LARTC - Dec 2006 - (null) in ip route get

I''m seeing strange output with iproute 2.6.18 and 2.6.19 with ip route 
get. Instead of (null) I would expect to see sth like mtu. Does anyone 
have good explanation for it?

$  ip route get 123.45.67.1
123.45.67.1 via 10.32.0.254 dev eth0  src 10.32.0.193
     cache  (null) 1500 ssthresh 1460 advmss 64
-- 
Radek Vokál <rvokal@redhat.com>
Base OS Engineering - Team Lead

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