Hi,
4500 configured as layer 2 switch.
I am testing a cisco WS-C4948-10GE in the lab.
I have found a unique "feature" of the switch where frames are re-ordered only when the following conditions are met:
1. The frames are of an unknown format (ie not IP)
2. The frames have the same source MAC address but different destination MAC address. And are sent interleaved. Destination A, B, A, B etc.
3. The frames of the two streams are of the same length but incrementing. 64,64,65,65....1510,1510,64,64,...etc.
4. The switch has learnt the MAC address
When the frames lengths wrap around the sequence 1510,1510,64,64,65,65 is reordered to 1510,64,1510,64,65,65
If the protocol is IP then the problem goes away.
If the MAC addresses are unknown then the problem goes away.
If the length limits are closer then the problem goes away.
I have looked at the switch architecture and I can only assue that the two frames are pushed into seperate Tx queues somehow when the conditions above are not met.
Relevant config;
version 12.2
boot system flash bootflash:cat4500-ipbase-mz.122-31.SGA.bin
boot system flash bootflash:cat4000-i5s-mz.122-25.EWA10.bin
no qos rewrite ip dscp
qos map dscp 0 1 2 3 4 5 6 7 to tx-queue 3
qos map dscp 8 9 10 11 12 13 14 15 to tx-queue 3
qos map dscp 16 17 18 19 20 21 22 23 to tx-queue 3
qos map dscp 24 25 26 27 28 29 30 31 to tx-queue 3
qos map dscp 48 49 50 51 52 53 54 55 to tx-queue 3
qos map dscp 56 57 58 59 60 61 62 63 to tx-queue 3
qos map dscp 8 9 10 11 12 13 14 15 to cos 0
qos map dscp 16 17 18 19 20 21 22 23 to cos 0
qos map dscp 24 25 26 27 28 29 30 31 to cos 0
qos map dscp 32 33 34 35 36 37 38 39 to cos 0
qos map dscp 40 41 42 43 44 45 46 47 to cos 0
qos map dscp 48 49 50 51 52 53 54 55 to cos 0
qos map dscp 56 57 58 59 60 61 62 63 to cos 0
qos map cos 1 2 3 4 5 6 7 to dscp 0
vtp interface default
no errdisable detect cause pagp-flap
no errdisable detect cause dtp-flap
no errdisable detect cause link-flap
no errdisable detect cause l2ptguard
no errdisable detect cause gbic-invalid
no errdisable detect cause dhcp-rate-limit
no errdisable detect cause arp-inspection
errdisable recovery interval 30
!
no spanning-tree vlan 100,126,999-1001,2000-2001
system mtu 1552
interface GigabitEthernet1/23
switchport trunk encapsulation dot1q
switchport trunk native vlan 999
no switchport trunk native vlan tag
switchport trunk allowed vlan 999,1001,2001
switchport mode trunk
switchport nonegotiate
qos trust cos
udld port aggressive
no cdp enable
!
interface GigabitEthernet1/24
switchport trunk encapsulation dot1q
switchport trunk native vlan 999
no switchport trunk native vlan tag
switchport trunk allowed vlan 999,1001,2001
switchport mode trunk
switchport nonegotiate
qos trust cos
no cdp enable
!
interface GigabitEthernet1/25
switchport trunk encapsulation dot1q
switchport trunk native vlan 999
no switchport trunk native vlan tag
switchport trunk allowed vlan 999,1001,2001
switchport mode trunk
switchport nonegotiate
qos trust cos
no cdp enable
!
monitor session 1 source interface Gi1/23 rx
monitor session 1 destination interface Gi1/25 encapsulation dot1q ingress vlan 999
