--- Begin Message ---
Hello,
Last time I tested it, "from metric 0" works only if MED is present and
equals 0.
Back then (around JUNOS 17) I developed a policy to detect missing MED
which exploits metric2 rollover (basically, subtracting 1 from missing
MED results in MED==4294967295)
Example below:
regress@R1# show policy-statement CHECK_MED_IMPORT
term CHECK_IF_MED_EXISTS_AND_0 {
from {
metric 0; {## accept if MED present && 0
}
then accept;
}
term MED_DECREMENT {
then {
metric {
expression {
metric multiplier 1 offset -1; ## turns absent MED into
2^32-1
}
}
next term;
}}
term CHECK_IF_MED_ROLLED_OVER {
from metric 4294967295;
then accept; ## sets missing MED to 4294967295 but You can set it to
smthg else
}
term RESTORE_ORIGINAL_MED {
then {
metric add 1;
}
}
Thanks
Alex
------ Original Message ------
From: "Baldur Norddahl" <[email protected]>
To: "Juniper List" <[email protected]>
Sent: 19/09/2020 22:49:07
Subject: Re: [j-nsp] set MED only on empty
Hello
Metric zero should work, I do not know why I did not think of that.
Thanks,
Baldur
Den lør. 19. sep. 2020 kl. 21.13 skrev Eduardo Schoedler <[email protected]
:
Hi Baldur,
Try match metric, with some tests you can define empty (maybe zero?).
https://www.juniper.net/documentation/en_US/junos/topics/usage-guidelines/policy-configuring-match-conditions-in-routing-policy-terms.html
Regards.
Em sáb., 19 de set. de 2020 às 12:59, Baldur Norddahl <[email protected]>
escreveu:
Hello
I want to set MED (metric) only when the peer did not specify a MED value.
The idea being that peers that set MED have a reason for their choice, but
if no MED value is set, I am going to set it to MED=(latency_to_peer_in_ms
+ 1000). That way we will prefer the route with lowest latency.
But I can not figure out how to match on no MED value in a policy. There
must be a way to do this?
Thanks,
Baldur
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--
Eduardo Schoedler
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