Hi,
I was able to catch a strange behaviour of my Mikrotik PPPoE server. Unfortunately I dont't have information about client side PPPoE. Anyway, I don't think that it is ok for PPPoE server accept 0.0.0.0/0 route prefix from any client. I haven't found any option for pppoe-server to allow or disallow this. For me it looks like a BUG in IPCP implementation.
Below is log fragment:
Feb 21 18:46:24 Mk-DZ-06 <pppoe-4she_224>: connected
Feb 21 18:46:24 Mk-DZ-06 Interface change
Feb 21 18:46:24 Mk-DZ-06 interface=<pppoe-4she_224>
Feb 21 18:46:24 Mk-DZ-06 status=UP,RUNNING
Feb 21 18:46:24 Mk-DZ-06 mtu=1480
Feb 21 18:46:24 Mk-DZ-06 Interface <pppoe-4she_224> changed mtu
Feb 21 18:46:24 Mk-DZ-06 mtu=1480
Feb 21 18:46:24 Mk-DZ-06 Interface change
Feb 21 18:46:24 Mk-DZ-06 interface=<pppoe-4she_224>
Feb 21 18:46:24 Mk-DZ-06 status=UP,RUNNING
Feb 21 18:46:24 Mk-DZ-06 mtu=1480
Feb 21 18:46:24 Mk-DZ-06 Begin calculation
Feb 21 18:46:24 Mk-DZ-06 Link up
Feb 21 18:46:24 Mk-DZ-06 interface=<pppoe-4she_224>
Feb 21 18:46:24 Mk-DZ-06 Update
Feb 21 18:46:24 Mk-DZ-06 interface=<pppoe-4she_224>
Feb 21 18:46:24 Mk-DZ-06 Added candidate route
Feb 21 18:46:24 Mk-DZ-06 dst-prefix=0.0.0.0/0
Feb 21 18:46:24 Mk-DZ-06 attributes
Feb 21 18:46:24 Mk-DZ-06 protocol=DYNAMIC
Feb 21 18:46:24 Mk-DZ-06 distance=1
Feb 21 18:46:24 Mk-DZ-06 scope=30
Feb 21 18:46:24 Mk-DZ-06 target-scope=10
Feb 21 18:46:24 Mk-DZ-06 interface-next-hop=15743800
Feb 21 18:46:24 Mk-DZ-06 origin-type=DYNAMIC
Feb 21 18:46:24 Mk-DZ-06 Select route
Feb 21 18:46:24 Mk-DZ-06 dst-address=0.0.0.0/0
Feb 21 18:46:24 Mk-DZ-06 attributes
Feb 21 18:46:24 Mk-DZ-06 protocol=DYNAMIC
Feb 21 18:46:24 Mk-DZ-06 distance=1
Feb 21 18:46:24 Mk-DZ-06 scope=30
Feb 21 18:46:24 Mk-DZ-06 target-scope=10
Feb 21 18:46:24 Mk-DZ-06 interface-next-hop=15743800
Feb 21 18:46:24 Mk-DZ-06 origin-type=DYNAMIC
Feb 21 18:46:24 Mk-DZ-06 End calculation
Feb 21 18:46:24 Mk-DZ-06 Begin redistribution
Feb 21 18:46:24 Mk-DZ-06 Accept update 0.0.0.0/0
Feb 21 18:46:24 Mk-DZ-06 Commit prefix 0.0.0.0/0