02-12-2008 05:49 PM - edited 03-03-2019 08:40 PM
I have a 3560 switch which has CEF enabled on all routed interfaces. Output from show ip interfaces shows the following:
IP fast switching is enabled
IP CEF switching is enabled
IP CEF switching turbo vector
IP multicast fast switching is enabled
IP multicast distributed fast switching is enabled
IP route-cache flags are Fast, CEF
for Vlan3, Fa0/11, Fa0/24.
However, a show interface stats shows all packets being switched by the processor, zero by the Route cache. My understanding is that CEF and fast-switched packets should show up here. I also see a relatively high utilization on CPU on the IP input process. For example, I see this:
Vlan3
Switch path Pkts In Chars In Pkts Out Chars Out
Processor 8032 544231 5958 777174
Route cache 0 0 0 0
Total 8032 544231 5958 777174
Applicable portions of my current config:
!
version 12.2
no service pad
!
no aaa new-model
ip subnet-zero
ip routing
no ip domain-lookup
!
ip multicast-routing distributed
!
!
!
!
!
no file verify auto
spanning-tree mode pvst
spanning-tree extend system-id
!
vlan internal allocation policy ascending
!
!
interface FastEthernet0/2
switchport access vlan 3
!
interface FastEthernet0/4
switchport access vlan 3
duplex full
!
interface FastEthernet0/5
switchport access vlan 3
!
interface FastEthernet0/6
switchport access vlan 3
speed 100
no cdp enable
!
interface FastEthernet0/7
switchport access vlan 3
duplex full
!
interface FastEthernet0/11
no switchport
ip address 1.2.3.4 255.255.255.0
!
interface FastEthernet0/24
no switchport
ip address 5.6.7.8 255.255.255.0
ip pim sparse-mode
duplex full
speed 100
!
interface Vlan3
description Order Subnet and Unicast
ip address 9.10.11.12 255.255.255.0 secondary
ip address 13.14.15.16 255.255.255.0
ip pim sparse-mode
!
!
end
I initially concentrated on the multicast portion, since that's the majority of my data, but realized that no packets, not even TCP, were being fast- or CEF switched. Any suggestions would be appreciated.
02-12-2008 07:43 PM
Hi
Just remembering read somewhere that "locally originated traffics are processes switched"..
but ur case u are mentioning that packets are getting traverse across the switch..???
lets see what experts says..
arun
02-12-2008 11:44 PM
Hi,
Fast Switching is a feature that rely on (Route-Cache). On routers when you enable (Ip route-cache) per interface , its just stores the recent routes used by the router for fast Switching process.
In a Multicast environment, it has the same logic, If you want to enable it, you should configure (IP mroute-cahe) for any pim interface enabled.
verify: (sh ip mroute-cache) after configuring it.
HTH
Mohamed
02-13-2008 03:34 AM
Try enabling Route-Cache on each interface that you are running (ip route-cache). This will start the cache switching on the interfaces...
02-13-2008 05:51 AM
Thanks for the responses. As you've seen from my initial output, ip route-cache is already enabled (it's enabled by default so you don't see it in the config), and ip mroute-cache distributed is also enabled on all interfaces. ip mroute-cache distributed is automatically enabled when you enable ip pim *. The only time you'd see ip route-cache or ip mroute-cache in this config is if it were preceded by a "no".
02-14-2008 06:42 AM
The reason CEF packets weren't showing in "show interface stats" is that they are not included in "Route Cache" output on switch platforms. You can use "ip cef accounting per-prefix" and then "show adjacencies" to see CEF hit counts. In fact, we were not process switching most packets.
02-14-2008 12:13 PM
Hi,
Fine if you solved it, but have point to add:
You said you are not process switching any packet, while at your previous post you also mentioned it's enabled. u are process switching here since you dont manually disabled (mroute-Cache) per the interface.
Its clear from the config output that both (Fast Switching) & (CEF) are operational.
HTH
Mohamed
02-14-2008 02:17 PM
This is normal. The 3750 doesn't keep statistics for "Distributed Cache", which is what is handling nearly all of these packets.
As long as your CPU stays down, you can be assured the box is doing its job.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide