Comment 1 for bug 1443483

Guessing it's because neutron is use eventlet wsgi server and its max URI size is MAX_REQUEST_LINE = 8192
so yes, it's a bug , but not sure a POST can be used since it's using neutron API (still search whether neutron has this kind of API)

this is a log in nova says following

39 # NOTE: Neutron client has a max URL length of 8192, so we have
 40 # to limit the number of IDs we include in any single search. Really
 41 # doesn't seem to be any point in making this a config value.