Hello!
This is probably due to BIRD updating the "current real time" once per
IO cycle which is in idle case once per 3 seconds. This may change in
future versions, anyway I wouldn't trust the time as an indicator of
route change at all.
The most reliable way is to write your own protocol inside BIRD <^-^>
and get the updates from the source directly. Anyway, it takes some
work. (We plan to make this method simple, hopefully in near future.)
Another quite reliable way is to export the routes to kernel and then
run 'ip monitor' or 'route monitor' command to read them. This anyway
drops some attributes.
Or you can use the script to compare the MD5 of "show route all"
outputs, yet you should probably s/\d\d:\d\d:\d\d/<TIME>/ (or something
like that). The output is also done by walking over a hash table which
may rehash sometimes and change the overall order of prefixes. Anyway,
rehashing happens only when a route is changed (no sudden rehashes out
of nothing).
Maria
On 11/25/21 9:51 PM, [email protected] wrote:
Hi all,
If I do several consecutive "show route" queries, the timestamp keeps
changing back and forth, by about a second. Example:
0.0.0.0/0 via x.x.x.x on em2.100 [aapt 05:20:28] * (100) [AS2764i]
0.0.0.0/0 via x.x.x.x on em2.100 [aapt 05:20:28] * (100) [AS2764i]
0.0.0.0/0 via x.x.x.x on em2.100 [aapt 05:20:27] * (100) [AS2764i]
0.0.0.0/0 via x.x.x.x on em2.100 [aapt 05:20:28] * (100) [AS2764i]
I notice (via public route servers) that Quagga and FRRouting seem to do
the same thing. Example:
Last update: Thu Nov 25 18:20:31 2021
Last update: Thu Nov 25 18:20:30 2021
Last update: Thu Nov 25 18:20:30 2021
Last update: Thu Nov 25 18:20:31 2021
Does Bird do this in order emulate some convention (like perhaps
something Cisco has done for decades), or is there some other reason
it's displaying an inconsistent timestamp?
I have a script that compares the md5 of the current output with the
previous minute to decide whether to log the routing table, but because
of this quirk the md5 changes almost every time...
So, is this a bug, or feature? :) And is there some other reliable way
to determine that Bird's routing table has changed?
Thanks.
