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Ypsilanti, MI

Routing Change in SE Mich.: No more router hostnames

See hops 2, 3, 6.
In addition to recent increasing congestion between Comcast and major CDNs/peers (Level 3 and Google, specifically), I've observed a major change in their routing architecture.

Area routers no longer resolve hostnames, making it very difficult to discern where my traffic goes for crucial steps in the route. According to the screenshot I post here, they appear to be obscuring a crucial router completely in hop 6. Anyone know anything about this?

Carpentersville, IL
Not sure if its the same thing, but if I do a trace to www.msu.edu, I get a few hops with no information.

I actually thought there was some kind of setting in the routers or switches along the way that either blocked (or maybe the better word is turned off) ICMP requests (like ping, nslookup, etc). If that's the case, sure it sucks to try to troubleshoot something, but I don't see it as an abnormal or drastic change to how things work.


--Brian Plencner

E-Mail: CoasterBrian72Cancer@gmail.com
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Ypsilanti, MI
Hop 14 (in your trace) has always timed out (MSU's Intrusion Prevention System architecture, if I remember right). Hop 6, which sits between two Comcast IP addresses, never used to. Also, look at your hops 3 and 4. They help you determine your area router's architecture (namely, that there are 10GigE ports between you and hop 10). The same routers in my area now have no DNS resolution for some reason. That's what I'm trying to figure out!

That VoIP Guy
East Lansing, MI
reply to johnnn
Your hop #6 is the hand-off between Comcast and Merit at the Gigapop in Chicago. That router is not currently processing ICMP traffic since they turned on IPv6 a few months ago. Everybody should be seeing the same. It is processing traffic normally otherwise.

Hop #9 is the handoff between Merit and MSU's core infrastructure. It's not an IDP or firewall, but I believe they turned off ICMP processing on the external interface of that Juniper as well. Again, not processing ICMP (pings) is not a big deal.

I wouldn't count MSU a major CDN or peer. We are a part of the peering circle at the Gigapop, but we are hardly major. We have a single 10Gb connection in that direction (10gb in other directions as well, but this would be the one that Comcast peers with us).

Comcast has been changing their local infrastructural to make things more decentralized as of late. This is a good thing. As short as 5 years ago there was a sizable portion of traffic they still backhauled to the Denver area for regular commodity traffic. For those of us in Michigan, Chicago is still the favorite hand-off.

Next Year Again..

Chicago, IL
·AT&T U-Verse

1 edit
reply to johnnn
Mines here in Chicago has just the #9 hop not respond. Nice latency though.

Tracing route to www.msu.edu []
over a maximum of 30 hops:

1 4 ms 2 ms 1 ms []
2 32 ms 25 ms 25 ms c-71-239-72-1.hsd1.il.comcast.net []
3 16 ms 11 ms 37 ms te-2-5-ur02.chicago201.il.chicago.comcast.net []
4 16 ms 11 ms 23 ms te-0-6-0-7-ar01.area4.il.chicago.comcast.net []
5 15 ms 18 ms 23 ms he-3-11-0-0-cr01.350ecermak.il.ibone.comcast.net []
6 13 ms 11 ms 14 ms pos-1-2-0-0-pe01.350ecermak.il.ibone.comcast.net []
7 15 ms 11 ms 43 ms
8 32 ms 26 ms 19 ms vlanx58.msu9.mich.net []
9 * * * Request timed out.
10 31 ms 20 ms 19 ms core-srx-xe000-1.net.msu.edu []
11 25 ms 64 ms 23 ms core-mx-xe220-1.net.msu.edu []
12 23 ms 22 ms 20 ms dc-core-fw-v1012.net.msu.edu []
13 22 ms 23 ms 31 ms www.msu.edu []

Trace complete.


Ypsilanti, MI
reply to quetwo
Thanks for the awesome information. I'll make sure not to assume stuff! I don't mind that Chicago is the favorite handoff (although I know Merit and Comcast are directly peered elsewhere). It's the fact that hops 2 and 3 (in my original trace) no longer resolve DNS that bothers me. Maybe it's a temporary change, but any step that reduces transparency to the end user, IMHO, isn't a good one!


united state
I've noticed slowdowns, no RDNS and RDNS additions in the last week or so. I'm guessing some equipment upgrades.

Specifically my route to Atlanta shows a new XE interface from GR to Pontiac (hop 5).

Also on my Chicago route I have an additional local hop (hop 5):


Ypsilanti, MI
Click for full size
Tracing in the other direction shows an he interface in Pontiac and an xe interface in west Ann Arbor. I know routes aren't the same in each direction, so this may be useless information.


reply to johnnn
Maybe someone recently updated that router and forgot to put the name on it? I'm seeing the same thing you are without resolving a name on that specific router, but all of the others leading up to it have names.