IPV6 in enterprise best practices/white papers

From time to time I look what's going on on a Nanog mailing list. It is a very interesting mailing list in which quite often something very interesting pops up. You don't have to sign to this mailing list in order to see posts, there are publicly available archives, which might be a better option for those sporadically looking at this list. This time my eye caught a thread with the subject line as in the title of this post. So, since IPv6 is hot topic these days, or at least it seems so, I decided to read through this thread and make summary along with pointers to materials that were linked to.

The thread was started on January 26th, 2013. by Pavel Dimow who asked for a real world example of IPv6 deployment in enterprise. More specifically, he said that he thinks that the procedure to introduce IPv6 is:

1. Create address plan.
2. Implement security on routers/switches and then hosts.
3. Create AAAA and PTR records in DNS.
4. Configure DCHPv6.
5. Test IPv6 in LAN.
6. Configure BGP with ISP.

He also wondered how to maintain PTR records in case SLAAC or DHCPv6 is used and should he use DDNS for that purpose. Finally, he asked weather to use SLAAC or DHCPv6.

The general consensus of repliers was that first IPv6 connectivity to the Internet should be established. The reason is that operating systems prefer IPv6 over IPv4 and if there is AAAA record, along with localy assigned IPv6 address, then IPv6 connection will be first established. Since, if you configure Internet connectivity as a last step, there is no path to destination, timeouts will have to expire in order to detect missing IPv6 connectivity and in the end users will experience delays. This scenario actually happened in one network I used. Namely, intranet Web server was given IPv6 address to test that IPv6 worked.  Since all operating systems today have IPv6 enabled by default clients on a local network tried to connect to Web server using IPv6 which wasn't possible since only a small part of intranet got IPv6 connectivity. Still, it turns out that it is possible to configure address preferences in an OS (though, I don't know which ones yet). And, there is a draft that defines how address preferences can be distributed via DHCPv6.

After obtaining addresses from ISP and making address plan the next step would be to configure network equipment, preferably not everything, something for testing. Very important is to get at least some experience with IPv6 before deploying it in a production environment. To get experience there are tunnel broker services that are free and very good. HE.net apparetnly also allows free IPv6 BGP connectivity via tunnels.

Here is more specific series of steps to introduce IPv6. This one was written by a person doing an actual deployment. Note that deployer had its own ASN:

• get a /48 PI from the local LIR
• configure the border routers to announce the prefix and do connectivity tests (ping Google/Facebook addresses using an IPv6 address from our own /48 - loopback on the router)
• configure IPv6 addresses on internal router and do connectivity tests again
• configure firewall interfaces with IPv6 addresses and again connectivity tests
• configure IPv6 firewall rules (mostly a mirror of the IPv4 rulesets)
• configure IPv6 address on DMZ servers (actually the first one configured were the DNS servers)
• do connectivity tests again
• publish IPv6 records for the DNS servers and for the domain and run ping/telnet 80 tests from another ipv6 enabled network to check that everything is OK.
• publish AAAA records for all the hosts in the DMZ and making sure all the services available on IPv4 were also available on IPv6
• did the same for the servers in the "Server network"
• last step was to enable IPv6 on the network that served the users using RA with the stateful configuration bit set on the firewall and DHCPv6 to serve up DNS servers for IPv6

Security is very important aspect in any network, so it is in IPv6, too. Some of the IPv4 security mechanisms translate to IPv6 security, e.g. DHCP snooping, but there are some IPv6 specific things to be aware of, like RAs.

Scalability is other very important aspect of any network. There was subthread about snooping MLD, or lack of snooping. Namely, there are high density VM deployments in which even high end switches don't have enough processing/storage power. In that case, multicasting degrades to broadcasting. In one post a poster asked about some figures from real world switches, e.g. maximum number of multicast groups, but unfortunately, there was no answer.

Finally, very good source of different documentation about IPv6 deployment is Internet Society's Deploy360 pages. There are documents that describes how to develop address plan and Aaron Hughes presentation from NANOG.

How to change Volume Group's name...

In default installation of CentOS LVM is used and all volume groups are named VolGroup00. This can create problems when multiple machines' disks have to be accessed from a single machine. So, one of the options is to rename volume groups. This is actually very easy to do in the following four steps that can be done on a live machine:

1. Rename volume group.

# vgrename VolGroup00 <newname>

2. Change /etc/fstab

Open it in some text editor and do a search and replace through the file, i.e. any occurrence of VolGroup00 change to <newname>.

3. Change /etc/boot/grub.conf

Open it in some text editor and do a search and replace through the file, i.e. any occurrence of VolGroup00 change to <newname>.

4. Recreate initrd image.
First, rename old initrd image. initrd images are in /boot directory and their name contains the version of currently running kernel (use uname -r but without architecture part).

# initrd <initrdname> <kernel version>

Be careful that you don't have newer kernel installed which will be started during the next boot process. In that case you'll have problems! Maybe it's best to restart machine before doing this whole procedure.

Restart machine and that should be it. :) Of course, just to be safe try this first on some test machine.

Using ~ as a shortcut for home directory...

I just stumbled on the question why tilde (~) is used as a shortcut for home directory on Unix. It's very interesting since it never occurred to me to ask this question? :)

Then, there are lot more questions like that one on StackExchange, here is a selection of some interesting ones (to me at least):

• Why is . and .. used for current and parent directories. The answer isn't so clear as for tilde, but it turned out that hidden files (those whose name begins with a dot) are actually consequence of a bug in early versions of ls command (source and Wikipedia page).
• What does /etc mean?
• What was the shell used before Bourne shell?
• Why is dash (-) used to denote options?
• Why isn't umount spelled unmount?
• What is the origin of 'root' account? But note that this question isn't definitely resolved.
• What is the origin of wheel group name?

And, for the end, here is why vi uses hjkl for cursor movement.