In our colocation we have multiple linux servers with a public uplink connected to a juniper MX40 (that we can not control) and an internal link each.

Sometimes we get incoming UDP flooding saturating the public link of one of the servers. When that happens on a set of (important) servers we want to shed the load on the link as fast as possible.

Right now we use a server hosting less important services and send some gratuitous ARP packets with arping so the traffic then hammers the link of a less important service.

We would like it better to get the juniper to drop the traffic instead (with "no route to host" or whatever). We could accomplish that by just no longer announcing the IP (shutting down the IP alias) but the timeout of the MAC table is 300s, which is too much.

Is there another way to let the juniper drop the MAC entry?

1 Answer 1


Turns out the easiest way to drop all entries from the MAC/SAT table is link renogtiation. That clears the SAT table (tested and confirmed with Cisco routers).

Just hit ethtool -r ethX and the routers SAT tables was empty for the port.

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