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Slow LAN network file copy performance when copied between subnets

I am having an issue as I try to migrate my basically flat network to a more robust subnetted network.  As a very basic design I have the following:

pc1(on new network)<-->access switch<-->distribution switch(layer 3)<-->firewall<-->router<-->layer 2 unmanaged switch<-->pc2(on old flat network)

Everything is Gigabit ethernet.  When I try to copy a file from pc1 to pc2, it is relatively fast at about 4MB/sec.  When I try to copy the same file back from pc2 to pc1, it is atrociously slow at about 100KB/sec.  I am able to test everything in a duplicate test environment and cannot duplicate the issue.  I suspect that it is the router because the router that is the only thing I don't have access to (because it is managed by our ISP) in the production environment and can verify in the production environment everything on either side of it works just fine.

I have also tried hard-coding speed and duplex at each location to no avail.  Setting 100 M half actually didn't work on the "new" end of things so I didn't continue to the old.

Any help is greatly appreciated.  Thanks in advance!
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2 Solutions
Darrell PorterEnterprise Business Process ArchitectCommented:
If your diagram is correct, and the traffic from PC1 to PC2 is traversing both the firewall and the router, which is likely the issue due to traffic-shaping on the router, for what reason do you not connect the old layer 2 unmanaged switch to a port on the new distribution switch as a separate VLAN/subnet?
uescjpAuthor Commented:
That is a great idea. I am not too familiar with traffic shaping but I am guessing that it is the same as QOS. Please correct me if I'm wrong.

The reason I am not connecting the old subnet to the distribution switch is I was trying to avoid any situation that I make part of the change and something doesn't work. If I keep them separated like this, it is very easy to go back even partially to the old network.
SurranoSystem EngineerCommented:
If my reading is right, it is not really a LAN config, you have one element: the ISP router, that is connected to the Internet (i.e. leads outside your house). I'm trying hard to imagine a situation how traffic may go from one direction to the other within LANs, and the other direction through the uplink of the router but I believe we can rule it out by means of traceroute in both directions.

Are the list of hops the same (just inverse order)?
Are the response times comparable to each other?
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SurranoSystem EngineerCommented:
Plus: what if you introduce another device (simplest: a notebook) first to new net, then to old net, testing transfer to/from both pcs? (you may get some surprise, e.g. pc2->nb being too slow even if pc2 and nb are in same network)
uescjpAuthor Commented:
@Surrano Yes, file transfer is the problem not ping connectivity.  Traceroutes complete in both directions and in the inverse order.  All are equal to or under 1 millisecond.

New devices on either side act the same way as the original devices.
uescjpAuthor Commented:
@WalkaboutTigger  The following is what I can guess is the traffic shaping config on my ISP managed router:

class-map match-any ef
 match  dscp cs5  ef
class-map match-any be
 match any
class-map match-any af4x
 match  dscp cs4  af41  af42  af43
class-map match-any af3x
 match  dscp cs3  af31  af32  af33  cs6
class-map match-any af2x
 match  dscp cs2  af21  af22  af23
class-map match-any af1x
 match  dscp cs1  af11  af12  af13

Open in new window

And this is the policy-map:

policy-map etm
 class ef
  set ip dscp ef
    priority 3012
 class af4x
    bandwidth remaining percent 40
  set ip dscp af41
 class af3x
    bandwidth remaining percent 39
  set ip dscp af31
 class af2x
    bandwidth remaining percent 16
  set ip dscp af21
 class af1x
    bandwidth remaining percent 1
  set ip dscp af11
 class be
  set ip dscp default
    bandwidth remaining percent 3

Open in new window

I only see on the multilink interface any mention of "service-policy output etm" which I would think (quite possibly incorrectly) is only going to shape the traffic going across that multilink interface (across our MPLS).  The GigE lan ports do not mention any service-policy on the interfaces.  Does that help any in ruling out traffic shaping as a potential issue or does it point more toward it as being the problem?

I am currently reading up on traffic shaping to see if I can decipher one way or another as well.

Thanks again to you both for the assistance so far.
uescjpAuthor Commented:
Would a multilink interface being down possibly negate any service policy that would otherwise being effecting other interfaces?  This is again copied from the config of the router supplied to me from my ISP.

interface Multilink1
 description Possible cause of slowness
 ip address
 no peer neighbor-route
 ppp chap hostname blah
 ppp multilink
 ppp multilink links minimum 1
 ppp multilink group 1
 ppp multilink fragment disable
 service-policy output etm

Open in new window

uescjpAuthor Commented:
It also is making sense to me that this is happening but I don't know why.  Mainly because the "show policy-map etm" on my test router is showing a default bandwidth of 3012kbps which would compare to the 3-4Mb/sec I see in the file transfer in the one direction that it isn't really bad.
uescjpAuthor Commented:
The issue I was seeing was actually due to a wan optimization device between the router and layer 2 unmanaged switch that was throttling the network speed down to 8mbps. That was removed and speeds picked up to what was expected.
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