[c-nsp] Quick routing question.

[Heath Jones]

Have they correctly set their end of the link - does the IP address actually
match what you think it should be?
What does ARP say!!? ARP is the most underutilised tool for stuff like this!

I can see a scenario where downstream hosts could ping that IP, if they are
taking a different path and the ISP screwed up, and you could not because on
that router it will be taking the connected route. Only if there is another
path via another router - do a traceroute... Another option is they have an
egress filter on the new port that the replies hit, but not on the old one.
Are you not bringing up BGP on the new link? Does it just not work, or you
haven't configured it yet?

Turn on packet captuing for the new interface, bring the link down and up.
You should be able to see the gratuitous ARP packets (if you are not seeing
anything useful with show arp).


Heath




On 9 September 2010 17:35, Drew Weaver <drew.weaver at thenap.com> wrote:

> Howdy,
>
> I currently have two connections to Level3 because I am upgrading, one (the
> old one) is a 1Gbps connection in Router-1, the second one is a 10Gbps
> connection in Router-2.
>
> Both connections are up/up, the old connection is getting a full BGP
> session from Level3.
>
> I noticed that no matter what I do, I can't seem to ping Level3's side of
> our 10Gbps interface on the new connection from either of the 2 routers
>
> rtr#ping ip
> Target IP address: x.x.x.13
> Repeat count [5]:
> Datagram size [100]:
> Timeout in seconds [2]:
> Extended commands [n]: y
> Source address or interface: x.x.x.14
> Type of service [0]:
> Set DF bit in IP header? [no]:
> Validate reply data? [no]:
> Data pattern [0xABCD]:
> Loose, Strict, Record, Timestamp, Verbose[none]:
> Sweep range of sizes [n]:
> Type escape sequence to abort.
> Sending 5, 100-byte ICMP Echos to x.x.x.13, timeout is 2 seconds:
> .....
> Success rate is 0 percent (0/5)
>
> I am able to ping their side of the interface from hosts downstream from
> the routers, just not the routers themselves.
>
> [root at vmz ~]# ping x.x.x.13
> PING x.x.x.13 (x.x.x.13) 56(84) bytes of data.
> 64 bytes from x.x.x.13: icmp_seq=1 ttl=60 time=3.27 ms
> 64 bytes from x.x.x.13: icmp_seq=2 ttl=60 time=14.9 ms
> 64 bytes from x.x.x.13: icmp_seq=3 ttl=60 time=3.01 ms
> 64 bytes from x.x.x.13: icmp_seq=4 ttl=60 time=3.19 ms
> 64 bytes from x.x.x.13: icmp_seq=5 ttl=60 time=3.10 ms
>
> I can't really think of any reason why I wouldn't be able to ping their end
> of the Interface from this router, connectivity is obviously good
> considering I can ping it from a host downstream from the router.
>
> Is anyone aware of any sort of gotcha when doing something like this?
>
> -Drew
>
>
>
>
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