HSRP active on both routers

[Umesh Shetty]

    Hi All,

I have been troubleshooting an issue where the HSRP on both the primary and secondary core switch is active. These two hsrp interfaces are connected through a distribution layer 2 switches. I tried to debug on the secondary router and could only see hsrp packets being sent out not received. Then i tried to capture packets on the distribution switches to check if they are forwarding these packets. The distribution switch is receiving the HSRP packet from the core switch 1 it is sending the packet to the secondary distribution switch but the secondary distribution switch is not forwarding the packet to the secondary core switch. Here is the hardware models used.

Core Switch 1 & 2 - WS-C3750G-24TS

Distribution Switch 1 & 2 -

WS-C3750G-24TS

WS-C3750G-12S

Connectivity is as shown below.

[Reza Sharifi]

Hi,

Can you post configs from both HSRP core switches?

also post 'sh hsrp group xx" output from both switches.

[siddhartham]

Is the Link (g1/0/28) between the core switches is a layer-3 link?

Siddhartha

[akinmafes]

Check the vlans on the switch if the device is in the required vlan and if the vlan is created on both switches if the vtp mode is transparent.

Sent from Cisco Technical Support iPad App

[Umesh Shetty]

Hi Friends,

Sorry for not being able to reply to your queries. Was actually busy all this time trying to troubleshoot this issue. Here are the steps we did.

1> We are able to ping the HSRP peer ip addresses which meanth that there was no Layer 2 connectivity issue.

2>  Next we configured the links between the core router and the distribition switch as a trunk and created a SVI interface for that Vlan on the core and run HSRP on them. Still the same result pings were successsful but HSRP not forming.

3> Then to completely isolate the distribution switch we added another link between the two core switches as configured it as trunk to allow only that Vlan. Still the same result pings were successsful but HSRP not forming.

4> We did a packet capture on the trunk link on the secondary core switch then to see if packets are reaching from the opposite router.

5> The sniffer captures showed that the packets are coming but for some reason are not being processed.

6> We did a debug standby packets , strangely the debugs only showed packets coming from the other core switch were not seen in the debug output.

7> The two results ie the sniffer capture and the debug output showed weird outputs and Cisco considered it abnormal for the router not to show the packets that are actually hitting the router in the debug output.

8> We then decided to reload the secondary router and it crashed, it would boot and when it tried to initialize the flash it would say that its unable to read flash.

9> TAC then suggested that this is a hardware issue a hadrware replacement is the required.

10> We received the device within 4 hours and both core switches were replaced and the HSRP worked well on both.

Thanks

Umesh