IT Answers » Fault isolation

TCP Retransmissions b/c of Checksum Incorrect

Tbitner — Thu, 19 Jul 2007 15:55:13 +0000

We have a problem where some users will complain of slow application response time (on the LAN) from our ERP server, but others will be fine. After many hours of troublshooting I’ve discovered the following:

- Packet Sniff’s of affected users shows TCP Retransmissions because the Checksum is Incorrect from the server.
- Replacing the NIC card on the workstation temporarily fixes the errors. Then the problem may start happening on new NIC, so I swap back to old NIC and problem goes away for a while.
- Sometimes the problem clears itself up for certain people after a couple months.
- There is no similarity between NIC cards, drivers, versions, laptops, desktops, wireless.
- Affected users have been tested on different segments of the LAN with no success.

Dell Optiplex GX520 hibernation/sleep mode issues

Jmello — Tue, 26 Jun 2007 15:45:26 +0000

Question Edited by singhjeet

Routing Between Subnets and between networks

Chinmoymohanty — Wed, 10 Jan 2007 04:12:38 +0000

1.I have two separe networks 192.168.0.0 and 192.168.1.0 ,they r physicall connected. What should i configure and where to configure so that host of each network can connect to other host in other network.
2.I have two separe Subnets(after subnetting a class B network),they r physicall connected. What should i configure and where to configure so that host of each network can connect to other host in other network

odd NIC problem

TheVyrys — Fri, 20 Oct 2006 17:47:37 +0000

Howdy all…

I have a win2k3 member server with 2 onboard Intel PRO lan connections. One is 100mb the other 1000mb.

On the 100mb connection, I can set either a DHCP or Static TCP address and it works fine.

On the 1000mb connection, it works fine on DHCP, but absolutely refuses to connect with a static ip address.

I have checked many times the correct settings for DNS, and gateway, subnet mask, etc.
I flushed the DNS caches.
I deleted the ARP entries.

One error message I get in event viewer is:

Event ID: 4321
Source: NetBT

Message: The name “Server” could not be registered on the Interface with IP address 192.168.1.2
The machine with the IP address 192.168.1.1 did not allow the name to be claimed by this machine.

For reference the 192.168.1.1 is my PDC emulator.
The other machine is a member server.
any ideas?

Cisco Load sharing with port forwarding different ISP’s

Dimchik — Fri, 15 Sep 2006 13:42:42 +0000

I have a 1811 series router now its set with dual internet connections two different ISP’s I have 2 default routes basically It should load balance between two now my concern is I need a port forwarding as we use privite space addressing. I am including current config addresses have been changed to examples.
ip sla 1
icmp-echo 24.168.1.6
ip sla schedule 1 life forever start-time now
ip sla 2
icmp-echo 72.15.49.4
ip sla schedule 2 life forever start-time now
!
track 123 rtr 1 reachability
!
track 456 rtr 2 reachability
!
interface FastEthernet0
description $ES_WAN$$FW_OUTSIDE$
ip address 24.168.1.5 255.255.255.240
no ip redirects
no ip unreachables
no ip proxy-arp
ip nat outside
no ip virtual-reassembly
no ip route-cache cef
no ip route-cache
duplex auto
speed auto
!
interface FastEthernet1
ip address 72.15.49.3 255.255.255.0
no ip redirects
no ip unreachables
no ip proxy-arp
ip nat outside
ip virtual-reassembly
ip route-cache flow
duplex auto
speed auto
!
interface Vlan1
description $ETH-SW-LAUNCH$$INTF-INFO-FE 2$$ES_LAN$$FW_INSIDE$
ip address 192.168.1.195 255.255.255.0
no ip redirects
no ip unreachables
no ip proxy-arp
ip nat inside
ip virtual-reassembly
ip route-cache flow
ip tcp adjust-mss 1452
!
ip local policy route-map MY_LOCAL_POLICY-2
ip route 0.0.0.0 0.0.0.0 71.249.216.1 track 123
ip route 0.0.0.0 0.0.0.0 64.8.212.209 track 456
ip route 64.8.212.209 255.255.255.255 FastEthernet0 permanent
!
ip nat inside source route-map FAST-0 interface FastEthernet0 overload
ip nat inside source route-map FAST-1 interface FastEthernet1 overload
ip nat inside source static tcp 192.168.1.1 21 24.168.1.5 21 extendable
ip nat inside source static tcp 192.168.1.1 25 24.168.1.5 25 extendable
ip nat inside source static tcp 192.168.1.1 80 24.168.1.5 80 extendable
ip nat inside source static tcp 192.168.1.68 1528 24.168.1.5 1528 extendable
ip nat inside source static tcp 192.168.1.50 1529 24.168.1.5 1529 extendable
ip nat inside source static tcp 192.168.1.48 3388 24.168.1.5 3388 extendable
ip nat inside source static tcp 192.168.1.1 21 72.15.49.3 21 extendable
ip nat inside source static tcp 192.168.1.1 25 72.15.49.3 25 extendable
ip nat inside source static tcp 192.168.1.1 80 72.15.49.3 80 extendable
ip nat inside source static tcp 192.168.1.68 1528 72.15.49.3 1528 extendable
ip nat inside source static tcp 192.168.1.50 1529 72.15.49.3 1529 extendable
ip nat inside source static tcp 192.168.1.48 3388 72.15.49.3 3388 extendable
logging trap debugging
access-list 1 permit 192.168.1.0 0.0.0.255
access-list 1 remark INSIDE_IF=Vlan1
access-list 1 remark SDM_ACL Category=2
access-list 150 permit ip 192.168.1.0 0.0.0.255 any
access-list 189 permit icmp any host 72.15.49.4 echo
access-list 199 permit icmp any host 24.168.1.6 echo
!
route-map FAST-1 permit 10
match ip address 1
match interface FastEthernet1
!
route-map FAST-0 permit 10
match ip address 1
match interface FastEthernet0
!
route-map MY_LOCAL_POLICY-2 permit 10
match ip address 189
set interface FastEthernet1

What do you think guys will this config support load sharing with port forwarding?

Monitoring the Network

Maryam82 — Mon, 11 Sep 2006 00:51:02 +0000

Hi,
I have multiple remote sites. I would like to monitor the network and analyze the traffic and its performance in general. For example, how the bandwidth is consumed, if certain activities are unnecessary and how to improve the networks performance by blocking through the firewall like peer-to-peer applications, etc.
I am using check point as a firewall and Cisco as a router.
I came across an application called Websense that I can trial for free for a month. And I am searching how I can deploy my existing devices to help me with what I want, cause buying any addition is a challenge. Any suggestions are appreciated.
Thank You

Software based WIN Simulation

SADnBLUE — Wed, 30 Aug 2006 02:30:42 +0000

Hi,

I need to test out an application over WAN. The testing includes the response time with different delays and bandwidth requirements. Is there any piece of software (preferably opensource/freeware)which can simulate the WAN for me? The idea is to install two NICs in the Windows/Linux machine, put the software on and adjust delay and bandwidth to my requirements (just a hunch!) A workstation will be connected to one NIC and the Server will be connected to the second NIC. I heard someone saying that there is Java based software, not sure about that though!

Regards,

Muhamamd Ali

Network Resource Allocation cum Planning cum Technical Problem

Hunkgym — Mon, 15 May 2006 10:17:05 +0000

This is the real commercial problem face by my company. Well, the reason I ask this problem is I salute and respect all of you as I believe all of you are as good as network solution company out there, or even better!!

Lets me rephrase the entire problem again.

Company expand so fast that the IT infrastructure is not fast enough to cater high volume of traffic; the initial design is not scalable. The number of new branch offices setup caused the company pay a high price in the leased line communication.
Salesman and management staffs dial into company networks via 56K modem to access the database server and update the sale order. All the branch offices access the internet via HQ and download email via the external POP3 email server.
Plan to revamp their IT infrastructure and reduce the leased line access cost. Here are some of the feedbacks consolidated from the various country managers and local salesman.
1) The email downloading and sending is very slow. They receive a lot of spam email this caused their individual mailbox quota use up very fast.
2) The sales and marketing departments need to access the internet to search for latest news and market trends. But the internet speed is very slow. These people are irritated by spywares and popup often.
3) The File transfer and Database access is very slow even in the local area networks.

I decided to put the real network cum equipment diagram of my current company as I believe this will at least give INSIGHT in solving the problem.

Please visit the website http://www.hgym.photosite.com
for the diagrams which are network diagram and equipment diagram.

Now I plan to improve the IT infrastructure to cater for future expansion up to 10 countries. SAP will be implement to automate the overall company operation. Also expect 3rd party to access their server to submit and view sale order.

I also plan to redesign the network so that it is high available, scalable and secure.

Any suggestion and opinion? What is your comment after looking at my network and its insfrastructure (from the diagrams on http://www.hgym.photosite.com )
Any improving needed?

My email is hunkgym@yahoo.com Of course you can reply here, preferable :>

Thanks again for your opinion!! Thank You!!

Design NEW network cum NEW IT infrastructure-2

Hunkgym — Sun, 14 May 2006 08:21:45 +0000

http://www40.brinkster.com/hunkgym/NetworkEquipmentDiagram.bmp

Requirements:
~ Please design a new IT infrastructure to cater for future expansion up to 10 countries. SAP will be implement to automate the overall company operation. Also expect 3rd party to access their server to submit and view sale order.
~ Please design and high available, scalable and secure network.

My Email : hunkgym@yahoo.com

Thanks for your suggestion. Thanks AGAIN!!

static ip is in the spam list

UNIVERCITY — Wed, 12 Apr 2006 07:07:07 +0000

HELLO ALL,
My static ip is in the spam list. What should I do?

Thanks a lot