05-09-2010 09:58 PM
ping routing-instance size 1472 172.31.16.2 ---> success
ping routing-instance size 1473 172.31.16.2 - --> fail
ping routing-instance size 1474 172.31.16.2 - --> fail
ping routing-instance size 1475 172.31.16.2 - --> fail
ping routing-instance size 1476 172.31.16.2 - --> fail
ping routing-instance size 1477 172.31.16.2 - --> success
When the fragment started because of MTU 1518 on Juniper MTU 1500 on cisco .
Ping fails. It seems that fragmented packet is not reconstructed again. Between 1473- 1476 bytes
Is this bug ?
05-10-2010 10:55 PM
Are there any recommendation MTU between Cisco 6509 and Juniper Ex 3200
suppose 1518 is not enough. as Vlan tag is 4bytes at leaset we need 1522 on Ex3200
and over 9221 on cisco side. as there are no option for 1504 bytes.
if we change the MTU. suppose reslove the ping issue.
what everybody think?
05-13-2010 10:26 AM
Juniper MTU 1514 bytes is equivalent to Cisco's MTU 1500. Juniper adds the overhead, Cisco doesn't in the number. So specifying MTU of 1514 on Juniper is 1500+14 overhead. Cisco just uses the 1500 and adds the overhead for ethernet.
05-17-2010 07:04 PM
Thank you for the info.
during 1473- 1476 bytes, Packet fragments becasue of MTU. but look like never assembled. as ping fail
after using above 1477 bytes, it starts to be successful is this know bug?