topic RE: BCB VS BEB in ExtremeSwitching (VSP/Fabric Engine)

BCB VS BEB

ThorF — Wed, 20 Jul 2022 15:18:00 GMT

Can a BCB have UNI ports and still work as a BCB?

RE: BCB VS BEB

Adam_Minowski — Thu, 21 Jul 2022 09:28:00 GMT

Hi,

BCB is a switch without UNI ports - it has only NNI ports active - simple as that. If you terminate the user traffic there, then it becomes BEB. On the other hand it does not change much from fabric perspective. You can have the network with BEBs only - in fact this is the beauty and flexibility of fabric connect. The only drawback is that you need to configure services in the core, so it destroys "do not touch the core" concept.

RE: BCB VS BEB

ThorF — Thu, 21 Jul 2022 11:13:00 GMT

In picture 1 everything works fine when the box in the middle is a BCB.
In picture 2 i have connected a end device to the box in the middle so it becomes a BEB.

To make thinks work in picture 2 i have to define the i-sid on the middle box. Does not a BEB handle traffic like a BCB? Why?

RE: BCB VS BEB

WillyHe — Thu, 21 Jul 2022 12:32:00 GMT

Hello,

The "general" idea is to construct a FC network with BCB functionality in the backbone and BEB functionality at the edge.
This way you create a very stable backbone network, only SPBM/ISIS L2 routing is enabled.
Extra advantage is that there is no license needed on BCB switches to e.g. use VRF/L3-VSN because they are not "IP routing aware", they just perform L2 forwarding.

regards
WillyHe

RE: BCB VS BEB

Adam_Minowski — Thu, 21 Jul 2022 14:34:00 GMT

Yes in order to provide any EDGE service on your middle switch you need to have:
1. Some Gix/y port configured (with flex uni enable) - it is your UNI port
2. I-sid created - as you have on the picture (i-sid 200960 elan)
3. Map i-sid to vlan/port (c-vid 960 port Gix/y). Exacly the same as for other BEBs.
Alternatively you can connect a device (PC) which does not do the vlan tagging by default:

i-sid 200960 elan
(elan:200960)# untagged-traffic port Gix/y
In this way your PC will be a member of same L2 domain as the rest devices in vlan 960.

The config you provided on second picture does not make any sense. You just created local i-sid 200960 but no UNI port (vlan/port mapping) is configured. I-SID creation makes sense only when you terminate end user traffic on that particular node.

I don't know how to respond to your "why" question. BCB and BEB describes only characteristics/use-case of fabric node. Fabric node with UNI ports is called BEB as it terminates edge/customer traffic and do the MacInMac encapsulation. BCB is a fabric node which does not terminate any edge traffic - it has only NNI ports and it passess traffic already encaplsulated by BEBs. So you can imagine that BEB is doing more job because it has to encapsulate packets into MacInMac and then pass it to the next node - doest not matter if it's BEB or BCB. Technically the difference is just in configration. You can have multiple BCBs in your network when needed, but as well you can have no BCB in your network - only BEBs. If you think about BCB as some really special fabric node which cannot terminate user traffic - you're wrong.

For spine and leaf architectures in IP fabric, it is true that spine cannot terminate user traffic as fabric node usage is strictly limited by design. But it does not apply to fabric connect (spbm fabric).

Hope it helps.

Adam

RE: BCB VS BEB

ThorF — Thu, 21 Jul 2022 15:11:00 GMT

Ok, so it does not matter if the box in the middel is BCB og BEB? I could not pass traffic without defineing the i-sid on the middle box?
My lab is more complex than this, so probably something else is wrong.

RE: BCB VS BEB

Adam_Minowski — Thu, 21 Jul 2022 17:22:00 GMT

The whole point in fabric is to configure service on the edge ONLY. BCB is just a transport and you typically do not configure anything on it - except SPBM

If you can't pass traffic between devices than most probably you:
a. did not configure SPBM on the nodes properly, and/or
b. did not enable Gi ports (in older voss versions all ports are disabled by default!!), and/or
c. did not configure Gi0/1 edge ports properly (encapsulation dot1q, flex-uni enable etc), and/or
d. did not configure end-system device properly (it does not do vlan tagging for example), and/or

To configure SPBM on nodes use this on each switch:
enable
config terminal
run spbm
And go through wizard.

Afterwards you need to see neigbors when you do:

show isis adjacencies

In your case when ran on BCB, you should see two neighbors BEB1 and BEB2 (similar to example below):

==================================================================================================================================
ISIS Adjacencies
==================================================================================================================================
INTERFACE L STATE UPTIME PRI HOLDTIME SYSID HOST-NAME STATUS AREA AREA-NAME
----------------------------------------------------------------------------------------------------------------------------------
Port1/1 1 UP 8d 23:00:15 127 18 020d.0211.0010 L2-D1-1 ACTIVE HOME
Port1/2 1 UP 8d 22:59:55 127 20 020d.0211.0020 L2-D1-2 ACTIVE HOME