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WCCP Tunnel MTU size

We recently upgraded a Catalyst 6509 switch with a new Supervisor Module (WS-SUP2T-10G) running IOS vers. 12.2(50) SY3

After the upgrade we noticed an error using the WCCP protocol. The following log occurs everytime we enable the WCCP:

Nov 24 15:22:47.306: %TUN-4-MTUCONFIGEXCEEDSTRMTU_IPV4: Tunnel4 IPv4 MTU configured 17760 exceeds tunnel transport MTU 1476

Nov 24 15:22:47.306: %WCCP-5-SERVICEFOUND: Service 10 acquired on WCCP Client

This is the show tunnel inteface output:

Tunnel4 is up, line protocol is up

  Hardware is Tunnel

  Interface is unnumbered. Using address of Tunnel5 (

  MTU 17864 bytes, BW 100 Kbit, DLY 50000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation TUNNEL, loopback not set

  Keepalive not set

  Tunnel source

  Tunnel protocol/transport multi-GRE/IP

    Key disabled, sequencing disabled

    Checksumming of packets disabled

  Tunnel TTL 255, Fast tunneling enabled

  Tunnel transport MTU 1472 bytes

  Last input never, output never, output hang never

  Last clearing of "show interface" counters never

  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

     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 output buffer failures, 0 output buffers swapped out

This error is the cause of a buoncing behaviour on the internet connection using a Proxy configured with the WCCP and GRE protocol.

The tunnel interface is obviously not modifiable due to the fact that is created only when the WCCP is started so no modification can be made on the MTU size.

Can someone help me on this?

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