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New Member

Loss of first ping reply (C2950 - C3550)

When performing network checks, it seems that the first ping of aseries (of 5) is occasionally lost.

Is there any explanation to this behaviour, such as information timeouts etc... ?

Is there any setting to be done to avoid losing first pings ?

Thank you

2 ACCEPTED SOLUTIONS

Accepted Solutions
New Member

Re: Loss of first ping reply (C2950 - C3550)

If it is the first time you have pinged a device, or it has been an extedned period of time since your last ping, the lost echo-reply is a timeout due to an ARP request. The default ping timeout for IOS devices is 2 sec.

You could change the timeout setting for the pings. This is done during the ping:

2950#ping ip

Target IP address: 192.168.255.12

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]: 5

Extended commands [n]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.255.12, timeout is 5 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/202/1004 ms

2950#

This is a little clumsy. Most people just get used to the first ping timeout.

New Member

Re: Loss of first ping reply (C2950 - C3550)

I have seen this too, and only seems te be an issue witch occurs on the managment interfaces of certain equipment. regular traffic is NOT affected bij this.

I've allso noticed that these switches take somewhat loger to connect by telnet than routers so i guess it is the same issue witch in my opinion is purely cosmetic.

It seems to be related with learnig (arp) the mac adress of the switch.

Hope this helps

3 REPLIES
New Member

Re: Loss of first ping reply (C2950 - C3550)

If it is the first time you have pinged a device, or it has been an extedned period of time since your last ping, the lost echo-reply is a timeout due to an ARP request. The default ping timeout for IOS devices is 2 sec.

You could change the timeout setting for the pings. This is done during the ping:

2950#ping ip

Target IP address: 192.168.255.12

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]: 5

Extended commands [n]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.255.12, timeout is 5 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/202/1004 ms

2950#

This is a little clumsy. Most people just get used to the first ping timeout.

New Member

Re: Loss of first ping reply (C2950 - C3550)

I have seen this too, and only seems te be an issue witch occurs on the managment interfaces of certain equipment. regular traffic is NOT affected bij this.

I've allso noticed that these switches take somewhat loger to connect by telnet than routers so i guess it is the same issue witch in my opinion is purely cosmetic.

It seems to be related with learnig (arp) the mac adress of the switch.

Hope this helps

New Member

Re: Loss of first ping reply (C2950 - C3550)

Thank you,

I suspected some ARP or similar data timeout, but his was worrysome because it also could affect regular traffic (which we don't own).

It is a relief that it seems limited to switch management addresses. That is indeed the phenomenon which occurred.

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