IPv6 Source Address Selection

As we all know an IPv6 enabled host can have multiple addresses. In order to select a source address for a to-be established outbound connection, operating systems implement a source address selection mechanism that evaluates multiple source address candidates and selects the (potentially) best candidate. Criteria for this selection are defined in RFC6724 (which obsoletes RFC 3484).

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CVE-2016-1409 – IPv6 NDP DoS Vulnerability in Cisco Software

Dear readers,

As you may have already noticed, Cisco released an urgent security advisory describing an IPv6 Neighbor Discovery DoS Vulnerability in several flavors of Cisco’s operating systems. Currently IOS-XR, XE and NX-OS are affected while ASA and “classic” IOS are under investigation. At first glance, it might look like yet another IPv6 DoS vulnerability. Looking closer, Cisco is mentioning an unauthenticated, remote attacker due to insufficient processing logic for crafted IPv6 NDP packets that are sent to an affected device. Following the public discussion about the vulnerability, it seems that these packets will reach the, probably low rate-limited, LPTS filter/queue on IOS XR devices “crowding” out legitimate NDP packets resulting in a DoS for IPv6 traffic, or in general a high CPU load as these packets will be processed by the CPU. More details are currently not available, but this might indicate the affected systems aren’t doing proper message validation checks on NDP packets (in addition to the LPTS filter/queue problem).

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The Beauty of IPv6 Link-Local Addressing. Not

In November 2014, after quite some controversy in the IETF OPSEC working group (for those interested look at the archives), the Informational RFC 7404 “Using Only Link-Local Addressing inside an IPv6 Network” was published. It is authored by Michael Behringer and Eric Vyncke and discusses the advantages & disadvantages of an approach using “only link-local addresses on infrastructure links between routers”.

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Tools for Troubleshooting and Monitoring IPv6 Networks

Yet another interesting 180-minute workshop in IPv6 Security Summit of TROOPERS16, which aimed to introduce the IPv6 troubleshooting and monitoring tools, which are essentially needed by users in order to know how to deal with IPv6 in any IPv6-enabled network.

Before we dive into this post, let me introduce you in few words “Gabriel Müller” the speaker and the instructor of this workshop. Gabriel works as a senior consultant at AWK Group by mainly assisting clients in the public and private sectors as a project manager and an expert in the network area.

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