Ping an internal interface of a router

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Created by: Usman Khan on 03-01-2014 01:48:01 AM
Hi,

I need to access internal interfaces of the router, I am trying to ping it from Linux commandline but it doesnt look like its routable. Is there a way to ping internal interfaces from Linux or not.

Thanks
Usman

Subject: RE: Ping an internal interface of a router
Replied by: Joseph Clarke on 03-01-2014 09:06:31 AM
You'll need to add static routes on the Linux side as well as perhaps static routes on the IOSv side (if the router is not directly connected to the Linux host).  Assuming 10.20.10.110 is the IP address of the router that is in the same subnet as the Linux host, and you want to ping 10.20.20.110 on this same router, then on the Linux host, execute:

sudo route add -net 10.20.20.0/24 gw 10.20.10.110

Since you're pinging the same router, you won't need an additional route on the IOSv side.  The ping should just work at this point.

Subject: RE: Ping an internal interface of a router
Replied by: Joseph Clarke on 03-01-2014 01:52:03 PM
The interfaces should only be X/Y not X/Y/Z.  I assume you mean Gi0/1...

In any event, it would be helpful if you would post the output of "ifconfig -a" from the Linux host and show run from the IOSv instance with which you're having problems.

For routing outside the AiO, you should have (assuming you're using 3node) an interface plummed on a 172 subnet or something that is private to your VM host.  In my case, I am using the AiO VM in Fusion on Mac OS X.  My 3node routers each have an interface in the 172.16.129.0/24 subnet that is plummed on my Mac and private to my Mac only.  Using this interface, my Mac can ping the IOSv instances (all of them) directly.

Subject: RE: Ping an internal interface of a router
Replied by: Usman Khan on 03-01-2014 03:49:40 PM
Hi Joseph, yes I meant ge0/1 and before I get you all my config and route -a info, I have a follow up question that might clear up things for me. In the 3node example, I cannot figure out which one is the mgmt interface? All the interfaces seem like they are routing interfaces. Also, how is for example ge0/3 getting my linux interfaces' subnet IP? Does it automatically detect that?

Subject: RE: Ping an internal interface of a router
Replied by: Usman Khan on 03-01-2014 01:06:14 PM
Hi Joseph, thanks for the quick comment. The problem is that although my linux interface and router's interface are on the same subnet, but they still are not able to ping each other. When I say "router's interface" please keep in mind it is the ge0/0/1 I am talking about. NOT management interface. Also, my ge0/0/1 is not visible outside the all-in-one-VM. Is there a way to make them visible outside? I can see ext ip for mgmt interface but not routing interfaces. 

Subject: RE: Ping an internal interface of a router
Replied by: Joseph Clarke on 03-01-2014 06:05:43 PM
There is no set "management" interface.  All interfaces with an IP address can be used for management.  I typically use the one connected to the AiO VM (for me that's 10.20.10.0/24 and by default it's 10.10.10.0/24).  But the 172 address will also work.

Assuming you mean Gi0/3 on Router1, this interface is assigned its IP via DHCP from the VM host (e.g., my Mac in my case).  The AiO VM will get a virtual interface in this same subnet.  The interface will be called vb_ex_eth1.  This is the external ethernet interface used for both the IOSv instances on the AiO VM.  If you open the EmulatorUserGuide on the AiO desktop, you will see a topology diagram of 3node.  The lan_ex bus at the top of the diagram is this external LAN that the AiO, IOSv, and the VM host can access.  For simplicity sake, you can consider this a good management IP for all IOSv instances.

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