An Epyc new addition to the UCS Family!

Another great post from UCS Guru. Make sure you read the full story on his blog.

UCSguru.com

Back in February of this year, when I read an article in The Register, announcing that Raghu Nambiar, the then chief technology officer for UCS servers had joined AMD. I didn’t think too much of it, but when I also saw that AMD were, for the first time (in my memory), exhibiting at Cisco Live, My right eyebrow rose in a particular “Roger Moore esque” manner, and I sensed something may well be afoot.

Some of you may well have noticed that even since 2009 there has always been an AMD CPU server qualification policy in Cisco UCS Manager , and several years ago I did bring this up with Cisco, as to why in an exclusively Intel based product would need such a policy, to which, if memory serves, the answer at the time was “never say never”

Well today that “prophecy”  was fulfilled with the announcement of the…

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Posted in GNS3 WorkBench

Backup Plan

Found this in a hotel tonight. Always good to have a backup plan

Posted in GNS3 WorkBench | Tagged

Why Easter doesn’t it fall at different times in different time zones

If Easter Sunday falls “on the first Sunday AFTER the first full moon after the vernal equinox”, why doesn’t it fall at different times in different time zones?  This year for example, tonight’s (Easter Saturday March 31 2018) full moon occurs after midnight in places between the International date line and the UTC+11 time zone. So according to the formula, Kiwi kids should have to wait another week before breaking open those chocolate eggs.

Well, it turns out that the formula is not set by the astronomical path of the moon, but by a bunch of men (I’ve no doubt women weren’t invited) who formulated the Ecclesiastical Lunar Calendar so long ago that it was before the split of the Gregorian and Julian calendars. (In 325 AD/CE in fact).

Which means today we actually have two Easters, one for each of the divergent calendars, even though both follow the same formula.

Anyway, in the said Ecclesiastical Lunar Calendar, the vernal equinox is always March 21, irrespective of the position of the earth in regard to its transit around the sun. And Easter is always the Sunday following the Pascal Full Moon. And for the calculation of Easter, the Pascal Full moon is defined as been the 14th day after the Ecclesiastical Lunar new moon – so we are back to the Ecclesiastical Lunar Calendar and its ancient origins.

Now it’s probably a good thing that there is a universal standard or two, it means we only have two variations – the Gregorian and the Julian – of Easter throughout the world, and children in New Zealand, Fiji etc. don’t have to hang out for another week to get their Easter Eggs – oh that’s unless they are following the Julian calendar (as Orthodox Christians do), it which case they will have to wait until April 8 2018!

RedNectar

Posted in blog, opinion

CSMA/CD and full duplex for wireless? It could be coming

A group of researchers at National Instruments have found a way to listen to radio signals while receiving on the same frequency.

The team found a solution that relies on in-band full duplex, so it can sense while transmitting, which potentially eliminates all collision overheads in wireless networks.

This could have huge implications – and even give your home wifi a boost if you have a lot of users – certainly will give the office and cafe wifi hotspots a boost.

The problem with existing wireless communications is that once a device starts transmitting, it doesn’t know if another device has transmitted at the same time (causing a collision) until it has finished transmitting and waited for an acknowledgement from the Access Point.  If no acknowledgement comes, it tries again. This is called Carrier Sense, Multiple Access with Collission Avoidance (CSMA/CA).

Your ancient (1980-c2000) shared Ethernet on the other hand operated in much the same way, a device would start transmitting, but was able to detect if any other device transmitted at the same time, and so stop transmitting immediately. This was called  Carrier Sense, Multiple Access with Collission Detection (CSMA/CD) and is course much more efficient than Collision Avoidance.

But that is not the whole story. Modern wired Ethernet networks use two pairs of wires to transmit, and another to recieve, meaning they can transmit AND receive at the same time. Full Duplex.  If we could do that for wireless, (and this article indicates that they have achieved full-duplex operation albeit with just 6 devices at this stage), then the benefits could be much greater.

RedNectar

Posted in blog, opinion, wifi, wireless network | Tagged ,

Why have WordPress made it soooo hard to follow someone?

WordPress, you have hosted my blog since 2010.  I won’t start a tirade of things you STILL can’t do on WP, but I am going to have a whinge about one feature you have obscured.

Why have WordPress made it soooo hard to follow someone?  I should never have to respond to a reader’s comment such as the one I got today.

I would like to thank you sooooo much for such a awesome ACI blogs, I found things here which are not well documented even in Cisco Docs. You are surely doing a great job. I wish to find a subscriber button on your website and keep up with your great work.

For those who would like to follow my blog, or any other wordpress.com blog, you have to move your cursor to the bottom right-hand corner of the page, and/or scroll up a bit (scrolling is clearly the only option on a mouseless device). You will then get an option pop up giving you the chance to follow or subscribe to my blog.

folllow-subscribe

Posted in opinion, rant, wordpress | Tagged | 2 Comments

RedNectar’s HX Pre-Install Checklist

…has been updated and is found here: https://rednectar.net/2018/10/06/rednectars-hyperflex-pre-install-checklist-updated/

Posted in Cisco, Data Center, Data Centre, Hyperflex, UCS | Tagged , , ,

ISIS, COOP, BGP and MP-BGP in Cisco ACI

Note: This post started as an answer I gave on the Cisco Support Forum. This version is slightly expanded with pictures and examples.

In this post I will examine the roles of three very important protocols that exist in the ACI environment.

I will explain

  • that IS-IS is the underlying routing protocol that is used by the leaves and spines to learn where they sit in the topology in relation to each other
  • how Leaf switches use COOP to report local station information to the Spine (Oracle) switches
  • how BGP and MP-BGP is used to redistribute routes from external sources to leaf switches.

Let me start with a picture.  Imagine a simple 2leaf/2spine topology with HostA attached to to Leaf1 and with HostB attached to to Leaf2.

  • Leaf1 has a VTEP address of 10.0.1.101
  • Leaf2 has a VTEP address of 10.0.1.102
  • Spine1 has a VTEP address of 10.0.1.201
  • Spine2 has a VTEP address of 10.0.1.202
  • HostA has a MAC address of A and an IP address of 192.168.1.1 and is attached to port 1/5 on Leaf1
  • HostB has a MAC address of B and an IP address of 192.168.1.2 and is attached to port 1/6 on Leaf2

Enter IS-IS

The leaves and spines will exchange IS-IS routing updates with each other so that Leaf1 sees that it has two equally good paths to reach Leaf2, and Leaf2 sees that it has two equally good paths to reach Leaf1.


Leaf1# show ip route vrf overlay-1 10.0.1.102
IP Route Table for VRF "overlay-1"

10.0.1.102/32, ubest/mbest: 2/0
*via 10.0.1.201, eth1/51.2, [115/3], 6d20h, isis-isis_infra, L1
*via 10.0.1.202, eth1/52.2, [115/3], 6d20h, isis-isis_infra, L1

For now, that’s all we need to know about IS-IS – it is the routing protocol used by the VTEPs to learn how to reach the other VTEPs.

Now think about the hosts.

This is where COOP comes in.

When Leaf1 learns about HostA because, say HostA sent an ARP request seeking the MAC address of 192.168.1.2 (which you know is HostB, but that’s not relevant at the moment), Leaf1 looks at that ARP request, and just like a normal switch, learns that MAC A is present on port 1/5.  But the leaf is a bit more clever than that, and looks INSIDE the payload of the ARP packet and learns that Host1 also has an IP address of 192.168.1.1 and records all this information in its Local Station Table.

Leaf1#show endpoint interface ethernet 1/5

VLAN/Domain  Encap VLAN  MAC/IP Address  Interface
+-----------+----------+----------------+---------
65           vlan-2051  a036.9f86.e94e L eth1/5
Tenant1:VRF1 vlan-2051  192.168.1.1    L eth1/5

AND THEN reports this information to one of the spine switches (chosen at random) using the Council Of Oracles Protocol (COOP).  The spine switch (oracle) that was chosen then relays this information to all the other spines (oracles) so that every spine (oracle) has a complete record of every end point in the system.

The spines (oracles) record the information learned via the COOP in the Global Proxy Table, and this information is used to resolve unknown destination MAC/IP addresses when traffic is sent to the Proxy address.

Note that all of this happens without anything to do with BGP.

But to round off the COOP story, we would assume that at some stage Leaf2 (a citizen) will also learn HostB‘s MAC and IP and also inform one of the spines (oracles) at random of this information using the COOP.

Spine1#show coop internal info repo ep | egrep -i "mac|real|-"
------------------------------------------
EP mac : A0:36:9F:86:E9:4E
MAC Tunnel : 10.0.1.101
Real IPv4 EP : 192.168.1.1
------------------------------------------
EP mac : A0:36:9F:61:88:FD
MAC Tunnel : 10.0.1.102
Real IPv4 EP : 192.168.1.2

So COOP is used solely for the purpose of distributing endpoint information to spine switches (oracles). As far as I know, spine switches never use COOP to distribute end host information to leaf switches.

So where does BGP fit in?

BGP is not needed until an external router is connected.  So now imagine that Leaf2 has had a router connected and has learned some routes from that external router for a particular VRF for a particular Tenant.

How can Leaf2 pass this information on to Leaf1 where HostA is trying to send packets to one of these external networks?  For Leaf2 to be able to pass routing information on to Leaf1 and keep that information exclusive to the same VRF, we need a routing protocol that is capable of exchanging routing information for multiple VRFs across an underlay network

Which is exactly what MP-BGP was invented for – to carry routing information across MPLS underlay networks.  In the case of ACI, BGP is configured by choosing an Autonomous System number and nominating one of the spine switches to be a route reflector.  MP-BGP is self configuring, you don’t need to do anything to make it work!

(Although you will have to configure your Tenant to exchange routes with the external router.)

Leaf1# show ip route vrf Tenant1:VRF1

192.168.1.0/24, ubest/mbest: 1/0, attached, direct, pervasive
*via 10.0.1.102%overlay-1, [1/0], 04:43:32, static, tag 4294967295
192.168.1.10/32, ubest/mbest: 1/0, attached, pervasive
*via 192.168.1.10, vlan25, [1/0], 03:52:23, local, local
1.0.0.0/8, ubest/mbest: 1/0
*via 10.0.1.102%overlay-1, [200/5], 00:11:41, bgp-1, internal, tag 1

RedNectar
aka Chris Welsh

Posted in ACI, ACI configuration, APIC, Cisco, Data Center, Data Centre, EPG, L3 Out, L3out | Tagged , ,