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New Member

Ping drops when CE has no default-gateway.

Hi,

Just interested if anyone has seen ping dropouts when the CE can't see its default-gateway.

Setup:

CE 10.1.1.1/24

PC 10.1.1.2/24

Router 10.1.1.254/24

The CE is setup with the default-gateway of 10.1.1.254.

When the router is on the network, the PC can run a continous ping to CE with 100% success. But as soon as I disconnect the router from the network, the continous ping from the PC, starts a ping pattern of 4 success and 2 fails, this would just repeat. And when the router is re-connected, all the pings are successful again.

Another interesting thing is, the results from the command 'show ip route' on the CE is different

before and after the df-gw is disconnected.

The CE is 565 running 5.3.5b8 code.

Your thoughts?

Cheers,

Jason.

4 REPLIES
Cisco Employee

Re: Ping drops when CE has no default-gateway.

capture a sniffer trace to see what is going on.

Do not sniff on the pc itself so.

Capture the port on which the CE is attached to or capture a tcpdump on the CE itself.

Capture arp and icmp traffic.

G.

New Member

Re: Ping drops when CE has no default-gateway.

Thanks for your response.

I figure you would ask me this...

I'll try to organise it mid next week.

At one point I change the IP address on the router and did a debug IP ICMP and didn't see anything interesting..

Thanks.

Jason.

New Member

Re: Ping drops when CE has no default-gateway.

Setup:

9.190.32.202/27 - PC

9.190.32.203/27 - Content Engine

9.190.32.193/27 - default gateway (router)

All devices are on the same subnet. PC is running a continous ping to CE from a DOS prompt. The ping would work 100% if the default gateway is connected to the network. But if I disconnect the default gateway from the network, then 2 of 7 ping packet would timeout and this would be repeat.

ie

ping response

ping response

ping response

time-out

time-out

ping response

ping response

ping response

time-out

time-out

ping response

.

,

ping-not-working-ce.cap contains a ethereal capture of the CE not responding to local ping packets, when the default gateway is not available.

From the trace, it shows that the CE (9.190.32.203) is continuiously sending ARP request looking for the default gateway (9.190.32.193) and not the PC (9.190.32.202), even though the PC is sending the ping request. Also, even after the PC responds to the ARP request with its MAC address, the CE would respond to 3 ping packets, then tries to send ARP request default gateway (9.190.32.193) again.

As soon as you plug the default gateway onto the network, the CE responds 100%.

Cisco Employee

Re: Ping drops when CE has no default-gateway.

that's weird.

I would suggest to do a restore-factory-default and reconfigure the CE.

Only configure ip and default gateway and verify if the problem is still there.

If so, open a case with the TAC as this needs to be investigated more.

Thanks,

Gilles.

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