Home > Networking > Originating IP address

Originating IP address

More work securing the network. I was setting up RADIUS authentication and authorization using the Network Policy Server role of Windows 2008 R2 (that will be another post). Here is a simplified network diagram.

Everything worked perfectly for the local router (rtr01) and switch (sw01) so it was time to do the same on the remote devices. I started with the switch (sw02) and then moved onto the router (rtr02) when I ran into problems. I couldn’t log into the router. I tried the router’s local username which did work indicating the router couldn’t authenticate against the RADIUS server. This seemed very odd to me since the switch, which is further away, worked perfectly. I tried a simple ping to the server and it failed. Now I was really confused, because the switch could ping the server but the router couldn’t.

At this point I’m thinking it’s some strange configuration setting on the router so I fire up Google and start searching. I come across the Cisco Extended Ping and Traceroute commands as well as a short statement indicating the originating address is the IP of the interface the packet leaves. So I try an Extended Traceroute using an originating address of and it works. This means that a reverse route from the server to the subnet doesn’t exist. Adding the following route to sw01 fixed the problem:

ip route

Switch sw01 already had a route to the network. Until now there was never a need to know how to get to the WAN interfaces of the routers.

Categories: Networking Tags: ,
  1. May 11, 2013 at 2:46 PM

    Thanks for finally talking about >Originating IP address | Chuck’s Blog <Loved it!

  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: