[j-nsp] Filtering rib-group imported direct routes?

[Phil Bedard]

Can you apply an import policy to the rib group to weed those out?  Also the newer versions of Junos support Cisco PBR like functionality straight from the firewall filter instead of having to deal with the instances, so traffic goes directly out an interface vs. being subject to LPM in another routing table.  

Phil

-----Original Message-----
From: "Chris Woodfield" <rekoil at semihuman.com>
Sent: ‎11/‎15/‎2014 3:14 PM
To: "juniper-nsp at puck.nether.net" <juniper-nsp at puck.nether.net>
Subject: [j-nsp] Filtering rib-group imported direct routes?

Hi,

I’m currently managing a setup where we’re at our edge, we're punting packets to a routing-instance based on firewall matches in order to separate traffic between outside client traffic (which needs to be routed through the LB on return) and other internet-facing outbound. We have rib-groups configured for our routing-instances to import the direct and local routes, like the below (simplified) config example:

routing-options {
    interface-routes {
        rib-group {
            inet fbf-groups;
	}
    }
    ...
    rib-groups {
        fbf-groups {
            import-rib [ inet.0 lb1.inet.0 ]
        }
    }
}
...
firewall {
    family inet {
        filter BOUNCE_TO_LB
            from { 
		protocol tcp;
                source-port [ 80 443 ];
            }
	    then {
                routing-instance lb1;
            }
        }
    }
}
...
routing-instances {
    lb1 {
        instance-type forwarding;
        routing-options {
            static {
                route 0.0.0.0/0 next-hop 1.2.3.4;
            }
        }
    }
}

The "lb1" routing-instance is simply a default route to the LB's gateway IP which is a directly connected interface to the router.

(This design is documented here: https://www.juniper.net/documentation/en_US/junos12.3/topics/example/logical-systems-filter-based-forwarding.html)

The problem I'm having is that because this setup imports all direct and local routes into the routing instance, packets that are punted to the routing instance that are destined for other directly connected hosts bypass the default route and get forwarded directly to the end host. For example, if I have a host hanging off of interface xe-2/0/0 with address 2.2.3.4/24, and I look in the routing-instance's table, I see:

edge-rtr> show route table lb1.inet.0   

lb.inet.0: XXX destinations, XXX routes (XXX active, 0 holddown, X hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[Static/5] 37w1d 15:53:29
                    > to 1.2.3.4 via xe-1/0/0
2.2.3.4/24         *[Direct/0] 11w3d 10:42:47
                    > via xe-2/0/0.0
2.2.3.1/32         *[Local/0] 11w3d 10:42:47
                      Local via xe-2/0/0.0

So a packet with dest IP 2.2.3.4 goes directly to the host instead of going to the LB, which means it has the real host IP and not the VIP's IP as its source, which means no worky worky.

So the question I have is this - is there a way to filter the direct and local routes that are imported into a routing instance? In this case, I'd only want the direct route for the subnet containing 1.2.3.4, and no other direct routes.

Alternatively, would it be possible to *not* import any direct routes into the routing-instance (i.e. deleting the rib-groups syntax altogether) and instead add the direct and/or local route manually to the routing instance, so I can ensure that only the direct routes I need to resolve the next hop make it into the routing instance?

TIA,

-Chris





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