traceroute question

[chestermccarter]

when doing a traceroute from a router, where does it get the router name information if there is no dns server in the router config?

[Harold Ritter]

It is possible that the router gets it from a local ip address to host mapping created by using the "ip host " command.

Let me know if I answered your question,

[chestermccarter]

thanks but no luck.

Here's the whole story:

We have a router in SLC, when I do a trace route to another site it returns the correct ip addresses but 2 of the intermediate routers are misnamed. There is no dns server defined on the SLC router and no host mapping either. We've verified that our official DNS servers are correct. Is it possible that there is a rogue dns server on the local lan? but how would the router know to use it?

[Harold Ritter · Accepted solution]

Bear in mind that if "ip domain-lookup" is configured and no DNS is, the router will send DNS lookup requests out of all interfaces using 255.255.255.255 as the destination address. If any DNS is directly connected to these interfaces of some other router connected to these interfaces is configured with a helper address, the DNS lookup requests my get to a DNS server.

Let me know if I answered your question,

[chestermccarter]

that solves that problem... no idea that the router would broadcast a dns request. thanks

configuring no ip domain-lookup fixes the issue