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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.
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Auto playing videos

Usually don’t do posts like these but..

Twitter, Facebook, $SOCIALNETWORKINGSITE:

Auto playing videos are stupid.

  • You are wasting my bandwidth and yours
  • If I wanted to see the video, I would you know..click it and watch it. What a novel concept.

Stop. doing. them.

I do not care if it is the cutest cat video this side of the Milky Way or a horrifying video of a journalist being shot. Just stop.

Thanks,
An Internet user who knows how to click things he wants to watch.

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Adiós self-hosted mail server

As the title suggests, I will be retiring my self-hosted mail server (mx1.staticsafe.ca) soon, most likely by next month.

It has been a lot of fun and an excellent learning experience but I simply cannot devote the time and/or effort into active maintenance of the server.

I am moving all of the mailing lists that I used this server for to the extremely competent folks over at Fastmail.

The retirement will be done in a few stages as follows:

  1. Stage 1 – Personal mailing list subscription move (completed)
  2. Stage 2 – Change of MX, SPF records for staticsafe.ca to Fastmail’s servers and add a wildcard alias there.
  3. Stage 3 – Discontinuation of relay/non-personal services on mx1.staticsafe.ca. One person is using this server as a submission relay for their server. I will be asking them to move to my new MSA only server. Services for caffeine-linux.org will also have to be discontinued.
  4. Stage 4 – Stop all relevant daemons. Postfix, Dovecot, amavisd-new.

My Thanks

A lot of people and/or companies have provided direct and/or indirect support for this learning experience.

  • Linode Library for providing initial inspiration for the current configuration of the server
  • The folks in the Postfix and Dovecot communities. (#postfix, postfix-users, #dovecot, Wietse for the wonderful software)
  • purrdeta for telling me mail servers are a lot of fun

Addendum

I have put my server configuration files on Github if anyone is interested, you can see them here.

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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