Max FEX with Nexus 5000 VPC Pair

[mazhar mahadik]

Hi Experts,

what is the number of  maximum  fex(2K)  i can connect to nexus 5000 vpc pair, with L3 functionality on 5000

1) if i connect each fex dual hommed to both 5000

2) if i connect each fex single hommed to only 1 5000.

Thanks.

[Leo Laohoo · Accepted solution]

Cisco Nexus 2000 Series Fabric Extenders Data Sheet

Table 2

• Up to 12 fabric extenders per Cisco Nexus 5010P and Nexus 5020P Switch.
• Up to 24 fabric extenders per Cisco Nexus 5548P, Nexus 5548UP, or Nexus 5596UP Switch (16 fabric extenders for Layer 3 configurations).

[anthonykahwati]

Hi there

I am looking at trying to go against this and just wonder if the information given is from testing, or, just Cisco recommendation?

I want to deploy 18 FEX 2K, dual homed to 2 x 5596 (using L3 module) but I only want them to have one link back to each 5K, not 2.

Does anyone know what actually happens, if anything at all, if you push passed 16 in dual homed dployments?

The main reason I ask is because with cisco expecting each FEX to have 40Gb to the 5K, that is 24 x 2K at 4 ports each, which is the full 96 used with nothing spare. I am wondering if it is just a guideline?

Any one know?

Many thanks

Anthony

[Andras Dosztal]

It doesn't matter if the FEXes are single or dual-homed, the maximum is always what leolaohoo said.


Sent from Cisco Technical Support Android App

[anthonykahwati]

Thanks for the reply Andras.... any idea what happens if you go above?

[mazhar mahadik]

Many Thanks  Leo & Andras.

[Leo Laohoo]

Thanks for taking the time to rate our posts.

[Steve Fuller]

Hi guys,

Bit of an update on this. The maximum number of supported FEX is not the same for straight-through and dual-homed FEX.

From the Enhanced vPC Scalability section of the Cisco Nexus 5000 and 6000 Series NX-OS Interfaces Operations Guide:

From the Cisco NX-OS 5.1(3)N1(1) release and later releases, each Cisco Nexus 5500 Series device can manage and support up to 24 FEXs without Layer 3. With Layer 3, the number of FEXs supported per Cisco Nexus 5500 Series device is 8. With Enhanced vPC and a dual-homed FEX topology each FEX is managed by both Cisco Nexus 5000 Series devices. As a result, one pair of Cisco Nexus 5500 Series devices can support up to 24 FEXs and 16 FEXs for Layer 2 and Layer 3.

There are differences in scalability between the straight-through topology, the dual-homed FEX topology, and the Enhanced vPC topology. In the straight through topology, only one Cisco Nexus 5000 Series device manages each FEX and a pair of Cisco Nexus 5500 Series devices manage up to 48 FEXs.

This is also shown in Table 1 of the Verified Scalability for Cisco Nexus 5500 Series document which states:

Maximum FEXs per Cisco Nexus 5500 Series Switch: 24

Maximum FEXs dual homed to a vPC Cisco Nexus 5500 Series Switch Pair: 24

I think the wording in the scalability document might be open to interpretation, but the wording and diagram from the interface operations guide is pretty clear.

Regards

[mazhar mahadik]

Thanks Steve,

Thanks for the update Steve , Much Appreciated.

[Leo Laohoo]

I think the wording in the scalability document might be open to interpretation

Thanks for the update.  Yeah.  The wording is very confusing.

[steve.blunt]

Hi can I just clarify the following?

In respect to Layer 3, is this a blanket restriction?

For example a pair of Nexus 5548UP deployed as a pair can support a maximum of 16 Fexs if static IP routes are used, or is the restriction only applicable to when the Layer 3 daughter card is installed and a dynamic routing protocol is in use?

Also in the same deployment i.e. a pair of Nexus 5548UP, can 24 Fexs in layer 2 only mode be supported plus a further 16 in layer 3?

[Reza Sharifi]

Just FYI and in addition to what Steve said the same limitations apply to the 6000 series. If you dual home your FEX as layer 2 the max is 48 (for 2 6000) if you use them as layer 3 the Max is 24

Reza

Sent from Cisco Technical Support iPhone App

[Reza Sharifi]

Layer3 (SVI)

Sent from Cisco Technical Support iPhone App