Learn for Free

Not just technical skills...


Coursera is one of my favorite places to learn a new topic or even expand my horizons on topics with which I am already familiar.  The pacing of a real class structure, with weekly lectures and homework, applies just enough pressure to keep me motivated throughout the class and permits just enough flexibility to fit it into my real-life schedule.

Coursera is an education platform that partners with top universities and organizations worldwide, to offer courses online for anyone to take, for free.

https://www.coursera.org/




I believe this is a trend we will continue to advance as more and more colleges and universities open up classes for free.

Open.Michigan is a University of Michigan initiative that enables faculty, students, and others to share their educational resources and research with the global learning community.

http://open.umich.edu/

Software Defined Networking (SDN) class at Coursera

Looking forward to this class starting May 25th, 2015:

https://www.coursera.org/course/sdn

Software Defined Networking

About the Course

This course introduces software defined networking, an emerging paradigm in computer networking that allows a logically centralized software program to control the behavior of an entire network. 

Separating a network's control logic from the underlying physical routers and switches that forward traffic allows network operators to write high-level control programs that specify the behavior of an entire network, in contrast to conventional networks, whereby network operators must codify functionality in terms of low-level device configuration. 

Logically centralized network control makes it possible for operators to specify more complex tasks that involve integrating many disjoint network functions (e.g., security, resource control, prioritization) into a single control framework, allowing network operators to create more sophisticated policies, and making network configurations easier to configure, manage, troubleshoot, and debug.

Enabling IPv6 on CentOS 5.6

Some additional information about IPv6 support and configuration is available from the CentOS wiki at:
http://wiki.centos.org/FAQ/CentOS5
These are the steps I followed to get IPv6 to work.
Edit the network file:
vi /etc/sysconfig/network
Set IPv6 networking to ‘yes’:
NETWORKING_IPV6=yes
Exit and save these changes.

Option 1, EUI-64 auto-assigned IPv6 address:

Edit the interface file:
vi /etc/sysconfig/network-scripts/ifcfg-eth0
If you want to have an auto-assigned IPv6 address based on EUI-64 auto-configuration:
DEVICE=eth0 ONBOOT=yes BOOTPROTO=none HWADDR=00:13:21:0D:0D:B9 # Required for EUI-64 auto addressing. DHCP_HOSTNAME=v6LAB-WWW1.opr.test.statefarm.org IPV6INIT=yes # Enables IPv6 addressing on interface. IPV6_AUTOCONF=yes # Enables EUI 64 auto-addressing. #IPV6ADDR= #IPV6_DEFAULTGW=
HWADDR and DHCP_HOSTNAME should be updated to match the specifics of each server but is likely automatically configured from install.
Exit and save these changes.

Option 2, static IPv6 address:

Edit the interface file:
vi /etc/sysconfig/network-scripts/ifcfg-eth0
So it the file should look something like this:
DEVICE=eth0 ONBOOT=yes BOOTPROTO=none HWADDR=00:13:21:0D:0D:B9 # Required for EUI-64 auto addressing. # Optional for static. DHCP_HOSTNAME=v6LAB-WWW1.opr.test.statefarm.org IPV6INIT=yes # Enables IPv6 addressing on interface. IPV6_AUTOCONF=no IPV6ADDR=AAAA::260:3EFF:FE11:5001 IPV6_DEFAULTGW=AAAA::260:3EFF:FE11:6780
HWADDR, DHCP_HOSTNAME , IP6ADDR, and IPV6_DEFAULTGW should be updated to match the specifics of each server.
Exit and save these changes.
Restart the interfaces with the new options:
service network restart
If there is no error message, IPv6 setup is complete. Jump to IPv6 Test and Validation.
If you get this kernel error:
CRITICAL : [ipv6_test] Kernel is not compiled with IPv6 support
See the section for Enabling IPv6 on CentOS 5.6 Kernal (if needed).

Enabling IPv6 on CentOS 5.6 Kernal (if needed)

The kernel options to support IPv6 on the Ethernet modules need to be enabled. Edit the module probe configuration file:
vi /etc/modprobe.conf
Search for these two lines and comment them out if they exist:
#alias net-pf-10 off #alias ipv6 off
And change this one from ‘1’ to ‘0’:
options ipv6 disable=0
So these lines look like this:
#Uncomment the next two lines to disable IPv6 support at boot. #alias net-pf-10 off #alias ipv6 off #Swap commented/uncommented lines below to disable IPv6 support at boot. #options ipv6 disable=1 options ipv6 disable=0
The only way for the new module options to take place is by a reboot:
shutdown –r now

IPv6 Test and Validation

With IPv6 enabled, we can confirm the interface has at least two IPv6 addresses. A global and a link(local) address:
[root@v6LAB-W1 ~]# ifconfig eth0 Link encap:Ethernet HWaddr 00:13:21:0D:0D:B9 inet6 addr: aaaa::213:21ff:fe0d:db9/64 Scope:Global inet6 addr: fe80::213:21ff:fe0d:db9/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:63 errors:0 dropped:0 overruns:0 frame:0 TX packets:96 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:6813 (6.6 KiB) TX bytes:15909 (15.5 KiB) Interrupt:209 Memory:fdef0000-fdf00000
We can ping the router (like Windows, the command is ping6):
[root@v6LAB-W1 ~]# ping6 aaaa::260:3eff:fe11:6780 PING aaaa::260:3eff:fe11:6780(aaaa::260:3eff:fe11:6780) 56 data bytes 64 bytes from aaaa::260:3eff:fe11:6780: icmp_seq=0 ttl=64 time=0.594 ms 64 bytes from aaaa::260:3eff:fe11:6780: icmp_seq=1 ttl=64 time=0.541 ms 64 bytes from aaaa::260:3eff:fe11:6780: icmp_seq=2 ttl=64 time=0.529 ms 64 bytes from aaaa::260:3eff:fe11:6780: icmp_seq=3 ttl=64 time=0.546 ms --- aaaa::260:3eff:fe11:6780 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3001ms rtt min/avg/max/mdev = 0.529/0.552/0.594/0.034 ms, pipe 2 [root@v6LAB-W1 ~]#
If we console into the router, we can ping our new server:
v6LAB-R1# v6LAB-R1#ping aaaa::213:21ff:fe0d:db9 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to AAAA::213:21FF:FE0D:DB9, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/4 ms v6LAB-R1#
And ssh to it:
v6LAB-R1# v6LAB-R1#ssh -l root aaaa::213:21ff:fe0d:db9 Password: Last login: Wed May 25 05:48:50 2011 from localhost6.localdomain6 [root@v6LAB-W1 ~]# [root@v6LAB-W1 ~]#

Apache/HTTPD configuration

No special configuration is necessary to enable IPv6 requests on Apache.
After installing Apache, it needs to be set to start at boot using this command:
[root@v6LAB-W1 ~]#chkconfig --level 2345 httpd on

Tweet forwarded by @russruns

cmross: Will seek this out later today.  Steve Jobs banner in the Windy City a nice tribute http://t.co/UjlQ2eG0 via @zite
Original Tweet: http://twitter.com/cmross/status/123434197460324352
Sent via TweetDeck (www.tweetdeck.com)

F5 LTM GTM IPv6 quick hit

Just quick note, F5 products LTM and GTM work just great with IPv6.  But IPv6 address shortening (double-colons '::') is not permitted in the GUI or tmsh.
LTM and GTM are Linux based systems, so if you are using BASH, the standard rules apply.
But if you are using the GUI or tmsh, IPv6 addresses must be fully completed.
This:
fe80:0:0:0:201:d7ff:fed4:d041
Not this:
fe80::201:d7ff:fed4:d041     ^^  Cannot have a double colon.

IPv6 SLAAC(er)

Promoted as a feature of IPv6, allows a device to connect to a network and receive an addresses without the administrative overhead of managing a DHCP.

But there are a few limitations that limit its usefulness in an enterprise environment:

• SLAAC only works with /64 subnets. No more, no less.
• SLAAC does not hand out DNS information (or any Windows domain specific info).

You get an address, a fixed subnet, and a default gateway. Period. This doesn't make it entirely useless, but definitely SLAAC is not a DHCP killer.

To enable a Cisco router to being making SLAAC announcements, all you need to do is configure an interface with an IPv6 address and a /64 subnet:

interface GigabitEthernet0/2
no ip address
duplex auto
speed auto
ipv6 address 2001:1890:1208:240::1/64

This line:

ipv6 address 2001:1890:1208:240::1/64

causes the router to begin making ND announcements which permit other devices to SLAAC themselves. We can verify announcements with a show ipv6 interface:

V6-R1-2911#sh ipv6 int gi0/1
GigabitEthernet0/1 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::xxxx:xxxx:xxxx:xxxx
No Virtual link-local address(es):
Global unicast address(es):
   2001:xxxx:xxxx:xxxx::1, subnet is 2001:xxxx:xxxx:xxxx::/58
Joined group address(es):
   FF02::1
   FF02::2
   FF02::1:FF00:1
   FF02::1:FFFD:CCC1
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ICMP unreachables are sent
ND DAD is enabled, number of DAD attempts: 1
ND reachable time is 30000 milliseconds (using 30000)
ND advertised reachable time is 0 (unspecified)
ND advertised retransmit interval is 0 (unspecified)
ND router advertisements are sent every 200 seconds
ND router advertisements live for 1800 seconds
ND advertised default router preference is Medium
Hosts use stateless autoconfig for addresses.
V6-R1-2911#

So you've got IPv6...

...now what?

This site contains a list of websites with verified IPv6 connectivity. Regularly updated and tested. Also provides the resolved IPv6 address so you can perform basic ping testing in case your DNS is flaky (anyone else have this problem?).

Global IPv6 Deployment Progress Report

Haven't ruled out a problem on the local end, but we do get better (but not 100%) responses from:

Public DNS servers:

	IPv6	IPv4
Open DNS	2620:0:ccc::2 2620:0:ccd::2	208.67.222.222 208.67.220.220
Google Public DNS	2001:4860:4860::8888 2001:4860:4860::8844	8.8.8.8 8.8.4.4