Ping size 1500

[dangkita]

Hi all,
I am using omni switch 6400. why i cann't ping size 1500 ?

[one6f]

According to CLI Guide this should work. Unfortunately, currently I have no 6400 to test it. I have tried this with 6850 and its works fine with 6.4.4.441
PS: When you specify the sweep-range in the ping command, you cannot configure the count and size parameters.

[dangkita]

hi one6f,
thank for helping me !
When I specify one ip address in the ping command, i can ping size 1470 but i cann't ping size 1472 and more ?

[one6f]

hi one6f,
thank for helping me !
When I specify one ip address in the ping command, i can ping size 1470 but i cann't ping size 1472 and more ?

Do you see any CRC errors/drops on the egress interface ?

The interfaces max frame command can be used to configure the maximum frame size.
Maximum values for this command range from 1518 bytes Fast Ethernet ports to 9216 bytes for Gigabit ports.
Consult the Network Configuration Guide for more details.

So much for the theory:
1472 bytes ICMP payload
+ 8 bytes ICMP header
+ 20 bytes IPv4 header
---
= 1500 bytes Ethernet packet
+ 14 bytes Header
+ 4 bytes Frame Check Sequence
---
= 1518 bytes Ethernet frame

The reason you don't see your icmp-data >1472, could be because you have exceeded MTU size of the egress interface. So, all of the data will not fit in the Ethernet packet. Hence the packet must be fragmented and the bit of fragmentation will be activated. Maybe you try to send a ping and add the option dont-fragment. Use sniffer to see communication details.

[dangkita]

Hi one6f,

Before ping with size 1472, i set the long frame size =9216.
But i couldnt ping.

Have you ever met the situation like that?

[one6f]

Hi one6f,

Before ping with size 1472, i set the long frame size =9216.
But i couldnt ping.

Have you ever met the situation like that?

no, simply trace with ethereal/wireshark on switch port and destination device