[c-nsp] FIB insertion issues on Sup2T routers

["Rolf Hanßen"]

Hello,

I had 3 incidents within a week in which Sup2T-XL routers switched to
software forwarding.

I.e. log says:
%MLSCEF-4-FIB_TCAM_INSERT_FAIL: FIB entry insertion into tcam failed, one
IPv4 route may be absent from hardware table

Was fixed by a reboot in each case.

Uptime differs (several weeks up to years), chassis differ (6509E/7609S),
all routers run 15.1(2)SY1.

Number of total routes is not close to the edge:

#sh platform hardware cef summary
Total routes:                     709683
    IPv4 unicast routes:          664027
        IPv4 non-vrf routes:      664027
        IPv4 vrf routes:          0
    IPv4 multicast routes:        3
    IPv6 unicast routes:          45650
        IPv6 global routes:       45649
            IPv6 non-vrf routes:  45649
            IPv6 vrf routes:      0
        IPv6 link-local routes:   1
    IPv6 multicast routes:        1
    mpls routes:                  1
    mpls-vpn routes:              0
    eompls-l2 routes:             1
    eom-ipv4-mcast routes:        0
    eom-ipv6-mcast routes:        0

#sh platform hardware cef maximum-routes

 Fib-size: 1024k (1048576),     shared-size: 1016k (1040384),
shared-usage: 735k(753326)

 Protocol         Max-routes     Use-shared-region  Dedicated
 --------         ----------     -----------------  ---------
 IPV4             1017k           Yes                1k
 IPV4-MCAST       1017k           Yes                1k
 IPV6             1017k           Yes                1k
 IPV6-MCAST       1017k           Yes                1k
 MPLS             1017k           Yes                1k
 EoMPLS           1017k           Yes                1k
 VPLS-IPV4-MCAST  1017k           Yes                1k
 VPLS-IPV6-MCAST  1017k           Yes                1k

They did not have that issue the same time and receive the same routes
that also other Sup2T routers (that did not have that issue) receive, so I
do not expect this to be result of a short wave of routes learned from
peers/uplinks.

Did anyone else have that issue?
Any hints how to find the cause (without support contract)?

kind regards
Rolf