[j-nsp] MX80 - Control Plane, Bridge Domains

Andrei-Marius Radu andreir at gmail.com
Tue Oct 14 13:20:19 EDT 2014

Hit send too soon :)

Anyway I was trying to say that the more specific routes will drop incoming
packets and stop the router from ARPing.

Hope this helps,

On Tuesday, 14 October 2014, Andrei-Marius Radu <andreir at gmail.com> wrote:

> Hi Ritz,
> If you sure that specific addresses or ranges are not used at all (as
> opposed to machines currently offline but which might wake up at a later
> time) then you can configure more-specific static routes with a discard
> next-hop.
> On Tuesday, 14 October 2014, Ritz Rojas <ritzrojas at gmail.com
> <javascript:_e(%7B%7D,'cvml','ritzrojas at gmail.com');>> wrote:
>> We have a particular legacy setup that involves a couple of multi-net
>> bridge domains on an MX80 with a fairly decent number of networks attached
>> to multiple interfaces.  Example:
>> Bridge Domain
>> ===
>> > show configuration bridge-domains
>>     description Customer;
>>     domain-type bridge;
>>     vlan-id XXX;
>>     interface ge-1/0/0.0;
>>     interface ge-1/0/1.0;
>>     (multiple interfaces omiited, roughly 25 total);
>>     routing-interface irb.xxx
>> Interfaces
>> ===
>> > show configuration interfaces ge-1/0/0
>> description Customer;
>> encapsulation ethernet-bridge;
>> unit 0;
>> (repeat above for each bridge domain member)
>> IRB
>> ===
>> > show configuration interfaces irb.xxx
>> description Customer;
>> family inet {
>>     address;
>>     address;
>>     address;
>>     (additional addresses omitted);
>> The number of routed networks on the IRB is pretty large, >75.
>> The problem that we're seeing is when somewhat large-ish amounts of
>> traffic
>> gets directed to non-existing hosts on these multi-nets (say to
>> non-existing hosts numbered .100 to .200 in the 192.168.1/24 subnet, and
>> expand that by all the configured subnets), the control-plane on the MX80
>> seems to grind down to a halt.  ICMP RTT goes way up which alerts
>> monitoring services, and we've even seen the box drop IGP/BGP to it's
>> upstream device.
>> We've already slapped in some interface specific ARP policers, but ARP
>> policing won't really do anything for this issue, since the box itself is
>> sending ARP traffic *out* towards those non-existing hosts, and IIRC ARP
>> policing is an ingress interface function.  The box has a decent CoPP
>> filter, but this is data-plane traffic to the directly attached hosts in
>> the network, not necessarily to the interface itself (though it *is*
>> resulting in excessive control-plane traffic due to the ARP load, it would
>> appear) so I'm not sure we can solve this with CoPP.  We've also looked at
>> sticking in some BUM policers on the bridge domains (bridge-domain
>> blah/forwarding-options/flood), but that appears to be an ingress function
>> as well, and we haven't seen that help either.
>> Simply killing off and re-architect-ing this topology isn't currently an
>> option, though it's planned at some point.  I'm curious if anyone run into
>> this type of issue with this type of setup, and how did you solve it?
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