An overview of OS support for IPv6 resolver distribution methods

In this post I will be going over the various levels of support for IPv6 resolver distribution for popular operating systems. Focus on desktop and mobile versions of OSes as those are the ones where we are usually automatically distributing resolver information. Dual stack is implied but IPv6 only functionality can be gleaned from said information as well.

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CCIE Lab Diary – EIGRP Lab

Overview/Goals

Implement EIGRP in a 9 router network with frame relay as the underlying L2 encapsulation to demonstrate protocol behaviours in a NBMA environment. Also involves tweaking of various parameters using summarization, redistribution, various stub types, distribute lists etc.

Technologies involved:

  • Serial interfaces
  • Ethernet interfaces
  • Frame Relay
  • EIGRP

Logical topology

eigrplab

Pitfalls/Things to watch out for

  • Frame Relay PVC issues
  • EIGRP timers on “slow” links, might want to tune them

CCIE Lab Diary – Layer 2 Lab

This is going to be a series of posts regarding the labs from the CCIE Routing and Switching class at UOIT.

I feel like these labs are complex enough for such posts to be interesting.

Overview/Goals

As the title of the post suggest this is a lab that incorporates various L2 technologies to implement.

Technologies involved:

  • Ethernet interfaces
  • Serial interfaces
  • VLANs
  • STP
  • LAGG (EtherChannel)
  • PPP with CHAP/PAP authentication
  • Frame Relay (ugh.)

Logical topology

l2lablogicaltopology

Pitfalls/Things to watch out for

  • The lab requires you to configure VLAN pruning on trunk links appropriately. Make sure to take a look at both the physical and logical topology to figure that out. Do this right the first time, you don’t want to backtrack later to fix issues with that later.
  • Frame relay is just as annoying as it was during the CCNA labs. Lack of practice with it does not help. Not all the DLCIs shown in the logical topology actually need to be used.

Ubuntu 14.04 Server and IPv6 Temporary Addresses

So, as we all know Ubuntu 14.04 was released today. I downloaded the server ISO to test in VirtualBox.

Let us see what we have here:

ss@trusty-testing:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04 LTS"

ss@trusty-testing:~$ ip -6 addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
 inet6 2001:470:1d:96b:70bb:7393:2071:faa2/64 scope global temporary dynamic
 valid_lft 597675sec preferred_lft 78675sec

Wait what? Am I going blind or is that an IPv6 temporary address [0] on a supposedly server image?

Investigating further:

ss@trusty-testing:~$ sudo sysctl -a | grep tempaddr
net.ipv6.conf.all.use_tempaddr = 2
net.ipv6.conf.default.use_tempaddr = 2
net.ipv6.conf.eth0.use_tempaddr = 2
net.ipv6.conf.lo.use_tempaddr = 2

What the hell? Not only did they leave temporary addresses turned on, they set the sysctl value at 2 which means that the system will prefer temporary addresses over standard ones for making connections. [1]

I asked around and apparently this is the case on Ubuntu 12.04 server as well.

ss@ubuntu-testing:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=12.04
DISTRIB_CODENAME=precise
DISTRIB_DESCRIPTION="Ubuntu 12.04.4 LTS"

ss@ubuntu-testing:~$ sudo sysctl -a | grep tempaddr
net.ipv6.conf.all.use_tempaddr = 2
net.ipv6.conf.default.use_tempaddr = 2
net.ipv6.conf.eth0.use_tempaddr = 2
net.ipv6.conf.lo.use_tempaddr = 2

So that is two LTS server releases with IPv6 temporary addresses turned on and set to 2.

Why are temporary addresses bad on a server?

Unpredictability – anything depending on source address validation. Even SLAAC addresses are more predictable because they can be calculated given the MAC address of the NIC.

Ideally, you should be configuring your server’s addresses statically. Leaving temporary addresses turned on on a server image is just a bad default.

References:
[0] – https://tools.ietf.org/html/rfc4941
[1] – http://ipv6int.net/systems/linux-ipv6.html#privacy