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Why You're Having Problems Reaching DSLReports (and Other Sites)

If you've been having problems accessing DSLReports.com and a flood of other websites this week, you're not alone. The problem, as it turns out, was experienced by tier-one and last mile ISPs alike across much of North America. The cause? Border Gateway Protocol (BGP) routing tables this week finally became too large for some top-level Internet routers to handle, resulting in those routers being unable to manage the Internet's traffic.

Our hosting provider LiquidWeb was similarly impacted, and discussed the problems on Twitter (most users should no longer be having problems). A blog post over at Renesys offers some excellent detail into what occurred, calling this "more of an annoyance than a real Internet-wide threat":

quote:
There was minor consternation in Internet engineering circles today, as the number of IPv4 networks worldwide briefly touched another magic “power of 2″ size limit. As it turns out, 512K (524,288 to be exact, or 2-to-the-19th power) is the maximum number of routes supported by the default TCAM configuration on certain aging hardware platforms.
Some additional excellent explanations can be found at BGPMon, which notes that Verizon quite unintentionally caused the ripple effect across un-upgraded routers:
quote:
Looking at the our data we quickly see that the new prefixes being announced at that time were almost all originated by the Verizon Autonomous systems 701 and 705. All of the new routing entries appear to be more specific announcements for their larger aggregate blocks. For example BGPmon detected 170 more specific /24 routes for the larger 72.69.0.0/16 block.

So whatever happened internally at Verizon caused aggregation for these prefixes to fail which resulted in the introduction of thousands of new /24 routes into the global routing table. This caused the routing table to temporarily reach 515,000 prefixes and that caused issues for older Cisco routers.
The problem isn't insurmountable: older Cisco gear for example can have the 512,000 route limitation increased. It's worth noting that some engineers saw this problem coming back in May.

Most recommended from 40 comments



firephoto
Truth and reality matters
Premium Member
join:2003-03-18
Brewster, WA

2 recommendations

firephoto

Premium Member

Profit vs infrastructure

Making money is more important than upgrading aging hardware that is so costly it's probably been paid for 100 times over it's life so far. And these are the literally the pillars of the internet, imagine how old those ISP edge routers that the shills like to cry about their costs all the time.

It's always the money.

hello123454
Premium Member
join:2002-02-02
21845

2 recommendations

hello123454

Premium Member

Proactive much?

So they saw this issue back in May? Why didn't they see this issue back in 2000? You can't make this stuff up.
floydb1982
join:2004-08-25
Kent, WA

2 recommendations

floydb1982

Member

Simply upgrade to IPv6

Upgrade to IPv6 and the problem is solved.