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3750: High CPU After Enabling HSRP


I am wondering why our 3750's CPU process increased above 90% after enabling HSRP. It used to be a single SVI until it was converted to HSRP. Can you please help me identify the problem? Thanks in advance.



Re: 3750: High CPU After Enabling HSRP

This typically happens when route is not known on the switch resulting in packets punted to CPU.

Can you paste

1-HSRP Config

2-show standby

3-show ip route.

Are you using SDM ?


Re: 3750: High CPU After Enabling HSRP

interface Vlan50

description access switch management

ip address

ip pim sparse-dense-mode

standby 50 ip

standby 50 timers msec 500 msec 1500

standby 50 preempt delay minimum 120


sjo2-3750G#sh standby vlan 50

Vlan50 - Group 50

State is Active

2 state changes, last state change 1d10h

Virtual IP address is

Active virtual MAC address is 0000.0c07.ac32

Local virtual MAC address is 0000.0c07.ac32 (v1 default)

Hello time 500 msec, hold time 1500 msec

Next hello sent in 0.374 secs

Preemption enabled, delay min 120 secs

Active router is local

Standby router is, priority 72 (expires in 1.416 sec)

Priority 100 (default 100)

IP redundancy name is "hsrp-Vl50-50" (default)


sjo2-3750G#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route

Gateway of last resort is to network is subnetted, 1 subnets

C is directly connected, Vlan20 is variably subnetted, 10 subnets, 6 masks

C is directly connected, Vlan51

C is directly connected, Loopback0

S is directly connected, Null0

C is directly connected, Vlan55

C is directly connected, Vlan50

C is directly connected, Vlan52

C is directly connected, Vlan10

C is directly connected, Vlan53

C is directly connected, Vlan54

C is directly connected, Vlan1

B* [170/0] via, 2w6d


We are just using the default SDM template.

Re: 3750: High CPU After Enabling HSRP

are you using this command "sdm prefer routing" or "sdm prefer vlan" ?

Re: 3750: High CPU After Enabling HSRP

The CPU is below 20% when we were still not using HSRP. This one is the highest process right now.

70 106474785 689475590 154 63.89% 63.65% 63.25% 0 HLFM address lea

I' reading this right now but cannot find the answer.


Re: 3750: High CPU After Enabling HSRP

sjo2-3750G#sh sdm prefer

The current template is "desktop default" template.

The selected template optimizes the resources in

the switch to support this level of features for

8 routed interfaces and 1024 VLANs.

number of unicast mac addresses: 6K

number of IPv4 IGMP groups + multicast routes: 1K

number of IPv4 unicast routes: 8K

number of directly-connected IPv4 hosts: 6K

number of indirect IPv4 routes: 2K

number of IPv4 policy based routing aces: 0

number of IPv4/MAC qos aces: 0.5K

number of IPv4/MAC security aces: 1K


We are using desktop default.

Re: 3750: High CPU After Enabling HSRP

It seems like "sdm prefer routing" might allocate some resources switch woudl need. I have not tested it myself so cannot guarantee it will fix ur issue.


Re: 3750: High CPU After Enabling HSRP

Thank you sir. Hopefully I can find what the real issue is.