[c-nsp] Slow Inter-Vlan traffic

[Sébastien MALHEIRO]

HHi,



We’re having some issues with inter-vlan traffic going pretty slow on
6504-E chassis working in VSS (VS-S720-10G / WS-X6748-GE-TX), running IOS
version 12.2(33)SXH5.



Here’s the thing :

We have added 2 new Vlans on the swtichs (Vlan 41 : Production / Vlan 95 :
Admin).

Our customer told us that things are going pretty slow on both vlans (we
have seen 1.5Mbits/s of maximum bandwidth on Vlan 41).



Looking forward we saw that there is no distributed cache traffic on the
SVIs :



#sh interfaces Vlan41 stats

Vlan41

          Switching path    Pkts In   Chars In   Pkts Out  Chars Out

               Processor      64954    4280562     155332    9976305

             Route cache    6116040  589593156    8427463 10028760624

       Distributed cache          0          0          0          0

                   Total    6180994  593873718    8582795 10038736929



#sh interfaces Vlan95 stats

Vlan95

          Switching path    Pkts In   Chars In   Pkts Out  Chars Out

               Processor     732380   46887018    2009253  128644656

             Route cache    8377033 4951406934    5756730  480387249

       Distributed cache          0          0          0          0

                   Total    9109413 4998293952    7765983  609031905



On older (working well) SVIs added on the switchs we saw that packets are
going to distributed cache.

I’m not a expert on this but as far as I understand I can see that our
linecards are working in acef mode and that cef is enabled on the 2 new
SVIs (the sh cef interface output is the same on all the SVIs configured on
the switchs) :

#sh cef interface Vlan 41

Vlan41 is up (if_number 460)

  Corresponding hwidb fast_if_number 460

  Corresponding hwidb firstsw->if_number 460

  Internet address is X.X.X.X/X

  ICMP redirects are always sent

  IP unicast RPF check is disabled

  Output features: HW Shortcut Installation

  Inbound access list is not set

  Outbound access list is not set

  IP policy routing is disabled

  BGP based policy accounting on input is disabled

  BGP based policy accounting on output is disabled

  Hardware idb is Vlan41

  Fast switching type 22, interface type 147

  IP CEF switching enabled

  IP CEF switching turbo vector

  IP Null turbo vector

  IP prefix lookup IPv4 mtrie generic

  Input fast flags 0x0, Output fast flags 0x0

  ifindex 459(459)

  Slot unknown (-1) Slot unit 41 VC -1

  Transmit limit accumulator 0x0 (0x0)

  IP MTU 1500



#sh cef interface vlan 95

Vlan95 is up (if_number 455)

  Corresponding hwidb fast_if_number 455

  Corresponding hwidb firstsw->if_number 455

  Internet address is X.X.X.X/X

  ICMP redirects are always sent

  IP unicast RPF check is disabled

  Output features: HW Shortcut Installation

  Inbound access list is not set

  Outbound access list is not set

  IP policy routing is disabled

  BGP based policy accounting on input is disabled

  BGP based policy accounting on output is disabled

  Hardware idb is Vlan95

  Fast switching type 22, interface type 147

  IP CEF switching enabled

  IP CEF switching turbo vector

  IP Null turbo vector

  IP prefix lookup IPv4 mtrie generic

  Input fast flags 0x0, Output fast flags 0x0

  ifindex 454(454)

  Slot unknown (-1) Slot unit 95 VC -1

  Transmit limit accumulator 0x0 (0x0)

  IP MTU 1500



Moreover the “show ip cef vlan” output show that the good prefixes are
attached to the SVIs.

We also saw in the “show interface vlan” output that there are no “L3
in/out Switched” packets going through.



We would like to know where we could look to find the origin of this
problem.

Any Idea would be appreciated.



 Thanks.