[c-nsp] Quick routing question.

[Michael K. Smith - Adhost]

If I understand you correctly you are trying to ping from a host on your
network, not the directly connected router?  If you haven't turned up
BGP yet the return traffic is going to try to go back through the L3
network to your network because it's not yet receiving the
directly-connected route.  You will only be able to ping from the
directly connected router until you turn up BGP.

If I'm not understanding what you're trying to do just ignore me.  :-)

Mike

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Drew Weaver
> Sent: Thursday, September 09, 2010 10:10 AM
> To: 'Jon Lewis'
> Cc: cisco-nsp
> Subject: Re: [c-nsp] Quick routing question.
> 
> Hi,
> 
> 
> I assume the new connection doesn't have BGP turned up yet?
> --
> Correct, I am just trying to get it to where I can ping it first
(which is what I
> usually do, anyway).
> 
> 
> Ah...but when you do this, are you sure x.x.x.13 is really the other
side
> of your 10G connection?  This is ethernet, so when you try to ping
> x.x.x.13 from your router, it sees a route for x.x.x.12/30 via the 10G
> Level3 interface, and sends an arp request for x.x.x.13.  If Level3's
end isn't
> actually configured for the /30 you are, they're not going to reply to
> that arp...and maybe the x.x.x.13 you're looking for really is in use
> somewhere else on their network?
> --
> All valid points, when I trace route to .13 from the host that can
ping it I see:
> 
> [root at vmz bin]# tracert x.x.x.13
> traceroute to x.x.x.13 (x.x.x.13), 30 hops max, 40 byte packets
>  1  gw (gw)  0.486 ms  0.458 ms  0.463 ms
>  2  core (core)  0.460 ms  0.710 ms  0.709 ms
>  3  rtr (rtr)  0.427 ms  0.428 ms  0.425 ms
>  4  x.x.x.Level3.net (x.x.x.13)  3.238 ms  3.238 ms  3.236 ms
> 
> However, I can't know whether the return traffic is coming back in on
that
> connection, or not.
> 
> Are you redistributing x.x.x.12/30 into
> your IGP, or might those packets be going out the old connection?
> --
> Yes, and see above.
> 
> What's show ip arp on your router show you?
> --
> rtr#sh ip arp
> Protocol  Address          Age (min)  Hardware Addr   Type
Interface
> Internet  x.x.x.14              -   xxxx.xxxx.a9dc  ARPA
GigabitEthernet2/1/0
> Internet  x.x.x.13             14   xxxx.xxxx.4d7a  ARPA
GigabitEthernet2/1/0
> Internet  x.x.x.12              -   xxxx.xxxx.a9dc  ARPA
GigabitEthernet2/1/0
> 
> (Ignore the 'gigabit' part, on 12000s for some reason they never
changed the
> interface names).
> 
> thanks,
> -Drew
> 
> 
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