> On Mon, Jul 23, 2012 at 8:47 AM, Igor Maravić <igorm at etf.rs> wrote:>
>>
>> > Suggestion #2 - Further, for redistributing 16/32-bit metrics a "bit
>> > shift"
>> > function would be helpful for the policy tools to use.
>> >
>>
>> This shouldn't be much of problem to implement.
>> Could you explain your idea in little more detail.
>> If I understood correctly in this case you would shift OSPF metric by
>> 1, or 2, bits
>> and you would got metric that can be used by RIP?
>>
>> (11 >> 1 == 5,
>> 21 >> 1 == 10)
>
> To work with the metrics for route redistribution between separate metric
> spaces, it would be useful to have multiply (mult) and divide (div)
> functions.  Slightly more flexible would be a combination of conversion
> tools to do something like ax+b where a is a multiply factor for metric
> space conversion, x is the source metric, and b is some addition.
>
> Bit shift would be shift left (shiftl) and shift right (shiftr) which
could
> provide some potential savings for embedded environments.  The examples
that
> you provide are exactly what was intended.
>
> An example for conversion between RIP and OSPF space, RIP to OSPF
Conversion
> could be a simple multiply by 4096.
RIP Metric  OSPF Cost
0               0
1            4096
2            8192
3           12288
4           16384
5           20480
6           24576
7           28762
8           32768
9           36864
10          40960
11          45056
12          49152
13          53248
14          57344
15          61440
16          65536


> OSPF to RIP Conversion could be a divide by 4096 possibly with a modulo or
> roundup/rounddown
OSPF Cost Range       RIP Metric
0                      0
1 – 4096               1
4097 – 8192            2
8193 – 12288           3
12289 – 16384          4
16385 – 20480          5
20481 – 24576          6
24577 – 28762          7
28763 – 32768          8
32769 – 36864          9
36865 – 40960         10
40961 – 45056         11
45057 – 49152         12
49153 – 53248         13
53249 – 57344         14
57345 – 61440         15
61441 and up          16
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