LANCOM routers provide the option of logging internal processes in order to diagnose errors. This trace function can be accessed from the telnet console or by means of the trace module in LANmonitor. Below you will find a IP router trace with the meaning of each message explained.
Application:
The purpose of the IP router trace is to check how the router processes TCP/IP packets which arrive at it.
You can check whether the packets were received and where they are forwarded to.
You can also recognize packets that have been filtered or rejected.
To do this, enter the command "trace + ip-router" at a telnet console.
Important:
Info
In LCOS 10.20 changes have been made regarding the IP-Router trace. These are described in the following article in our knowledgebase:
The destination address (DstIP) and the source address (SrcIP) are shown. Also shown is the packet length (Len), in this case 84 bytes, and also the DiffServ/Type of Service field (DSCP/TOS), in the case empty: 0x00
An answer packet from the Intranet is forwarded to the WAN remote station.
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Another data packet (this time the POP3 protocol):
[IP-Router] 2008/02/20 11:19:510.530
Timestamp, prefixed to every packet
IP-Router Rx (WLAN-1, INTRANET, RtgTag: 0):
The IP router has received a packet (Rx) from the physical interface WLAN-1 of the logical network INTRANET. This packet has the routing tag (RtgTag) "0"
The destination address (DstIP) and the source address (SrcIP) are shown. Also shown is the packet length (Len), in this case 46 bytes, and also the DiffServ/Type of Service field (DSCP/TOS), in the case empty: 0x00
Prot.: TCP (6), DstPort: 110, SrcPort: 4889, Flags: PA
Displayed here are the protocol (Prot), in this case TCP, the destination port (DstPort), in this case 110, the source port (SrcPort), in this case 4889, and the TCP flag of the packet
Route: WAN Tx (INTERNET)
The packet is transmitted to the WAN interface, the remote station INTERNET
The packets are filtered, because the address range is private and the routing table blocks these.
Meaning: The route to the destination network is blocked. For this reason the packet is filtered.
Possible causes:
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The route to the destination network is blocked. Check the destination address, create a dedicated route for the destination, or unblock the route if the destination network can be reached via the default route.