October 14, 2008 12:05am pdt

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	[x] Attachment Details

High processor utilisation on Cisco 3750 stack

[x]

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7.8

Zones: Miscellaneous Networking, Domain Name Service (DNS), TCP/IP

Hi Experts,

I have an issue that I could do with some help on. I am working on a stack of 2 3750 switches, connected via their Stackwise interfaces. They in turn connect to 5 2950 switches via dual gigabit Ethernet links, configured as port channels. There are a number of VLANs which are configured such that half of the ports on the 2950s are in each VLAN, and the servers are configured on another VLAN to which the gigabit ports of the 3750s belong. Inter VLAN routing is configured to get the traffic between the VLANs.

I am experiencing high processor utilisation on the 3750s, mostly against the IP Input process. I have done some research and it seems that the switching algorithm may not be the most efficient. Attached is some show ip interface output to show how each VLAN is configured, and some output showing the process usage. I would appreciate any comments on improving the routing performance between VLANs - I am making the sweeping assumption in all this that the 3750s are capable of routing this amount of traffic without breaking a sweat when configured correctly.

CORESW#sh ip int
Vlan1 is up, line protocol is up
Internet protocol processing disabled
Vlan2 is up, line protocol is up
Internet address is x.x.x.x/24
Broadcast address is 255.255.255.255
Address determined by setup command
MTU is 1500 bytes
Helper address is not set
Directed broadcast forwarding is disabled
Multicast reserved groups joined: 224.0.0.10
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Local Proxy ARP is disabled
Security level is default
Split horizon is enabled
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are never sent
IP fast switching is enabled
IP CEF switching is enabled
IP CEF switching turbo vector
IP multicast fast switching is disabled
IP multicast distributed fast switching is disabled
IP route-cache flags are Fast, CEF
Router Discovery is disabled
IP output packet accounting is disabled
IP access violation accounting is disabled
TCP/IP header compression is disabled
RTP/IP header compression is disabled
Probe proxy name replies are disabled
Policy routing is disabled
Network address translation is enabled, interface in domain outside
WCCP Redirect outbound is disabled
WCCP Redirect inbound is disabled
WCCP Redirect exclude is disabled
BGP Policy Mapping is disabled
Input features: NAT Outside
Output features: Post-routing NAT Outside
Vlan3 is up, line protocol is up
Internet address is y.y.y.y/24
Broadcast address is 255.255.255.255
Address determined by setup command
MTU is 1500 bytes
Helper address is x.x.x.1
Directed broadcast forwarding is disabled
Multicast reserved groups joined: 224.0.0.10
Outgoing access list is not set
Inbound access list is not set
Proxy ARP is enabled
Local Proxy ARP is disabled
Security level is default
Split horizon is enabled
ICMP redirects are always sent
ICMP unreachables are always sent
ICMP mask replies are never sent
IP fast switching is enabled
IP CEF switching is enabled
IP CEF switching turbo vector
IP multicast fast switching is disabled
IP multicast distributed fast switching is disabled
IP route-cache flags are Fast, CEF
Router Discovery is disabled
IP output packet accounting is disabled
IP access violation accounting is disabled
TCP/IP header compression is disabled
RTP/IP header compression is disabled
Probe proxy name replies are disabled
Policy routing is disabled
Network address translation is enabled, interface in domain outside
WCCP Redirect outbound is disabled
WCCP Redirect inbound is disabled
WCCP Redirect exclude is disabled
BGP Policy Mapping is disabled
Input features: NAT Outside
Output features: Post-routing NAT Outside

Process output:

PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
-----------------------------------------------------------------------------------------------------
159 805309277 1180331872 682 44.65% 55.05% 49.99% 0 IP Input

Thanks in advance.

George

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