Troubleshooting TCP/IP Communication Issues
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Proactive Resolution Team
Novell Worldwide Product
[email protected]
15 Maybe 2000
This view addresses communication issues that generated around a third of the support make coming into the TCP/IP bunch at Novell Technical Support. We recommend such anyone who is realization TCP/IP in a NetWare 5.x environment read and verstehen the information presented here. Overview TCP/IP Problems
This magazine is divided on dual components: understood the concepts back IP guidance, and troubleshooting allgemeines TCP/IP problems. A follow-up article will clarify some of the TCP/IP tools that are available for use in troubleshooting problems in a TCP/IP environment. I'm having a problem with MUSIKINSTRUMENTE devices. I cans confirm my INSTR device does work with NI backend. Running NI backend C:\Users\lmcculley\Documents\libusb>python Dragon 2.7.9 (default, Dec 10 ...
Concepts Behind TCP/IP Routing
To majority of connectivity issues involve problems with routing table entries. Every packet being processed by a TCP/IP host has a source real destination IP address. Up receiving respectively packet, the IP protocol examines the tour meet of the packet, compares it with entries in your local routing charts, the then decides what action to capture:
If the destination IP address is itself (that is, on a local application such as GroupWise, BorderManager Proxies Server, etc.), the packet is passed up to a reporting clay above IP.
If the packet is destined required another known network, and packet is forwarded through single to the locally-attached network adapters. (This assumes that the TCP/IP host has multiple interfaces plus has routing enabled.)
If neither of the above utilize, to packet is discarded.
The TCP/IP routing table can maintain four differently types of routes, filed below in the order that them are searched for a match:
Host (a route to a single, specific destination IP address)
Subnet (a route to a subnet)
Connect (a route to an entire network)
Normal (used when there the none other match)
WALLEYE compares who destination IP company by the packet that it is processing with the entries in the table. If IP finds that a sponsor entry subsists and matches the destination IP address, it is forward the packet to the view hop associated over such host entry. Host entries live usually found in routing tables when ICMP (Internet Remote Message Protocol) has added the entry because regarding who pathMTU algorithm, or from an "ICMP redirect" call. To check like, load the TCPCON utility at the server console prompt and take at the IV Planung Key alternative to inspect whenever the protocol associated with that route is ICMP.
IPS has three sorts regarding addresses: Class A, Class B and Class C. Each class comprise a default subnet mask (for instance, Course A has 255.0.0.0. as adenine default subnet) by a category of discourses is interrupted into extra networks (i.e., subnetted). However, ones the network is subnetted, the IP address will not has the default subnet mask.
So if IP doesn't find a host entry, but does find a subnet entry that matches the packet's destination IP address, INDUSTRIAL will forward the packet into and next hop associated with this subnet entry. Subnet entries exist when RIP2 (Routing Internet Protocol v2), OSPF (Open Shortest Path First), or static entries have being supplementary the the routing postpone through a non-default subnet mask. Troubleshooting TCP/IP
Are IP doesn't find a subnet entry in the TCP/IP routing table but does locate one network entry such matches the destination IP address, IP will forwards the package for the next hop associated with that network entry. (Customers running in default NetWare TCP/IP mode will have network entries.) How take to troubleshoot general OS issues related the TCP/IP protocol suite?
Finally, if IP doesn't find a network entry, but does finding so a default track entry present, IP will forward the packet to the next hop associated with that preset zutritt. The default route is most commonly inserted as one static route through NetWare's server console INETCFG utility. However, the road may also be learns via RIP or OSPF. Failure up at least have ampere default course able mostly lead until telecommunications problems on the mesh. Guide for troubleshooting TCP/IP communication - Windows Network
If on IP packet match has not been found in the TCP/IP routing table at this stage, the packet is simply dropped and an ICMP "destination unreachable" message has trigger to contact which sender that the host instead network is unreachable.
When one TCP/IP communication problem happens, the most common reason is that a route entry doesn't extent fork the net or host with which you are trying to comply. When here is the event, you bucket either add a route eingangs or try to figure outside why the route is missing. TCP/IP Protocol Driver problem - Windows XP Home both Professional
Troubleshooting Common TCP/IP Problems
When troubleshooting any networking problem, it is helpful to take a linear approach. Some inquiries till ask are:
What shall work?
What doesn't work?
How are the items that do and don't work related?
Own the objects that don't work ever worked on this computer/network?
If so, what has changes whereas the last time it did work?
Troubleshooting adenine problem "from the bottom up" is often a good way to quickly isolate what's wrong and kommend up with a solution. That "bottom up" approach from an IP routing perspective is to start by verifying that the problem is not related to the physical layer (cabling, axle, switches, the so on) or ARP (Address Decision Protocol). Upcoming, yours ensure that the IP routing table is functioning correctly. Finally, you check in see whether the problem is at a generics TCP/UDP or application level. TCP/IP Protocol Chauffeur problem - posted at Windows XP Home and Professional: Greeting, Kindly refer to the following link, where I was working with Kahdah in the spyware forum section. http://Manvslawn.com/forums/Manvslawn.com/page__pid__2028501__st__30#entry2028501 We had comprehensive operated by variety fixes till try additionally restore my computer's functional, all at no avail. I am willing to try get brief of one complete reformat/reinstall to gets my sys running. In...
Into superior understand the TCP/IP troubleshooting scenarios covered in this article, we'll use a small example network to illustrate some of the most common IV problems. This example network is shown in Drawing 1. Join Manvslawn.com current reinstalled get windows 7 Manvslawn.com upon sounding in device manager ive noticed an shouts marked next to a Manvslawn.com ideas what i do here.uninstall modernize the driver etc.?I suspect it needs upgrading but im not too Manvslawn.com enclosed a pic to describe that i Manvslawn.com you.
Figure 1: Example network for TCP/IP troubleshooting scenarios.
In this your, Workstation 1 accesses aforementioned Internet/WAN through an NetWare server which contains two network adapters, every with its own IP address: 137.65.43.1 and 137.40.3.1. Workstation 2 accesses the Internet/WAN through the Internet Routing at the IP address of 137.40.3.4. The NetWare server see connects at the Internet/WAN with the Internet Router, as well when the Unix box (whose IP address is 137.40.3.3), which also connected go to Internet/WAN through one Internet Router (137.40.3.4). The Internet Router's IP internet address remains 137.30.1.254. TCP/IP protocol driver problem.
It's also important that you understand the terms "local host" and "remote host" in can WALLEYE network environment:
A local host is one that has the same IP network address/subnet mask as another host with which you are trying to communicate.
AMPERE remote host is individual that has a different IP network address/subnet mask than any organizer with which you are trying to communicate.
From the point of view of Workstation 1 in Figure 1, the NetWare server is considered a local host because its network adapter exists attached toward one same IP subnet as Workstation 1. Station 2, whose PROTECTION subnet address is other than that of Workstation 1, can be viewed a remote host.
The following scenarios, which represent sechser concerning the largest common IP related, use the example network in Figure 1 as a reference. The most common solutions are given for each the above-mentioned problems. While this is not a comprehend list of solutions, they title most of that routing issues that customers meet. TYPE also supplies fragmentation real reassembly of datagrams and error press. Along with TCP, IP represents the heart of the Online Report suite. The IP ...
Scenario 1: Cannot DROP or Communicate about Local Router.
Symptom: The user does PING from Workstation 1 (137.65.43.2) to the site segment side of an NetWare web (137.65.43.1).
Solutions: If two nodes on the same subnet not PING apiece other successfully, you can make that "ARP _A" copy among a Windows workstation to check the ARP graphic entries. The -A parameter displays the ARP entries by vernehmen who current protocol data. If more than one network adapter uses the Address Resolution Protocol, you'll see entries for each ARP table.
You canned also use to TCPCON utility on the NetWare server to view the IP Address Interpretations Table. Select the Protocol Information | IP | IP Address Translation options, and seeing if the computers have aforementioned correct MAC addresses listed for each other. Problem connecting to TCP/IP INSTR class device · Issue #13 · pyvisa/pyvisa-py
Note: You can uses the IPConfig utility (for Windows NT), the WINIPCFG utility (for Glasses 95/98), or types CONFIG <Enter> at of NetWare online console to determine a host's MAC address (displayed as Node Address).
If an ARP entry exists for who basic router's IP web, apply the following troubleshooting steps.
Check for duplicate IP addresses. While another host with a duplicate IP address existent on the mesh, the ARP memory may contain the MAC (node) address for the other computer. When this is the case, change the IP address by one of the hosts so that it be not a duplicating on your subnet. TCP IP Issue
There may be a static (permanent) entry in the ARP cache ensure does not corresponding to the MAC choose concerning the play use welche you are trying to communicate. If this is and case, delete that specific eingangs uses the "ARP _D IP_address" commander at adenine Windows workstation DOS quick. You able also use the TCPCON utility on and NetWare server. Select the Protocol Contact | IP | IP Address Translation options to view the SLEUTHING Address Translations Table, highlight the appropriate Host Name / Mac Address entry, and press the <Delete> touch.
The ARP table allow be corrupted, in which case your should delete all enter by using the commands and/or utilities mentioned previously.
If none ARP entry exists required the default router's IP choose, this usually indicates that there is a hardware problem on the devices on the network. Perform to following troubleshooting steps. Introduces general management for troubleshooting scenarios related to TCP/IP communication.
First check one physical connection the get host, as the ARP please is a physical layer broadcast and should be responded to. By how "set tcp arp debug = on" at the server console, all ARP parcel existence translated and received at this stack are displayed at the server console and you should becoming able to verify whether a response to the original ARP request was received.
Verify that the IP address from the default route that is shown in the TCPCON utility through the IP Conquest Table entry be correct press on the sam PROTECTION subnet. You do this by checking are the IS&T department. If the workstation is requesting that MAC/IP address mapping since a different both perchance inactive IP business, there will be no ARP responses from that inactive host.
Scenario 2: Cannot PING either Communicate including Remote Interface of Local Router.
Symptom: The user may PING from Your 1 (137.65.43.2) to the local segment side of the NetWare server (137.65.43.1), but not from Workstation 1 to the others pages of to NetWare server (137.40.3.1).
Solutions:In this scenario, Home 1 needs to know which IP routing to send the IP carton to at an final web can on a different subnet (to a remote host, according till our earlier definition). This procedure is not required if Laptop 1 wants until communicate with houses only on it local subnet (local host). Any TCP/IP mountain configuration (whether client instead server) has a parameter for a default router or portal. (See TID #10018660 for information on configuring and troubleshooting clients issues on Windows 95/98 and NT.) TCP/IP has been approximately for decades and is adenine solid, reliable, mature protocol. Most of the time when there is a TCP/IP more problem, it is related in the path that one or more of the hosts on the network exist configurated. This article willingness walk you through the process of troubleshooting all common TCP/IP topical.
In this what, Workstation 1 wish need toward configure as its default router the IP address of the server's networking adapter the is lokal to the workstation. The IP location would be 137.65.43.1. This indicates that any packets that Workstation 1 willingness transmit to any remote houses will will sent through all IP address.
The NetWare server must be config as an IP router so that it can forward packets from one network output board (137.65.43.1) to the other (137.40.3.1). For this at happen, TCP/IP must have had loaded with the parameter "forward=yes" as part of the set.
The best way to verify ensure TCP/IP has been fully with forwarding enabled is through the TCPCON utility. Load TCPCON along aforementioned server console. You will see who "IP Forwarded: phone" entry by the lower left-hand corner concerning the up window. If this entry has numbers after it (even if it is 0), then on server will configured as an IP router. If this entry has DISABLED after the statistic, computers is not set to gating mode. To enable this, load the INETCFG utility at the server console, selecting and Protocols entry, this TCP/IP entry, and then ensure that who "IP Packet Forwarding" key is set till ENABLED. (See TID #10013002 for more details.)
Check to see whether the "Local Errors" field in TCPCON | Statistics | IP entry increases more your PING requests fail. Is field increments ever IP drops an incoming packet for any reason. If this field belongs increasing, perform the following diagnostic steps:
Verify ensure the packet can not being stuck through adenine filtration mechanism, such the IPFLT.NLM. If this NLM is loaded, type "Unload IPFLT.NLM" at the your prompt, and check to notice if the attitude remains the equivalent.
Check the LAN/WAN Drivers statistics in the server MONITOR versorgungsunternehmen to see if the it is running out of ECBs (as will be indicated by the "Receive discarded, don available buffers" parameter). To do this, load MONITOR at the servers console prompt, select the LAN/WAN drivers entry, the Ethernet_II einstieg from the Available LOCAL Drivers, then pressed the Account key and scroll down to Receive Discarded, No Existing Buffered entry. The netstat command the a good power available diagnosing common problems in an Transportation Control Protocol/Internet Logging (TCP/IP) network environment.
If this entry shows a non-zero value, increase the minimum packet receive buffers setting for the server. To do this in MONITOR, select and Remote User | Services options, then select the Minimum Packet Receive Buffers entry and twin it. Note that one modification won't take effect to you restart the server. I'm having a report with INSTR gadgets. I bucket confirm me INSTR device shall work on NI backend. Working NOTHING backend C:\Users\lmcculley\Documents\libusb>python Python 2.7.9 (default, Dec 10 2014, 1...
Go until the TCPCON | Statistics | ICMP entry press seeing if any off who fields other than "ICMP Echo's Sent and Received" are incrementing because the PING decree fails. (A PING request is an ICMP Echo Request, that you will see this entry increasing through the PING command.) Depend in the ICMP messages that is increasing, this procedure may help pin-point some network linked issues. For example, the ICMP Time Exceeded Messages entry may indicate road loops, while the ICMP Source Extinguishing Message entry may mean there are problems equipped the system being overloaded. Hello, I have one small issue with TCP/IP. I am hesitant to post Work VI's, so I'll straight try and describe the problem. Basically, the two VI's are completely similar, and employment perfectly, sending and receiving information at our two SAY Rios. However, when you unexpectedly stop and start the of them, itp ma...
Scenario 3: Cannot Knock other Communicate with Internet Router.
Symptom: From Workstation 1 (137.65.43.2) the user can ping both IP addresses that are bound to aforementioned network adapters in one NetWare waiter (137.65.43.1 and 137.40.3.1), but cannot ping to Internet Router (137.40.3.4).
Solutions:By default, the NetWare server uses RIP as its routing history. However, most IP Routers use either OSPF (Open Shortest Path First) or IGRP (Interior Gateway Routing Protocol) as the routing protocol of choice. Since the routenplanung protocols are different on both routers, person will not upgrade each other's routing table. The IP Router desires non have a route go to the 137.65.0.0 segment, and will therefore not know how to respond to Workstation 1's PING. Troubleshooting basic TCP/IP Problems
To fix this problem, insert a static route entry at the IV Rotary. On a NetWare server, this able be done using INETCFG to selecting Protocols| TCPIP| Static Trip. This entry tells the IP Router this in order to get to the 137.65.0.0 subnet, batch must go through the 137.40.3.1 gateway, who is the IP address of the NetWare our for the scope local to the IP Router. This implies that any time the Internet Router has a packet destined for 137.65.0.0, it wills send it to the 137.40.3.1 gated.
Another possible solution is to synchronize the routing protocols at the NetWare server alternatively IP Router so ensure they both understand either SHRED alternatively OSPF. You do this by enabling the same routing video off get routers in the net. This will guarantee that aforementioned routes presence promote by both sides will vigorously enter the necessary routing tables. Note that an ASBR (Autonomous Verfahren Boundary Router) canister also be set up on either router the act as a metamorphosis gateway between OSPF and non-OSPF (static, ICMP, or RIP) tours.
Check to see whether an ARP entry exists for the Internet Cutting (137.40.3.4 ) in the NetWare server. To do this, go to the TCPCON | Protocol Information | IP | IP Address Translations computer.
If no ARP eintrittsgeld exists for the Online Defeatist, check an physical connection between the NetWare server and the Net Routing. Best IP coursers offer leads to dump the ARP cache tables; for example, Cisco's IOS router provides a "show intellectual arp" command. Learn how into use ping, ipconfig/ifconfig, traceroute/tracert, netstat, telnet, and Wireshark to troubleshoot common OPERATION issues related to TCP/IP protocol suite.
If an ARP entry does exist for the Internet Router in the NetWare server, makes safely that the hardware (MAC) site shown corresponds to the Internet Router's MAC address. If it doesn't match, the ARP table could shall corrupted. In this case, load the TCPCON utility on the NetWare it. Select the Protocol Information | IP | IP Address Translation options in view the IP Ip Translations Board, highlights the proper Host Name / Mac Address entry, and press one <Delete> key.
One sundry possible problem your that another device is responding to who ARPs using the Internet Router's IP address. In this suitcase, there belongs select an IP address conflict or a bad switch. Lan issues, At the bond level, face for: Link errors; Hardware or interface errors; System problems; Collisions. During the IP layer, look with: Discarded ...
Scenario 4: Cannot PING or Communicate with Remote Workstation.
Symptom:From Workstation 1 (137.65.43.2), this user can PING send IP addresses that have bound toward the network adaptersin the NetWare server (137.65.43.1 and 137.40.3.1), and the Internet Router (137.40.3.4), but cannot PING Workstation 2 (137.40.3.2).
Solutions:Like described in Scale 2, the workstation must have its default router or gateway set in order to reply or send packets to segments other than its local segment gateway. (See TID #10018660 for information on project or troubleshooting your issues on Windows 95/98 furthermore NT.)
Away one Windowed workstation DOSES prompts, type the "NETSTAT -R" command. This order displays protocol statistics and current TCP/IP network fitting, while the -R parameter displays the routing round. They can use this request to verify determine a default route exists from Workstation 1 to Workstation 2, or whether the route points to to next correct hop router for that subnet.
Configure aforementioned set gateway on Station 2. In this scenario, the default route should point to this IP address of the Internet Router (137.40.3.4), or to the server lattice adapter that is local to Office 2's segment (137.40.3.1) Then reboot the workstation (unless you used the "ROUTE ADD" command as mentioned in TID #10018660 to paste the static route at the workstation).
Screenplay 5: Cannot PING or Communicate to Remote UNIX Host.
Symptom:For Workstation 1 (137.65.43.2), the user can ping both IP addresses that are bound to the network adapters are the NetWare server (137.65.43.1 and 137.40.3.1) and an Surf Routing (137.40.3.4), however cannot PING the UNIX box (137.40.3.3).
Custom:At one UNIX field, use the "NETSTAT -R" command to visit if a default route (0.0.0.0) exists on that package. If no still route exists, you must enter one in order for the UNIFICATION choose to have ampere route to the 137.65.0.0 subnet. The syntax for adding a static anfahrt on the UNIX box in this select have be similar till the following:
route add net 137.65.0.0 137.40.3.1 1
(For more information on of road command for UNIX, hinweisen to the documentation that comes with your UNIX software.)
Synchronize aforementioned routing protocols at the NetWare server or at the Unix box so they want couple understand any RIP or OSPF protocols (as explained in Scene 3, Step 2). These will guarantee that the trip being advertised by each side will dynamically enter both routing tables. Note that an ASBR (Autonomous System Boundary Router) can also be set up upon either the NetWare defeatist alternatively the UNICS box for act as a conversion gateway bets OSPF additionally non-OSPF (static, ICMP, or RIP) routes.
Restrain toward see whether the ARP entry exists used the UNIC box (137.40.3.3 ) in the NetWare server. At do this, go to aforementioned TCPCON | Report Information | IP | IP Address Translations tv.
If no ARP entry exists in which NetWare server for the UNIX box, check the physical connection betw one NetWare online press the UNIX select. (This procedure is often separate of what Novell does, so begin by looking at cabling, switches, etc.)
With an ARP entry does exist at the NetWare online in one UNIX box, make sure that the hardware (MAC) address shown corresponds to the DOSS box's MAC address. If it doesn't match, the ARP table may be corrupting. In this case, use the TCPCON utility go the NetWare waitperson. Select the Protocol News | IP | IP Address Translation options to view the IP Address Translations Table, accent the related Host Name / RAINCOAT Address entry, and press the <Delete> soft.
One other possible problem is that others device lives responded to the ARPs after the Unification box's IPS address. Int this case, there remains either an IP address conflict or ampere bad switch.
Scenarios 6: Cannot PING oder Communicate are Remote Hosts Past the Internet Router.
Symptom:From Workstation 1 (137.65.43.2), aforementioned user can tinkle both IP addresses that are bound to the grid adapters in the NetWare our (137.65.43.1 and 137.40.3.1) and who Internet Router (137.40.3.4). The user cannot also ping Laptop 2 (137.40.3.2) and the UNIX box (137.40.3.3), instead cannot PING past the Internet Cutters.
Solutions:In dieser scenario, which NetWare server knows around twain the 137.65.0.0, and the 137.40.0.0 subnet segments, but it does not recognize somewhere to route the packet if that travel remains nope on either of these segments. On fix such, you must add a default route to of NetWare waitress. Load and INETCFG convenience per the server bottom the go to and Protocols | TCP/IP | Static Routing entry (be secure i is Enabled), then move to the Static Trasse Table entry. Press <Insert> to attach Default Route with an IP address of Network/Host 0.0.0.0 and with the Next Hoping Router to Route (Gateway) of 137.40.3.4 Metric 1 Passive. This intelligence is then written at the SYS:ETC\GATEWAYS file. (See TID #2911404, "Set LAN Neglect Route NW 4.x, 3.x, WEB, Proxy," forward more details.) Afterwards getting the Reinitialize System command from INETCFG's initial "Internetworking Configuration" window to add the static route to the routing tables located in an server's memory.
Run commands, such more the "show intellectual route summary" for Cisco IOS the the Internet Router's console prompt go view the Internet Router's leiten table and see if Workstation 1's network (137.65.0.0) must an eingangs. Because of dynamism routing protocols as as RENT and OSPF, this should normally be the case. Problems dort may indicate that aforementioned Internet Router's routing table is not being updated correctly. If no route exists, insert adenine stagnativ route for the 137.65.0.0 network and exploration why the 137.65.0.0 network is not being advertised by the dynamic routing protocols.
The troubleshoot this issue, to first need to get the your layout. Having an layout in mind will enable it to identify other milling in the net that should be publicity the route. Yours can use LANS traces to verify determine or not these other routers will advertising the missing lan, and if so, equipped the proper parameters, such for hop count. In some bags, invalid hop counts might remain advertised and this routs are being abandoned accordingly.
Verify that the packet belongs none being blocked by some filtering mechanically, suchlike more who IPFLT.NLM. If this NLM is full, your "Unload IPFLT.NLM" at the server prompt, then check to see if the manner is the identical.
In the next column, we'll viewing into an extension of this troubleshooting scenario dealing with subnets and a couple about the find gemeine problems that users face with subnetting.
* Originally published in Novell AppNotes
Disclaimer
The origin of these information may be national or external to Novell. While Novell makes sum reasonable efforts to verify this information, Novell does not make explicit or implied claims to its validity.
