cold-potato at L3/Chi into UU?

Bradley Urberg Carlson buc at
Sat Jan 6 19:51:00 UTC 2007

In Chicago, L3 appears to be routing some traffic to UU directly, but 
for some other UU destinations, L3 is handing-off to UU via New York:

trace from L3/Chi to (AS8015 via 701) is carried to UU via 
New York (edited):

>  1 ( 8 msec
>   2 ( 20 msec
>   4 ( 20 msec
>   8 visi-gw.customer.ALTER.NET ( [AS701 {ALTERNET}] 32 
> msec

Oddly, a L3/Chi trace to the last hop above within AS701 ( 
enters UU immediately in Chicago, taking the shorter path to 

>  1 ( 0 msec
>  2 ( [AS701 {ALTERNET}] 
> 0 msec
>  6 visi-gw.customer.ALTER.NET ( [AS701 {ALTERNET}]  8 msec

UU support has verified that AS8015 prefixes are advertised at UU's 
L3/Chi peering point; and L3 support reports this is "routing as 
designed".   I would guess that UU requires its peers to use hot-potato 
routing, so I'm at a loss as to what kind of traffic engineering is 
being used.

Bradley Urberg-Carlson
VISI Network Operations; pgp keys avaialble at

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