MTU setting - solaris 9 how to check??

UNIX Solaris
1

I need to check the mtu setting on my server, I am told I need to use the ndd command and check the tcp setting tcp_mss_max

I have done so and all I can see is the below,

tcp_mss_def_ipv4 (read and write)
tcp_mss_max_ipv4 (read and write)

How can I check the actual value of the mtu setting, as far as I know the max value can be 1500 but I do not know how to check the actual value on my server, all I can see is the read and write above...

Anyone know how I can check this?

2

hmnnn I think i found my answer;

>> netstat -I hme0

Name Mtu Net/Dest Address Ipkts Ierrs Opkts Oerrs
hme0 1500 xxx xxxxx xxxx xxx xxxx xxxx

Collis Queue
xxxx xxxxxx

3

Also, as root, ifconfig -a

4

Frustrated1,

the command you are typing for tcp_mss_def_ipv4 and tcp_mss_max_ipv4 appears to be this:

ndd /dev/tcp \?

this will only show you the available parameters for /dev/tcp and whether or not they are read only or read/write. The commands you may want to use are:

ndd /dev/tcp tcp_mss_def_ipv4
ndd /dev/tcp tcp_mss_max_ipv4

You do not need to use the -get after ndd. If the kernel does not see -set, it assumes you want to get the settings value, not change it.

5

Also, if you are using Ethernet, the typical MTU will be 1500. An instance where you would see a different MTU value would be for the loopback interface (lo0), and modem connections. IIRC, those are typically 296. One final note...if you use ndd to change a setting in one of the modules in the TCP/IP stack and suddenly find you cannot communicate at all, reboot the host. This will return the settings to their original configuration. ndd is only in effect as long as the box is up and running.