Jumbo MTU issue on the FWSM

Guys,

Just came across something weird which I cant make out and a few searches
haven't returned any meaningful results either. Guessing someone out here
might be of help please.

I am trying to configure jumbo MTU on my network. All other parts of the
network are doing jumbo frames successfully but my FWSM (outside). The FWSM
outside interface keeps fragmenting my IP packets (despite the configured
large MTU on all its interfaces). This made me suspect the host 6509 doing
something rather unpleasant. All IP and L2 interfaces are in fact configured
with the right MTU size.

So I came across a mismatch (from "show vlan mtu" output), see below. I then
did a "show spanning-tree vlan 17" to find out an arbitrary port-channel
interfaces in my spanning tree domain, which are neither configured nor
accessible from any part of the host 6509 configuration. It appears that
these arbitrary interfaces have a lower MTU, which might be responsible for
the misbehavior I am seeing.

Can someone please tell me what these do and if they are infact
configurable?

Thanks as usual!

Sadiq

###################################################################

Please see below:

R601#
R601#
R601#sh span vlan 17

VLAN0017
  Spanning tree enabled protocol rstp
  Root ID Priority 24593
             Address 0005.5f91.d800
             This bridge is the root
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

  Bridge ID Priority 24593 (priority 24576 sys-id-ext 17)
             Address 0005.5f91.d800
             Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
             Aging Time 480

Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- --------
--------------------------------
Te9/3 Desg FWD 2 128.1027 P2p
Po306 Desg FWD 3 128.1666 P2p Edge
Po310 Desg FWD 3 128.1667 P2p Edge
Po311 Desg FWD 3 128.1668 P2p Edge

R601#
R601#sh vlan mtu

VLAN SVI_MTU MinMTU(port) MaxMTU(port) MTU_Mismatch
---- ------------- ------------- ------------ ------------
1 1500 1500 (Gi3/1 ) 9000 (Te9/3 ) Yes

.....

17 8500(TooBig) 1500 (Po306 ) 9000 (Te9/3 ) Yes
18 - 1500 (Po306 ) 9000 (Te9/3 ) Yes
19 - 1500 (Po306 ) 9000 (Te9/3 ) Yes

.....

R601#
R601#
R601#
R601#show mod
R601#show mod
Mod Ports Card Type Model Serial
No.
--- ----- -------------------------------------- ------------------
-----------
  1 6 Firewall Module WS-SVC-FWM-1
SAD080803FL
  2 6 Firewall Module WS-SVC-FWM-1
SAD102105VN
  3 48 CEF720 48 port 10/100/1000mb Ethernet WS-X6748-GE-TX
SAL1106GBZ6
  4 16 SFM-capable 16 port 1000mb GBIC WS-X6516-GBIC
SAD0541041G
  5 2 Supervisor Engine 720 (Active) WS-SUP720-3BXL
SAL1103E6YD
  6 6 Firewall Module WS-SVC-FWM-1
SAD07170252
  7 6 Firewall Module WS-SVC-FWM-1
SAD071202GX
  8 4 CEF720 4 port 10-Gigabit Ethernet WS-X6704-10GE
SAL114998VQ
  9 8 CEF720 8 port 10GE with DFC WS-X6708-10GE
SAL1215LWZC

Mod MAC addresses Hw Fw Sw
Status
--- ---------------------------------- ------ ------------ ------------
-------
  1 0003.feae.2b58 to 0003.feae.2b5f 3.0 7.2(1) 4.0(12)
ShutDown
  2 0017.95a3.e578 to 0017.95a3.e57f 4.0 7.2(1) 3.1(10)0 Ok
  3 001a.6c97.cb34 to 001a.6c97.cb63 2.5 12.2(14r)S5 12.2(33)SXI3 Ok
  4 00d0.c0d6.aba4 to 00d0.c0d6.abb3 3.0 6.1(3) 12.2(33)SXI3 Ok
  5 0017.9444.4c1c to 0017.9444.4c1f 5.3 8.4(2) 12.2(33)SXI3 Ok
  6 0002.fcbe.1634 to 0002.fcbe.163b 2.0 7.2(1) 3.1(10)0 Ok
  7 0003.feab.3462 to 0003.feab.3469 1.1 7.2(1) 3.1(10)0 Ok
  8 001c.585c.a368 to 001c.585c.a36b 2.6 12.2(14r)S5 12.2(33)SXI3 Ok
  9 001d.4577.ae18 to 001d.4577.ae1f 1.4 12.2(18r)S1 12.2(33)SXI3 Ok

Mod Sub-Module Model Serial Hw
Status
---- --------------------------- ------------------ ----------- -------
-------
  3 Centralized Forwarding Card WS-F6700-CFC SAL1103EL86 2.1 Ok
  5 Policy Feature Card 3 WS-F6K-PFC3BXL SAL1101D02A 1.8 Ok
  5 MSFC3 Daughterboard WS-SUP720 SAL1103E9E9 2.6 Ok
  8 Centralized Forwarding Card WS-F6700-CFC SAL11488UNG 4.0 Ok
  9 Distributed Forwarding Card WS-F6700-DFC3C SAL1215M317 1.0 Ok

Mod Online Diag Status
---- -------------------
  1 Pass
  2 Pass
  3 Pass
  4 Pass
  5 Pass
  6 Pass
  7 Pass
  8 Pass
  9 Pass

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