Facebook Outage: Yes, its DNS (sort of). A super quick analysis of what is going on., (Mon, Oct 4th)

This post was originally published on this site

For the Billions out there still wasting time on Facebook: Enjoy your increased productivity while many Facebook properties (Facebook, Instagram, WhatsApp) are down.

More readable summary of the analysis below: The BGP routes pointing traffic to Facebook's IP address space have been withdrawn. The Internet no longer knows where to find Facebook's IPs. One symptom is that DNS requests are failing. But this is just the result of Facebook hosting its DNS servers inside its own network. Even with working DNS (for example if you still have cached results), the IPs are currently not reachable

 

Here is a quick view of what may have happened.

1 – Does facebook.com resolve?

% host facebook.com
facebook.com has address 31.13.79.35
facebook.com has IPv6 address 2a03:2880:f141:82:face:b00c:0:25de
facebook.com mail is handled by 2560 smtpin.vvv.facebook.com.


% host www.facebook.com
www.facebook.com is an alias for star-mini.c10r.facebook.com.
star-mini.c10r.facebook.com has address 31.13.88.35
star-mini.c10r.facebook.com has IPv6 address 2a03:2880:f138:83:face:b00c:0:25de

Yes! (at least for me, it does). But was that just a cached response? Let's follow the DNS chain.

2. What is the NS record for facebook.com according to the .com zone?

(abbreviated output)

 

% dig NS facebook.com @h.gtld-servers.net

 

;; AUTHORITY SECTION: facebook.com. 172800 IN NS a.ns.facebook.com. facebook.com. 172800 IN NS b.ns.facebook.com. facebook.com. 172800 IN NS c.ns.facebook.com. facebook.com. 172800 IN NS d.ns.facebook.com. ;; ADDITIONAL SECTION: a.ns.facebook.com. 172800 IN A 129.134.30.12 a.ns.facebook.com. 172800 IN AAAA 2a03:2880:f0fc:c:face:b00c:0:35 b.ns.facebook.com. 172800 IN A 129.134.31.12 b.ns.facebook.com. 172800 IN AAAA 2a03:2880:f0fd:c:face:b00c:0:35 c.ns.facebook.com. 172800 IN A 185.89.218.12 c.ns.facebook.com. 172800 IN AAAA 2a03:2880:f1fc:c:face:b00c:0:35 d.ns.facebook.com. 172800 IN A 185.89.219.12 d.ns.facebook.com. 172800 IN AAAA 2a03:2880:f1fd:c:face:b00c:0:35

3. Let's use one of these NS records

% dig NS facebook.com @129.134.30.12
; <<>> DiG 9.10.6 <<>> NS facebook.com @129.134.30.12
;; global options: +cmd
;; connection timed out; no servers could be reached

4. So let's see why we can't reach these servers

% traceroute 129.134.30.12
traceroute to 129.134.30.12 (129.134.30.12), 64 hops max, 52 byte packets
 1  [redacted]  0.628 ms  0.159 ms  0.101 ms
 2  [redacted]  2.333 ms  1.715 ms  1.706 ms
 3  96.120.21.201 (96.120.21.201)  9.123 ms  10.691 ms  10.338 ms
 4  96.110.66.37 (96.110.66.37)  9.254 ms  8.754 ms  10.311 ms
 5  ae-13-ar02.westside.fl.jacksvil.comcast.net (68.86.168.1)  9.332 ms  11.930 ms  9.746 ms
 6  be-33622-cs02.56marietta.ga.ibone.comcast.net (96.110.43.117)  23.797 ms
 7  be-2112-pe12.56marietta.ga.ibone.comcast.net (96.110.33.178)  24.322 ms
 8  * * *

So Comcast doesn't know how to reach Facebook. Well… BGP should tell them

5. Let's check with a BGP Looking Glass

show router bgp routes 129.134.0.0/16 ipv4 hunt 
=============================================================================== 
BGP Router ID:4.69.178.225 AS:3356 Local AS:3356 
=============================================================================== 
Legend - 
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid 
l - leaked, x - stale, > - best, b - backup, p - purge 
Origin codes : i - IGP, e - EGP, ? - incomplete 

=============================================================================== 
BGP IPv4 Routes 
=============================================================================== 
No Matching Entries Found. 
===============================================================================

So looks like the route is gone. Oh well. Enjoy while it lasts.

 

 


Johannes B. Ullrich, Ph.D. , Dean of Research, SANS.edu
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(c) SANS Internet Storm Center. https://isc.sans.edu Creative Commons Attribution-Noncommercial 3.0 United States License.

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