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Slowness-routing/network problem??

Preston Gallwas
Valued Contributor

Slowness-routing/network problem??

See attached file.

Basically, at one of our highschools we've got some slowness doing basic stuff on the network - such as groupwise e-mail, loading files, etc.

I captured 700mb worth of data today to try to sift through it, and I was surprised to see the following that is illustrated.

The server is talknig to a client
The server ip is set as the src, client ip is dst
The server mac is the src mac, the router is set as the dst mac.

Now, my reasoning in my head is that it is because the server doesn't know a route to the 202 subnet - but, as you can see, we shape the outbound traffico n that packeteer down to 3mbit...could this be what is causing the slowness? Or is the routing/network scenario not set up properly? Should the server know to send directly to the routing switch?

Arg. Any help understanding what I'm seeing here would be great.
4 REPLIES
Matt Hobbs
Honored Contributor

Re: Slowness-routing/network problem??

I think you've found your problem there, it makes sense to me.

What I would do is change my default gateway on subnet 1 to point towards the 6108 (6308?) instead, and on the 6108 have it's default route set to 152.157.52.1.
Manfred Arndt
Valued Contributor

Re: Slowness-routing/network problem??

Hi Preston,

Yes, shaping down to 3mbit on an Ethernet lan can dramatically slow down performance and is not something I would recommend -- unless of course, you are intentionally trying to limit bandwidth.

This is appropriate and often recommended on a high-latency WAN link. But the smaller TCP window size combined with additional latency can dramatically slow down performance on a high-speed local LAN.

As Matt indicated, changing our routing should improve things.

Cheers
Preston Gallwas
Valued Contributor

Re: Slowness-routing/network problem??

Well,

as far as I can tell with the shaper, the local LAN traffic should be assigned to the SAMESIDE class which is ignored and note shaped -

So far, we've added static routes in the servers themselves to the LAN subnets, and my latest captures indicate that the router isnt being used. I'm still trying to find a way to use the packet capture data to quantify and verify if there was an improvement (aside from the surprising lack of retransmissions during the first second of the conversation...)

Diego Castelli
Trusted Contributor

Re: Slowness-routing/network problem??

Hi, old thread, i know...

if the client is the destination IP and the MAC address is the MAC of the router...

this could be a MITM attack with ARP poisoning from the client to the server, putting its PC in promiscous mode to have the MAC of the router assigned to him.

so all traffic from the server (and perhaps from other clients too) is passing through the client and, perhaps, saved (for a further analysis).

wasn't so?
Diego C.

MS MCSA Server 2003

HP Accredited Integration Specialist