[c-nsp] Secondary IP address causing MTU reduction?

[Eric A Louie]

I encountered a strange problem that I'm hoping is a bug.
Directly connected routersMTU 9200Works fine with single IP addresses
As soon as I put a secondary address on both interfaces (one VLAN, one physical interface), the MTU allowed magically decreased to 1477.  1500 byte packets with DF set would not pass.
Removing the secondaries fixed the problem.
Anyone seen this before?