Slow InterVlan Routing Cisco 3560x

[Jarrett Cadiz]

Hi Everyone,

I have been learning a lot about Cisco switches and I had one setup with a few vlans (10,20,70). Recently I enabled inter-vlan routing on the switch and everything seemed to be going ok, and then suddenly file transfer rates between computers on one vlan to another became less than 3MB/s. However file transfers between any computer on the same vlan were around 100-120MB/s. I do have STP running on this switch and two other SG-300-28P switches, but I don't think that is the problem but I may be wrong. The Cisco 3560x is configured as the root bridges and it is running in r-pvst, and the other two SG-300-28P are running in rstp.

Some configuration snippets:

service timestamps debug datetime msec

service timestamps log datetime msec

service password-encryption

!

hostname GBe1

!

boot-start-marker

boot-end-marker

!

!

no aaa new-model

system mtu routing 9000

authentication mac-move permit

ip routing

spanning-tree mode rapid-pvst

spanning-tree loopguard default

spanning-tree extend system-id

spanning-tree vlan 1,10,20,70 priority 24576

spanning-tree vlan 1,10,20,70 forward-time 12

spanning-tree vlan 1,10,20,70 max-age 16

!

!

!

!

vlan internal allocation policy ascending

!

!

!

interface Port-channel1

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

!

interface Port-channel2

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

!

interface GigabitEthernet0/1

switchport access vlan 10

switchport mode access

switchport nonegotiate

!

interface GigabitEthernet0/11

switchport access vlan 20

switchport mode access

switchport nonegotiate

!

interface GigabitEthernet0/14

switchport access vlan 70

switchport mode access

switchport nonegotiate

!

interface GigabitEthernet0/39

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 1 mode active

!

interface GigabitEthernet0/40

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 1 mode active

!

interface GigabitEthernet0/41

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 1 mode active

!

interface GigabitEthernet0/42

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 1 mode active

!

interface GigabitEthernet0/43

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 2 mode active

!

interface GigabitEthernet0/44

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 2 mode active

!

interface GigabitEthernet0/45

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 2 mode active

!

interface GigabitEthernet0/46

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,10,20,70

switchport mode trunk

switchport nonegotiate

channel-protocol lacp

channel-group 2 mode active

!

interface Vlan1

no ip address

spanning-tree link-type point-to-point

!

interface Vlan20

ip address 10.7.7.2 255.255.255.0

spanning-tree link-type point-to-point

!

interface Vlan70

ip address 10.7.12.2 255.255.255.0

spanning-tree link-type point-to-point

!

interface Vlan10

ip address 10.7.5.2 255.255.255.0

spanning-tree link-type point-to-point

!

ip http server

ip http secure-server

!

ip route 0.0.0.0 0.0.0.0 10.7.7.70

!

ip sla enable reaction-alerts

logging esm config

Thank you for your help in advance.

Thanks!

[Dan-Ciprian Cicioiu · Accepted solution]

Hi ,

I would try:

system mtu routing 1504

Dan

[glen.grant · Accepted solution]

I agree I would   try changing themtu back to 1500 .  If a device is using 9000 byte packets and you are transfering between vlans everything gets fragmented because  these models cannot  route jumbo frames .  This is a platform restriction.

[Jarrett Cadiz]

Hi Dan and Glen,

Thank you so much for replying to me. I did change the routing mtu back to default, however with it only switching I still found it going much slower than wire speed.

It later was discovered that a downstream switch (esw-540-24p) does not support Jumbo or hasn't been enabled and that was causing hiccups. With the esw-540-24p removed and routing mtu back to default, performance is now amazing on the switch once again.

Thanks you so much for your help!