Hop up & down and sing with us!

[Igaduma]

Hi all,

When on a LAN, should the hop-count be always equal in both directions ?

this is my case:
My laptop on lan:

172.31.23.85
255.255.254.0
172.31.22.1

A server on a subnet in this Lan:

172.31.11.41
255.255.255.0
172.31.11.1

Traceroute from my laptop to server:
c:\>tracert -d 172.31.11.41

1 <1 ms <1 ms <1 ms 172.31.22.2
2 * <1 ms <1 ms 172.31.22.4
3 * <1 ms <1 ms 172.31.11.41

Trace complete.

Now traceroute from server to laptop:

# traceroute -d 172.31.23.85

1 172.31.11.3 (172.31.11.3) 0.629 ms
2 172.31.23.85 (172.31.23.85) 0.563 ms

(The 11.3 is Default Gateway 11.1 or 22.4)

So I have 3 hops from laptop to server & 2 hops from server to laptop.
Which leads me to believe that the 11.3 is directly connected on the same physical connection as my laptop, since it's knows it's mac adress & can reach it directly.

Our IT dep. doesn't think of this as a bad thing. COpying files works 9 out of 10.
Throughtput is very bursty.

If I however do this on my laptop:
add route 172.31.11.0 255.255.255.0 172.31.22.4
it works magically well.

I don't have any in-depth TCP/IP experience but I understand that the current setup is not really the way to do it.

What can I say to them in terms that they will understand what the problem is ?

Thanks.
Iga-Duma

 

[jpm121]

You sort of answered your own question in the middle there -- the laptop is on a different subnet and therefore needs to contact a router to pass to the new subnet's segment.

Adding a route statement takes care of this and results in just the two hops.

Good luck...

 

[Igaduma]

Hi Jpm121,

Yes, adding a router helps, but running it without that extra route added is that considered either a way to do it and accept that problem, avoiding other structural problems or more a way how not to do it ?

The trouble is that whenever clients on the subnet access servers far behind these 2 routers the problem exists where data is bursty & connection is very slow.
I'm suspecting the default router or gateway for these servers is also having the 3 hop route instead of the 2 hop route.

The only sane thing to do seems to activate a setting on the router for that seperate subnet which makes it only reply via the source router adress and not use some sort of broadcast on whatever is nearby.
Again, I have no experience in networking, i'm more guessing than anything here really.
2 hops up should mean 2 hops down or some sort of latency with dropped packets must exists.
The subnet is on full-duplex and the rest of the LAN is on half duplex, could this have anything to do with it?
IT dep assured us that routers take care of this mismatch between full or half duplex.

Thanks for any info.