Sup 2TXL fabric speed 20G only

[wavecomas]

Hi!

Can anyone please help to clarify why Sup 2TXL fabric speed shows 2x20G only, while WS-X6904-40G  shows 2x40G like expected ?  Switch chassis is 6504-E.

adala-gw#sh fabric status
slot channel speed module fabric hotStandby Standby Standby
status status support module fabric
1 0 20G OK OK N/A
1 1 20G OK OK N/A
3 0 40G OK OK Y(not-hot)
3 1 40G OK OK Y(not-hot)

adala-gw#sh module
Mod Ports Card Type Model Serial No.
--- ----- -------------------------------------- ------------------ -----------
1 5 Supervisor Engine 2T 10GE w/ CTS (Acti VS-SUP2T-10G SAL1834Z38M
3 20 DCEF2T 4 port 40GE / 16 port 10GE WS-X6904-40G SAL1828WCJZ

Mod MAC addresses Hw Fw Sw Status
--- ---------------------------------- ------ ------------ ------------ -------
1 6c41.6a0c.7a7f to 6c41.6a0c.7a86 2.1 12.2(50r)SYS 15.5(1)SY Ok
3 f8c2.884b.3f60 to f8c2.884b.3f73 1.1 12.2(50r)SYL 15.5(1)SY Ok

Mod Sub-Module Model Serial Hw Status
---- --------------------------- ------------------ ----------- ------- -------
1 Policy Feature Card 4 VS-F6K-PFC4XL SAL1832Y503 2.1 Ok
1 CPU Daughterboard VS-F6K-MSFC5 SAL1833YV6M 3.0 Ok
3 Distributed Forwarding Card WS-F6K-DFC4-EXL SAL1832XYPV 1.2 Ok

Mod Online Diag Status
---- -------------------
1 Pass
3 Pass

[Reza Sharifi]

Hi,

The crossbar fabric consists of 18 fabric channels, providing each linecard two fabric channels into the crossbar fabric. These channels can run at 8Gbps or 20Gbps depending upon the line card used. The CEF256 and dCEF256 series modules connect to fabric using 8 Gbps per channel and CEF720 series modules connect to it using 20 Gbps per channel.

see this link for further details:

https://community.cisco.com/t5/networking-documents/switch-fabric-troubleshooting-tips/ta-p/3110265

HTH

[Scott Hodgdon · Accepted solution]

wavecomas,

See Figure 2 athttps://www.cisco.com/c/en/us/products/collateral/switches/catalyst-6500-series-switches/white_paper_c11-676346.html .

Notice there are 2 connections to the Crossbar Switch Fabric (Fabric Intf 0 and 1). This is what you see in your output.

Why are they 20Gbps? Well, the Sup2T has just 2x10G and 3x1G uplinks, so when we designed the module we figured most people would use the 2x10Gbps uplinks but both of them would never be 100% utilized in the real world (maybe in labs) so we opted for a 20Gbps connection for Fabric Intf 0 that supports the uplinks.

Fabric Intf 1 connects to hte Bus (16Gbps maximum) and MSFC 5 (1Gbps maximum), so more than 20Gbps was not needed.

Since the PFC4 only does lookups of packet headers which are very small, we did not need a lot of bandwidth there.

if you want a deeper look, check out ciscolive.com and search for BRKARC-3465 in the On-Demand Library (this is a free resource available to you even if you never went to a Cisco Live). It is a deep dive on Cat 6K.

Cheers,

Scott Hodgdon