Comment 2 for bug 1927097

For completeness, not that even after patching cephadm to parse ip route ls properly in the BGP/ECMP case we still fail with:
May 06 10:33:31 ctrl-1-0.bgp.ftw systemd[1]: Started Ceph mgr.ctrl-1-0.bgp.ftw.hpwvwv for 4b5c8c0a-ff60-454b-a1b4-9747aa737d19.
May 06 10:33:31 ctrl-1-0.bgp.ftw conmon[74961]: debug 2021-05-06T10:33:31.388+0000 7f9e29044500 0 set uid:gid to 167:167 (ceph:ceph)
May 06 10:33:31 ctrl-1-0.bgp.ftw conmon[74961]: debug 2021-05-06T10:33:31.388+0000 7f9e29044500 0 ceph version 16.2.0 (0c2054e95bcd9b30fdd908a79ac1d8bbc3394442) pacific (stable), process ceph-mgr, pid 7
May 06 10:33:31 ctrl-1-0.bgp.ftw conmon[74961]: debug 2021-05-06T10:33:31.389+0000 7f9e29044500 -1 unable to find any IP address in networks '172.31.0.1/32,172.31.0.1/32' interfaces ''
May 06 10:33:31 ctrl-1-0.bgp.ftw systemd[1]: libpod-1c9f60cdb0bba3d228d24bbc8dbdd4be6091c9dca481577cf233376972f7963d.scope: Succeeded.
May 06 10:33:31 ctrl-1-0.bgp.ftw systemd[1]: libpod-1c9f60cdb0bba3d228d24bbc8dbdd4be6091c9dca481577cf233376972f7963d.scope: Consumed 64ms CPU time

This is because https://github.com/ceph/ceph/blob/master/src/common/pick_address.cc#L210 and https://github.com/ceph/ceph/blob/master/src/common/pick_address.cc#L147 do not cater to environments where the ip is a /32 and the routes are then just propagated via bgp.