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These are general neworking-related posts. Archive for 2016.

IPv6 celebrates its 20th birthday by reaching 10 percent deployment

My latest Ars Technica IPv6 story is about IPv6 celebrating its 20th birthday and that it has reached 10% deployment at the end of 2015.

And the US is doing very well with almost 25% IPv6 deployment:

Read the article - posted 2016-01-04

Mixing IPv4 and IPv6 in BGP

When I first started running IPv6 over BGP, I ran into an interesting problem. The Cisco router I was working on had four full BGP feeds over IPv4. But when did show ip bgp, I noticed the router had five copies of each prefix. One of these paths had a really weird next hop address and was marked as unreachable.

Turned out those were IPv4 prefixes learned over an IPv6 BGP session.

Read the article - posted 2016-03-18

Cisco BGP identifiers

One of the tiebreakers in the BGP best path selection algorithm is to prefer the path learned from a BGP speaker with the lowest BGP identifier. So how are BGP identifier selected when they're not configured explicitly?

I always forget whether it's the highest or the lowest IP address configured on a Cisco router. Turns out this is remarkably hard to find in Google, but if you know where to look it's in Cisco's IOS command reference:

Permalink - posted 2016-04-22

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