Understanding Additional interfaces on stacked switch - 24 ports switch (Cisco Catalyst 2960XR-24TD-I)

[SJ K]

Hi all,

I have 2 x 2960XR stacked.
During a show version, and show ip int br, i am seeing the following

4 Virtual Ethernet interfaces
1 FastEthernet interface
52 Gigabit Ethernet interfaces
4 Ten Gigabit Ethernet interfaces

===========================================================

GigabitEthernet1/0/25  unassigned      YES unset  down                  down
GigabitEthernet1/0/26  unassigned      YES unset  down                  down
Te1/0/1                unassigned      YES unset  down                  down
Te1/0/2                unassigned      YES unset  down                  down

GigabitEthernet2/0/25  unassigned      YES unset  down                  down
GigabitEthernet2/0/26  unassigned      YES unset  down                  down
Te2/0/1                unassigned      YES unset  down                  down
Te2/0/2                unassigned      YES unset  down                  down 

============================================================

I have 2 x SFP+ port per switch with no modules inserted.

Q1) I believe the 1 x FastEthernet interface is the management interface (it is 1 , since it is stacked) - am i right ?

Q2) What is the 4 x Virtual Ethernet interfaces for ? Where can i see it ?

Q3) I have only 24 physical gigabit ethernet ports, where is interface 25/26 on each member coming from ?

Q4) Is the 10 gigabit interface referring to the SFP+ port ?  I have no modules inserted, will it still show the interface ?

Lastly, I have tried to search around in the product documentation with regards to the interfaces information in cisco but to no avail. This is my 1st time handling cisco switch, i would greatly appreciate if some kind soul can point me to the right direction on the document which discussed on the inerfaces above. (the installation guide does not talk mentioned about the interfaces)

Thank you!

[Leo Laohoo]

Q1) I believe the 1 x FastEthernet interface is the management interface (it is 1 , since it is stacked) - am i right ?

the entire stack can only have 1 management interface.

where is interface 25/26 on each member coming from ?

SFP/SFP+ ports. 

Is the 10 gigabit interface referring to the SFP+ port ?  

Yes.

I have no modules inserted, will it still show the interface 

Yes.

[SJ K]

Hi Leo,

Nice to hear from you again.

You mentioned that 

- interface 25/26 are coming from the SFP/SFP+ port but the
- 10 gigabits ports (Te1/0/1, Te1/0/2 ) are also refering to the SFP/SFP+ port

q1) I have only 2 SFP/SFP+ interfaces per switch, why is it showing 4 interfaces then ?  Does it mean if i have 1gb module insert, then i will use 25/26 ? if i have 10gb module inserted then i will use  the 10gb interfaces ?

q2) Any idea what are the 4 virtual Ethernet interfaces ?

Regards,

Noob

[Leo Laohoo]

q1) I have only 2 SFP/SFP+ interfaces per switch, why is it showing 4 interfaces then ?  Does it mean if i have 1gb module insert, then i will use 25/26 ? if i have 10gb module inserted then i will use  the 10gb interfaces ?

Depending on the IOS codes, the answer is YES.  

When I mean "Depending on the IOS code", this means there are some IOS bugs which won't "switch" from TenGigabitEthernet to GigabitEthernet based on the type of module inserted.  

q2) Any idea what are the 4 virtual Ethernet interfaces ?

SFP and SFP+ ports.  

[SJ K]

Hi Leo,

It means that for the 2 x SFP/SFP+ interface that I have on each switch member ->

I would have 4 interfaces - Ge1/0/25, Ge1/0/26, Te1/0/1, Te1/0/2 ? and if i have inserted a 1GB module, setting it on the Te1/0/1 won't work.

========================

What about the 4 virtual Ethernet interfaces in which you mentioned are the SFP and SFP+ ports as well ?   What are they use for ?

So in total i would have a total of 6 interfaces  ( 2 x 1gb, 2 x 10gb, 2 x VirtualEthernet ?)

for 2 physical interface (SFP/SFP+) interfaces?

Regards,

Noob

[Leo Laohoo · Accepted solution]

I would have 4 interfaces - Ge1/0/25, Ge1/0/26, Te1/0/1, Te1/0/2 ? and if i have inserted a 1GB module, setting it on the Te1/0/1 won't work.

That's correct.  They're called "dual-personality" ports but you can only use one (SFP or SFP+).

So in total i would have a total of 6 interfaces  ( 2 x 1gb, 2 x 10gb, 2 x VirtualEthernet ?)

I think the virtual ethernet are the two PHYSICAL ports.  Each port can do SFP/SFP+ so each physical port is two virtual ethernet ports.

[SJ K]

Hi Leo,

I have 2 x SFP/SFP+ port on each switch, so if as per what you meant "each physical port = 2 virtual ethernet port", then i would have 4 virtual ethernet port per switch.

And in total since i have 2 switch stacked, I should have 8 virtual ethernet port, but it is only showing 4 Virtual Ethernet interfaces

Regards,

Noob