CSS: Different Ping Sizes

mduhra · ‎08-25-2010

Hi, What I'm seeing is that some IP's are set for an MTU of 1472, while others are 34032 or 65500. How is this set and how can it be modified?

For Example:

circuit VLAN55

ip address 10.1.55.5 255.255.255.192 <----------- Can send ping of 34032 bytes

    ip virtual-router 55
    ip virtual-router 150 priority 105 preempt
    ip redundant-interface 55 10.1.55.4 <------------- Can only send ping of 1472 bytes

circuit VLAN255

ip address 10.1.55.66 255.255.255.192 <----------- Can send ping of 34032 bytes
ip virtual-router 255
ip redundant-interface 255 10.1.55.65 <------------- Can only send ping of 1472 bytes

circuit VLAN256

ip address 10.1.55.130 255.255.255.192 <----------- Can send ping of 34032 bytes
ip virtual-router 254
ip redundant-interface 254 10.1.55.129 <------------- Can only send ping of 1472 bytes

The VIP’s and real IP’s of the servers are exhibiting similar results.

Thank you in advance!

MD

yushimaz · ‎08-25-2010

Unfortunately, there is no option to enable ping more than 1472 bytes on redundant-interface.

CSS supports packets over 1500 bytes on the circuit ip address and mgmt ip address, but

there is a limitation on the redundant-interface ip address or any other ip address.

data(1472bytes) + icmp header(8bytes) + ip header(20bytes) = 1500 bytes

Since redundant-interface and vip address are virtual address, the behavior is different from

circuit ip address and mgmt address. You can check with 'shell 1 1 ifShow | grep Internet'

command whether the ip address is supported more than 1500 bytes or not

CSS11503(debug)# shell 1 1 ifShow | grep Internet

Internet address: 1.169.0.13 <<== Ethernet-Mgmt

Internet address: 127.0.0.1 <<== loopback

Internet address: 192.168.78.250 <<== circuit ip address

<<== ip address of redundant-interface is not present

<<== vip address is not present

CSS11503(debug)#

CSS11503(debug)# sh run circuit

!************************** CIRCUIT **************************

circuit VLAN777

ip address 192.168.77.250 255.255.255.0

ip virtual-router 1

ip redundant-interface 1 192.168.77.200

CSS11503(debug)# sh run owner

!*************************** OWNER ***************************

owner test

content test

vip address 192.168.77.100

add service sv1

add service sv2

active

CSS11503(debug)# sh boot-config

!************************ BOOT CONFIG ************************

ip address 1.169.0.13

subnet mask 255.0.0.0

primary boot-file sg0820402

primary boot-type boot-via-disk

CSS can handle and loadbalance fragments to vip address with 'tcp-ip-fragment-enabled' 
and udp-ip-fragment-enabled' command on global configuration mode, but it doesn't affect
icmp packets.

Regards,

Yuji