Tracert and Router interfaces

[FaithH]

When I'm doing a tracert and it outputs the hops with the IP addresses. Is this the IP address of the serial interface exiting the router? The loopback address? I'm trying to get a clear understand of where the IP address sits on the router (e0, s0, loopback, null).
~Faith~

 

[ccie9545]

RouterA(s0/0) ---(s0/0)RouterB(s0/1) --- s(0/0RouterC(s0/1)
e(e0/0) (e0/0)
| |
| |
You Host

If you are trace routing from <you> to <host> the first address will be e0/0 on RouterA then s0/0 on RouterB, the S0/0 on RouterC, then the address of the host.

Hope that helps....

Let me know if it makes sense or not.... Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com

 

[NewbieGirl]

Let me get this straight, all tracert will exit my local default gateway, then the next hop will be the entry point for the next router's s0 interface, then the next router's s0 interface, and so on. The last IP address on my tracrt will be the host's ip address.
Thanks,
Danielle

 

[FaithH]

So trace routing on a workstation will take the same hop as performing a trace routing while logon to a router? ~Faith~

 

[ccie9545]

in its basic form. There are times where the last IP address may not be the actual address that you are tracerouting to.

lets say that you are tracerouting to the ethernet address on RouterC in the previous diagram. In this case the last IP address would be the serial0/0 interface of routerC. This is because the destination IP address is local to RouterC, so RouterC responds.

The thing to remember is that traceroute is used to determine what hops are between you and the destination address. Knowing that, it will be the interface the source packet(you) is going to use to get to the destination at each hop.

Does that make sense.....if not let me know.... Erik Rudnick, CCIE No. 9545
mailto:erik@kuriosity.com

 

[marsd]

Faith,
&quot;..So trace routing on a workstation will take the same hop as performing a trace routing while logon to a router..&quot;

No, not necessarily. The idea is correct but a traceroute performed from a cisco router can be directed from any valid
(that is logically addressed) interface, from any number
of origin ports, with variability in setting ttl, wait intervals,etc..
The path(and therefore:=hops) your packet takes depends on too many variables to really give a pat answer to.

But basically no. A traceroute from a router will
not give you the same exact information.

Furthermore, tracert, the windows utility, is not
really compliant and may give you very different results in certain security scenarios.