plea for comcast/sprint handoff debug help

Wed Oct 28 13:18:17 UTC 2020

tl;dr:

comcast: does your 50.242.151.5 westin router receive the announcement
of 147.28.0.0/20 from sprint's westin router 144.232.9.61?

details:

3130 in the westin announces
  147.28.0.0/19 and
  147.28.0.0/20
to sprint, ntt, and the six
and we want to remove the /19

when we stop announcing the /19, a traceroute to comcast through sprint
dies at the handoff from sprint to comcast.

r0.sea#traceroute 73.47.196.134 source 147.28.7.1
Type escape sequence to abort.
Tracing the route to c-73-47-196-134.hsd1.ma.comcast.net (73.47.196.134)
VRF info: (vrf in name/id, vrf out name/id)
  1 r1.sea.rg.net (147.28.0.5) 0 msec 1 msec 0 msec
  2 sl-mpe50-sea-ge-0-0-3-0.sprintlink.net (144.232.9.61) [AS 1239] 1 msec 1 msec 0 msec
  3  *  *  * 
  4  *  *  * 
  5  *  *  * 
  6  *  *  *

this would 'normally' (i.e. when the /19 is announced) be

r0.sea#traceroute 73.47.196.134 source 147.28.7.1
Type escape sequence to abort.
Tracing the route to c-73-47-196-134.hsd1.ma.comcast.net (73.47.196.134)
VRF info: (vrf in name/id, vrf out name/id)
  1 r1.sea.rg.net (147.28.0.5) 0 msec 1 msec 0 msec
  2 sl-mpe50-sea-ge-0-0-3-0.sprintlink.net (144.232.9.61) [AS 1239] 1 msec 0 msec 1 msec
  3 be-207-pe02.seattle.wa.ibone.comcast.net (50.242.151.5) [AS 7922] 1 msec 0 msec 0 msec
  4 be-10847-cr01.seattle.wa.ibone.comcast.net (68.86.86.225) [AS 7922] 1 msec 1 msec 2 msec
  etc

specifically, when 147.28.0.0/19 is announced, traceroute from
147.28.7.2 through sprint works to comcast.  withdraw 147.28.0.0/19,
leaving only 147.28.0.0/20, and the traceroute enters sprint but fails
at the handoff to comcast.  Bad next-hop?  not propagated?  covid?
magic?

which is why we wonder what comcast (50.242.151.5) hears from sprint at
that handoff

note that, at the minute, both the /19 and the /20 are being announced,
as we want things to work.  so you will not be able to reproduce.

so, comcast, are you receiving the announcement of the /20 from sprint?
with a good next-hop?

randy