10-18-2011 04:23 PM
I am a technical writer at Juniper.
I am trying to write a new configuration example for PIM using rib-groups.
I came across a J-Net discussion about using rib-groups to populate inet.2.
In this discussion it shows a config that uses the import-rib statement to populate the inet.0 and inet.2 routing tables.
rib-group inet populate-inet2;
import-rib [ inet.0 inet.2 ];
In the currently existing Junos documentation the configuration example states “You must include the export-rib statement because inet.0 cannot be the default table for exporting routes into another table with the import-rib statement.”
user@host# edit routing-options rib-groups
user@host# set pim-rg export-rib inet.0
user@host# set pim-rg import-rib [ inet.0 inet.2 ]
So I am trying to figure out if the export-rib statement is really required or if the documentation is wrong.
If the export-rib statement is required, I need to explain why we need to export from inet.0 and import to inet.0.
Do you happen to know or can you tell me who might know?
Thanks in advance.
10-18-2011 05:01 PM
Perhaps this is it. (Roy’s sounds-good but who knows theory.)
PIM is the protocol.
inet.0 and inet.2 are the routing tables.
The export-rib statement exports routes from inet.0 into PIM
The import-rib statement imports the routes from PIM into inet.0 and inet.2
This accomplishes the goal of populating inet.2 with the desired routes.
The export-rib statement has no affect on the operation of PIM since PIM uses the inet.2 table for RPF and does not use it’s own protocol routes.
Sounds good, but I am just guessing.
10-27-2011 10:51 PM
I'm wondering if it's some type of hack due to the nature of PIM.
You'll notice that particular JNCIS book shows only using import inet.2 in the rib-group, as for PIM, it's only using the rib-group to determine what table it's supposed to use for RPF. The doc example you linked, actually uses inet.0 and inet.2 both for RPF, if I understand it right. This specific type of configuration (using inet.0 and inet.2 both) may have special gotcha's in the rib-group logic, which may require the export statement.
I'm by no means a PIM expert, though.