[c-nsp] 7513 - RSP4 - 122-25.S15 - MLPPP / Dcef Weirdness

[Gregory Boehnlein]

Hello,
	Over the weekend, we updated one of our 7513s from 12.2.25S12 to the
12.2.25S15. The driver behind this was service policies used for LLQ
dropping from interfaces, causing all sorts of havoc w/ our voice
prioritization. The thought was that moving to the more current issue would
address this. It did not.

We also noticed something else odd. We have three multilink bundles on this
router, and have had them configured to use "ip route-cache distributed" for
over a year. We haven't had any problems w/ this until rebooting into the
S15 image. Of the three bundles, Mu1 is the only one that seems to work w/
dcef. Mu2 and Mu3 have had to be set w/ CEF disabled to route properly. The
symptoms are that from the router you can ping the other sides of Mu2 and
Mu3, but no external routing is possible. The interface stats show packets
being dropped on the output buffer.. which is weird, until we disable CEF
for those interfaces.. then everything starts working properly, and the
stats show Processor Switching.

Am I missing something? Or is there an issue w/ S15 / Dcef / Multilink and
IP Unnumbered to a loopback?

core-ar1#show interfaces mu1 stats
Multilink1
             Switch path    Pkts In   Chars In   Pkts Out  Chars Out
               Processor          0          0          0          0
             Route cache     377309  104869674          0          0
       Distributed cache          0          0     459932  500579863
                   Total     377309  104869674     459932  500579863
core-ar1#show interfaces mu2 stats
Multilink2
             Switch path    Pkts In   Chars In   Pkts Out  Chars Out
               Processor        212      12247    1339852  487984693
             Route cache    1837532 2064076461          0          0
       Distributed cache          0          0          0          0
                   Total    1837744 2064088708    1339852  487984693
core-ar1#show interfaces mu3 stats
Multilink3
             Switch path    Pkts In   Chars In   Pkts Out  Chars Out
               Processor         18       1640    1068371 1264449182
             Route cache     701359   67160511          0          0
       Distributed cache          0          0          0          0
                   Total     701377   67162151    1068371 1264449182

interface Multilink1
ip unnumbered Loopback0
 no cdp enable
 ppp multilink
 ppp multilink interleave
 multilink max-links 2
 multilink min-links 1
 multilink load-threshold 1 either
 no ppp multilink fragmentation
 multilink-group 1
 no clns route-cache
end

interface Multilink2
ip unnumbered Loopback0
 no cdp enable
 ppp multilink
 ppp multilink interleave
 multilink max-links 3
 multilink min-links 1
 multilink load-threshold 1 either
 no ppp multilink fragmentation
 multilink-group 2
 no clns route-cache
end

interface Multilink3
ip unnumbered Loopback0
 no cdp enable
 ppp multilink
 ppp multilink interleave
 multilink max-links 2
 multilink min-links 1
 multilink load-threshold 1 either
 no ppp multilink fragmentation
 multilink-group 3
 no clns route-cache
end