12-15-2005 11:08 PM - edited 03-03-2019 01:09 AM
Hi
Since we installed the new network we have on our 6500 Giant Frames on the Trunkports(dot1q)and rapid spanning tree to the access-switches. All Accessswitches are running without problems and errors. Also on the Etherchannel between the 2 6500 i have Giant frames. Has anyone an idea? I tried to set the MTU size on the Etherchannel (2 tengigabit) to 9216
on the accesswitches i have MTU 1500
Here is a sh int from a gig port
GigabitEthernet2/7 is up, line protocol is up (connected)
Hardware is C6k 1000Mb 802.3, address is 0015.6251.70de (bia 0015.6251.70de)
Description: to lwnsw150102
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Full-duplex, 1000Mb/s, media type is LH
input flow-control is off, output flow-control is off
Clock mode is auto
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:27, output 00:00:04, output hang never
Last clearing of "show interface" counters 1d20h
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 88000 bits/sec, 26 packets/sec
5 minute output rate 347000 bits/sec, 71 packets/sec
8775949 packets input, 3527532905 bytes, 0 no buffer
Received 22299 broadcasts, 0 runts, 1188766 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
14590096 packets output, 10194273662 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
Bernhard
12-16-2005 02:13 AM
Hi Bernhard,
giants are frames that are discarded because they are larger than 1518 Bytes. You interface has a mtu of 1500 Byte so 1518 is the max ethernet frame it will handle.
Do you have a "mtu 9216" also on this interface? That should fix it.
The second question would be where the giants are caused. Without interface config this is hard to tell.
Martin
12-16-2005 02:27 AM
Hi Martin
This is the Config of the Portchannel of the Tengig interfaces
interface Port-channel1
mtu 9216
bandwidth 10000000
no ip address
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
!
interface TenGigabitEthernet1/1
mtu 9216
bandwidth 10000000
no ip address
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode desirable
!
interface TenGigabitEthernet1/2
mtu 9216
bandwidth 10000000
no ip address
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode desirable
And on the Accessswitches i have this configs
interface GigabitEthernet2/4
description to xxx
no ip address
switchport
switchport trunk encapsulation dot1q
switchport mode trunk
Should i configure mtu 9216 or mtu 1518 on the gigabit trunk interfaces to the accessswitches?
Bernhard
12-16-2005 02:34 AM
Hello Bernhard,
I think your giants are caused by 802.1Q frames, which use an additional 4 bytes, making the total 1522 bytes. These are called baby-giant frames. I would think setting the MTU to 1504 (which then would total 1522) should be sufficient...
HTH,
GP
12-16-2005 03:03 AM
Hello GP
Should I set the MTU 1504 on the access or the coreswitch Interfaces?
Bernhard
12-16-2005 03:38 AM
Hello Bernhard,
you need to set the MTU to 1504 on all trunking ports on both the access and the core switches, that is, all ports configured with 802.1Q.
Regards,
GP
12-16-2005 06:18 AM
What kind of module is this and what version of IOS are you running? Also, take a look at the following cosmetic bug if it is a 6724 or 6748 card.
http://www.cisco.com/cgi-bin/bugtool/onebug.pl?bugid=CSCef87392
12-18-2005 07:06 AM
Its the WS-X6748-SFP module and i run the IOS Version 12.2(17d)SXB9 on the switches. Would u recommend us to update the IOS to a newer version, and what version u would choose?
12-18-2005 07:30 AM
This bug was fixed in 12.2(17d)SXB11. So I would stick with this unless you need features of newer releases. Do read the release notes for known issues before you decide on which release you want to upgrade to
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/ol_4164.htm
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