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New Member

High CPU - IP Input


Having a problem with traffic causing high CPU on 7204VXR (NPE400):

#sho processes cpu sorted

CPU utilization for five seconds: 48%/14%; one minute: 46%; five minutes: 26%

PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process

72 2516700 15388329 163 32.76% 30.20% 16.10% 0 IP Input

42 47220 6815700 6 0.32% 0.32% 0.32% 0 Per-Second Jobs

cef is enbabled on all FE Ints.


interface FastEthernet2/0

description Crossover to ERT01-BNE

ip address

ip route-cache same-interface

ip route-cache flow

ip ospf message-digest-key 10 md5 XXXXX

duplex full

mpls ip

service-policy output MPLS-EGRESS


#show ip interface fastEthernet 2/0

FastEthernet2/0 is up, line protocol is up

Internet address is

Broadcast address is

Address determined by non-volatile memory

MTU is 1500 bytes

Helper address is not set

Directed broadcast forwarding is disabled

Multicast reserved groups joined:

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 fast switching on the same interface is enabled

IP Flow switching is enabled

IP CEF switching is enabled

IP Flow switching turbo vector

IP Flow CEF switching turbo vector

IP multicast fast switching is enabled

IP multicast distributed fast switching is disabled

IP route-cache flags are Fast, Flow cache, CEF, Full Flow

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

Policy routing is disabled

Network address translation is disabled

BGP Policy Mapping is disabled

WCCP Redirect outbound is disabled

WCCP Redirect inbound is disabled

WCCP Redirect exclude is disabled

Just wondering what else I can check to further diagnose?


Re: High CPU - IP Input


Since CEF is enabled on all the interfaces, the cause has to be packets destined for the router itself. Do you run BGP on this router ? And if so, how many BGP sessions are configured ?


New Member

Re: High CPU - IP Input

Only iBGP for MPLS - Further diagnoses has revealed that it is only caused by traffic that is ingress to the router, and also terminates on the router - i.e. I have an L2TPv3 tunnel setup (Which terminates on Loopback on the router), traffic ingress to this router causes the CPU to go beserk(Which makes sense as the router has to deal with it....i.e. it cannot forward anywhere) - If I pump data in the other direction, the router terminating the other side of the tunnel CPU is hit hard.


Re: High CPU - IP Input

So how much traffic are you hitting the router with when you see such high CPU ? And what sort of NPE card are you using ?


New Member

Re: High CPU - IP Input

NPE400 - I can cause high cpu by grabbing a 500Mb file (Over a 16Mb link).

If traffic is going "through" the routers, there is no CPU problems (So it appears as though it is being caused because the L2TPv3 tunnel terminates on the Routers (Loop Ints)

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