Cisco and APIPA

tcp/udp

I haven't seen this IP address range mentioned on any Cisco related material. I am talking about 169.254.0.1 through 169.254.255.254. Technically, that would be a private range, right?
How does Cisco look at it? --both on exams, and IOS/equipment.


For a definition of APIPA, click below:

http://www.webopedia.com/TERM/A/APIPA.html

blackmage439

I remember it being in the material. I can't recall what course it was in, but I know APIPA was mentioned specifically.

dtlokee

APIPA is not an RFC 1918 private range, it is a public range (rumor was Bill Gates had the address allocation and it was later used by the IETF as the link-local address range for IPv4), but because it does not configure a default gateway it cannot route to any other subnet, and therfore can not be used to connect to the Internet via a Cisco router(Windows has ICS which can use APIPA). As a result this makes it a "private range" because it cannot connect to any other network, similar to using a public range on a network which is not connected to the Internet, it is still a public range with no way to connect to the public network. Host autoconfiguration was mentioned in RFC 3330 (using the 169.254.x.x block) but there was no specific directions on how it should be done, the Microsoft implementation of this is what they call APIPA and is only used when a DHCP server is not available (this would explain the lack of APIPA topics in the Cisco courses). The newer RFC 3927 details "Dynamic configuration of IPv4 Link Local addresses" aka addresses that can only be used on the subet and are not routable, which is similar to the concept in IPv6 with link locak addrsses (the FE80: prefix)

HTH