[c-nsp] Strange new PIM Tunnel interfaces after upgrade to 12.2(33)SRC

[John Neiberger]

We recently upgraded several 7600s from 12.2(18) to 12.2(33)SRC. After
the upgrade, we noticed several new tunnel interfaces. According to
the output of "show int tunnel1", as an example, this is a
transmit-only PIM tunnel between that router and a 4948 in another
data center. We have absolutely no idea what these tunnel interfaces
are being used for or how (or why!) they're dynamically created.

Do any of you have any idea what these are?

Tunnel1 is up, line protocol is up
  Hardware is Tunnel
  Interface is unnumbered. Using address of TenGigabitEthernet4/4 (10.1.1.2)
  MTU 17912 bytes, BW 100 Kbit/sec, DLY 50000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation TUNNEL, loopback not set
  Keepalive not set
  Tunnel source 10.1.1.2 (TenGigabitEthernet4/4), destination 10.3.4.1
   Tunnel Subblocks:
      src-track:
         Tunnel1 source tracking subblock associated with TenGigabitEthernet4/4
          Set of tunnels with source TenGigabitEthernet4/4, 4 members
(includes iterators), on interface <OK>
  Tunnel protocol/transport PIM/IPv4
  Tunnel TOS/Traffic Class 0xC0,  Tunnel TTL 255
  Tunnel transport MTU 1472 bytes
  Tunnel is transmit only
  Tunnel transmit bandwidth 8000 (kbps)
  Tunnel receive bandwidth 8000 (kbps)
  Last input never, output never, output hang never
  Last clearing of "show interface" counters 3w0d
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/0 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
  L2 Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes
  L3 in Switched: ucast: 0 pkt, 0 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 0 pkt, 0 bytes mcast: 0 pkt, 0 bytes
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     0 packets output, 0 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out