TTL curious

[Hacksawbob]

I have a webserver (esspreso box) which is on the same subnet as the clients that access it. If I ping any other host on the network I get a TTL=128 If I ping this box I get a TTL of 64. Does this mean it is going through a router to get there? I understood that the TTL would decrement each hop, however if I tracert this address it comes back with the one entry as it should for something on the same network. I believe that TTL can be set somewhere, is this set somewhere else, on the router or local machine? i have staff saying it's been flakey lately.

[powdarrmonkey]

I have a webserver (esspreso box) which is on the same subnet as the clients that access it. If I ping any other host on the network I get a TTL=128 If I ping this box I get a TTL of 64. Does this mean it is going through a router to get there?

 

No, it's just that the default TTL value for reply packets on that box is different to others that you've sampled. Valid values for TTL are 1 through 255.

 

I believe that TTL can be set somewhere, is this set somewhere else, on the router or local machine?

 

On a Windows box the echo request packet can be changed (see the documentation, http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/ping.mspx?mfr=true), but this does not affect the reply packet's TTL. To change that you need to change the default value on the remote box.

 

i have staff saying it's been flakey lately.

 

It's not going to be TTL troubles, unless you know that packets are going missing. Since you don't have a router boundary to deal with, your TTLs aren't being decremented anyway, so this is an unrelated problem.

[steve]

As powdarmonkey says, each different OS can use a different TTL:

 

OS/Device Version Protocol TTL value

AIX 3.2, 4.1 ICMP 255

BSDI BSD/OS 3.1 and 4.0 ICMP 255

Cisco ICMP 254

HP-UX ICMP 255

HP-UX TCP 64

Juniper ICMP 64

Linux 2.0.x kernel ICMP 64

Linux 2.2.14 kernel ICMP 255

Linux 2.4 kernel ICMP 255

Linux Red Hat 9 ICMP and TCP 64

NetBSD ICMP 255

Solaris 2.5.1, 2.6, 2.7, 2.8 ICMP/TCP 255/64

SunOS 5.7 ICMP and TCP 255

Windows for Workgroups TCP and UDP 32

Windows 95 TCP and UDP 32

Windows 98 ICMP/TCP 128

Windows NT 4.0 TCP and UDP 128

Windows Server 2003 128

Windows XP ICMP/TCP/UDP 128

[powdarrmonkey]

As powdarmonkey says, each different OS can use a different TTL:

 

Note, this table doesn't allow for local sysadmins making changes to the defaults.

[Hacksawbob]

Right OK red hering, looking for my issues elsewhere... apple wireless has had the long bony finger of suspicion pointed at it!