[j-nsp] arp from correct IP address

[Chris Kawchuk]

Ran into the same bug.

$junos-preffered-source-address for an unnumbered for BNG functions does NOT return the "closest/must suitable address" based on the IP+Subnet that was given the subscriber... contrary to the BNG template doucmentation. It just defaults the actual loopback of the router. (the dynamic template that gets created against a demux0.xxxx subscriber says $preffered of "NONE")

This means that things like Subscriber "ARP liveliness detection" doesn't work/cant work. (since the subscriber won't arp-respond to an ARP requests where the source isn't in the local subnet)

I've had a JTAC case open on this for 8 months. Sent full configs, built a full lab for them (so they could trigger it remotely), self full PCAPs.

MX204 + JunOS 18.3Rxxxx + BNG (DHCP/IPoE naturally)

Also on MX80 w/same code - so it's the BNG code, not the platform doing it.

- Ck.




> On 25 Jan 2020, at 10:27 pm, Baldur Norddahl <baldur at gigabit.dk> wrote:
> 
> Hello
> 
> I have a problem where some customer routers refuse to reply to arp from
> our juniper mx204. The arp will look like this:
> 
> 11:57:46.934484 Out arp who-has 185.24.169.60 tell 185.24.168.248
> 
> The problem is that this should have been "tell 185.24.169.1" because the
> client is in the 185.24.169.0/24 subnet. The interface is
> "unnumbered-address lo0.1" with lo0.1 having both 185.24.168.248 and
> 185.24.169.1 among many others. A Linux box would select the nearest
> address but apparently junos does not know how to do this.
> 
> Tried adding in "preferred-source-address $junos-preferred-source-address"
> but this just results in "preferred-source-address NONE" and does nothing.
> Also there is zero documentation on how junos will fill in that variable.
> 
> Is there a solution to this? Is there a radius variable I can set with the
> preferred source address?
> 
> Regards,
> 
> Baldur
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