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Troubleshoot Traceroute

 

About Traceroute Page

You are here: Administration > Tools > Traceroute.

The traceroute diagnostic tool uses a series of packets crafted to elicit an ICMP "time exceeded" messages from intermediate points in the network between your device and the specified host.

The time-to-live for a packet is decremented each time the packet is routed, so traceroute generally receives at least one "time exceeded" response from each way point. Traceroute starts with a packet with a time-to-live value of one, and increments the time to live for subsequent packets, thereby constructing a rudimentary map of the path between hosts.

Use this page to display a list of routers between the device and a specified destination host.

To use the traceroute tool:

  1. Click the expand icon next to Advanced options.
  2. Enter information in the Traceroute page as described in Table 1.

    The Remote Host field is the only required field.

  3. Click Start.

    The results of the traceroute operation are displayed in Table 2. If no options are specified, each line of the traceroute display is in the following format:

    hop-number host (ip-address) [as-number]time1 time2 time3

    The device sends a total of three traceroute packets to each router along the path and displays the round-trip time for each traceroute operation. If the device times out before receiving a Time Exceeded message, an asterisk (*) is displayed for that round-trip time.

  4. Click OK to stop the traceroute operation before it is complete.

Table 1: Ping Traceroute Troubleshooting Options

Field

Action

Remote Host

Type the hostname or IP address of the destination host of the traceroute.

Advanced Options

Don't Resolve Addresses

  • To suppress the display of the hop hostnames along the path, select the check box.

  • To display the hop hostnames along the path, clear the check box.

Interface

From the list, select the interface on which traceroute packets are sent. If you select any, the traceroute requests are sent on all interfaces.

Time-to-Live

From the list, select the time-to-live (TTL) hop count for the traceroute request packet.

Type-of-Service

From the list, select the decimal value of the type-of-service (ToS) value to include in the IP header of the traceroute request packet.

Resolve AS Numbers

  • To display the autonomous system (AS) number of each intermediate hop between the device and the destination host, select the check box.

  • To suppress the display of the AS number of each intermediate hop between the device and the destination host, clear the check box.

Routing Instance

From the list, select the routing instance name for the ping attempt.

Gateway

Type the gateway IP address to route through.

Source Address

Type the source IP address of the outgoing traceroute packets.

Bypass Routing

  • To bypass the routing table and send the traceroute packets to hosts on the specified interface only, select the check box.

  • To route the traceroute packets by means of the routing table, clear the check box.

    If the routing table is not used, traceroute packets are sent only to hosts on the interface specified in the Interface box. If the host is not on that interface, traceroute responses are not sent.

Table 2: Ping Traceroute Results and Output Summary

Field

Function

Ping Traceroute Results and Output Summary

hop-number

Number of the hop (router) along the path.

host

Hostname, if available, or IP address of the router.

To suppress the display of the hostname, select the Don't Resolve Addresses check box.

ip-address

IP address of the router.

as-number

AS number of the router.

time1

Round-trip time between the sending of the first traceroute packet and the receiving of the corresponding Time Exceeded packet from that particular router.

time2

Round-trip time between the sending of the second traceroute packet and the receiving of the corresponding Time Exceeded packet from that particular router.

time3

Round-trip time between the sending of the third traceroute packet and the receiving of the corresponding Time Exceeded packet from that particular router.

Output = Complete path to the destination host not displayed

If the device does not display the complete path to the destination host, one of the following explanations might apply:

  • The host is not operational.

  • There are network connectivity problems between the device and the host.

  • The host, or a router along the path, might be configured to ignore ICMP traceroute messages.

  • The host, or a router along the path, might be configured with a firewall filter that blocks ICMP traceroute requests or ICMP time exceeded responses.

  • The value you selected in the Time Exceeded box was less than the number of hops in the path to the host. In this case, the host might reply with an ICMP error message.

For more information about ICMP, see RFC 792, Internet Control Message Protocol.

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